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150 Cards in this Set
- Front
- Back
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What is a neighbor table?
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Is a list of connected OSPF speakers (devices running OSPF) which is built up by exchanging hello messages. OSPF sends out hellos every 10 secs on broadcast links and every 30 secs on non-broadcast links
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Class A first octet
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1-126
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What is the Class C address range in decimal and in binary?
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192–223, 110xxxxx
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What are the formal states a neighbor relationship transitions through in the process of forming a full adjacency?
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Down=no info/hellos received, Init=Has received a hello but no RID, 2 way=bi-directional communication has been established, Exstart=DR & BDR are elected, Exchange=Exchange Database Descriptor packets (DDP), Loading=Exchange of Link-state info, Full=Routers are fully adjacent, all router and network LSAs are exchanged and the router databases are fully synchronized
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Class B first octet
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128-191
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What layer of the DoD model is equivalent to the Transport layer of the OSI model?
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Host-to-Host
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What is a Designated Router and a Backup Designated Router?
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On a broadcast segment a BR is the 1 router assigned the duty of maintaining adjacencies with all other segment routers. It reduces the number of adjacencies which reduces b/w use. Routers advertise changes to the "all DRs" multicast address 224.0.0.6, and DRs advertise the LSA using the "ALL SPF" multicast address of 224.0.0.5. For redundancy a BDR is also elected
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How is the router-id of an OSPF Router chosen?
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1. via router-id command. if not used then:
2. Highest Loopback interface IP. If no loopbacks then: 3. Highest physical interface IP. |
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Class C first octet
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192-223
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What is the valid range of a Class A network address?
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1–126
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What is an OSPF area?
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It is a logical grouping of routers that are running OSPF with identical topological databases. Each area runs SPF separately and summaries are passed between each area
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How do you get OSPF to recognize a new router-id?
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either reset the router or restart the ospf process using:
clear ip ospf process. |
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Class A valid network numbers
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1.0.0.0 to 126.0.0.0
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What is the 127.0.0.1 address used for?
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Loopback or diagnostics
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OSI Model: Physical Layer
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the electrical, mechanical, procedural, and functional specifications for activating, maintaining, and deactivating the physical link between communicating network systems. Physical layer specifications define characteristics such as voltage levels, timing of voltage changes, physical data rates, maximum transmission distances, and physical connectors. Physical layer implementations can be categorized as either LAN or WAN specifications.
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What are the default OSPF Hello timers?
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Broadcast & Point-to-Point: 10 seconds
NBMA: 30 seconds |
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Class B valid network numbers
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128.0.0.0 to 191.255.0.0
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How do you find the network address from a listed IP address?
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Turn all host bits off.
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How do you find the broadcast address from a listed IP address?
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Turn all host bits on.
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OSI Model: Data Link Layer
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provides reliable transit of data across a physical network link. Different data link layer specifications define different network and protocol characteristics, including physical addressing (ie MAC addresses), network topology (bus, ring), error notification, sequencing of frames, and flow control. split into Logical Link Control (LLC) and Media Access Control (MAC)
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What hello values must match in order for an OSPF neighbor relationship to form?
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Hello & Dead Timers
Subnet mask area id area stub flag setting authentication password |
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Class C valid network numbers
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192.0.0.0 to 223.255.255.0
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What is the Class B private IP address space?
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10.0.0.0 through 10.255.255.255
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What is the role of an Area Border Router (ABR)?
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Is responsible for connecting 2 or more areas. It holds a full topology database for each area to which its connected and sends LSA updates between the areas. These LSA updates are summary updates of the subnets within an area, but are sent as Type 3 LSAs only if summarization is configured on the ABR.
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How is the dead timer calculated?
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4 * Hello.
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What is the Class C private IP address space?
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172.16.0.0 through 172.31.255.255
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OSI Model: Data Link Layer: Logical Link Control Layer
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manages communications between devices over a single link of a network.IEEE 802.2. supports both connectionless and connection-oriented services
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What are all the available characters that you can use in hexadecimal addressing?
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192.168.0.0 through 192.168.255.255
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What is a Autonomous System Boundary Router (ASBR)?
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They are typically located in the backbone area and connect to other routing domains. e.g. to internet or EIGRP
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What are all the available characters that you can use in hexadecimal addressing?
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0–9 and A, B, C, D, E, and F
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OSI Model: Data Link Layer: Media Access Control Layer
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manages protocol access to the physical network medium. IEEE MAC specification defines MAC addresses
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What is the significance of the master/slave designation in ospf neighbor relationships
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master sends his dbd first.
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What are the decimal and hexadecimal equivalents of the binary number 10011101?
(Choose two.) A. 159 B. 157 C. 185 D. 0x9D E. 0xD9 F. 0x159 |
B, D. To turn a binary number into decimal, you just have to add the values of each bit that
is a 1. The values of 10011101 are 128, 16, 8, 4, and 1. 128 + 16 + 8 + 4 + 1 = 157. Hexadecimal is a base-16 number system. The values of hexadecimal are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F—16 characters total, from which to create all the numbers you’ll ever need. So, if 1001 in binary is 9, then the hexadecimal equivalent is 9. Since we then have 1101, which is 13 in binary, the hexadecimal answer is D and the complete hexadecimal answer is 0x9D. Even though binary/hex numbers were discussed in Chapter 1, a good review is necessary here. |
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OSI Model: Network Layer
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defines the network address. defines the logical network layout. IP lives here.
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What happens between neighbors in the OSPF loading state
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master & slave ack sent dbd's.
1. slave sends LSRs for unknown routes 2. master responds to LSR's with LSU's. 3. master sends LSRs for unknown routes 4. slave responds to LSR's with LSU's. |
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Private Address space class A - Network numbers and # of networks each
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a=10.0.0.0 1 network
b= 172.16.0.0 to 172.31.0.0 16 networks, c= 192.168.0.0 to 192 168 255.0.0 256 networks |
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Which of the following allows a router to respond to an ARP request that is intended for a
remote host? A. Gateway DP B. Reverse ARP (RARP) C. Proxy ARP D. Inverse ARP (IARP) E. Address Resolution Protocol (ARP) |
C. Proxy ARP can help machines on a subnet reach remote subnets without configuring routing
or a default gateway. |
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Packet
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A logical grouping of information that includes the network layer header and encapsulated data, but specifically does not include any headers and trailers below the network layer
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You want to implement a mechanism that automates the IP configuration, including IP
address, subnet mask, default gateway, and DNS information. Which protocol will you use to accomplish this? A. SMTP B. SNMP C. DHCP D. ARP |
C. Dynamic Host Configuration Protocol (DHCP) is used to provide IP information to hosts
on your network. DHCP can provide a lot of information, but the most common is IP address, subnet mask, default gateway, and DNS information. |
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OSI Model: Transport Layer
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TCP & UDP live here. segments the data for transport across the network. responsible for making sure that the data is delivered error-free and in the proper sequence. Flow control. Virtual circuits are established, maintained, and terminated by the transport layer. error checking, error recovery.
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What protocol is used to find the hardware address of a local device?
A. RARP B. ARP C. IP D. ICMP E. BootP |
B. Address Resolution Protocol (ARP) is used to find the hardware address from a known
IP address. |
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What is an Area ID?
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Is a mechanism of grouping routers that share full knowledge of OSPF-derived routes within that OSPF area.
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How does an ospf router communicate with its DR?
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Via multicast address 224.0.0.6
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Which of the following are layers in the TCP/IP model? (Choose three.)
A. Application B. Session C. Transport D. Internet E. Data Link F. Physical |
A, C, D. This seems like a hard question at first because it doesn’t make sense. The listed
answers are from the OSI model and the question asked about the TCP/IP protocol stack (DoD model). However, let’s just look for what is wrong. First, the Session layer is not in the TCP/ IP model; neither are the Data Link and Physical layers. This leaves us with the Transport layer (Host-to-Host in the DoD model), Internet layer (Network layer in the OSI), and Application layer (Application/Process in the DoD). |
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Protocol data unit (PDU)
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An OSI term to refer generically to a grouping of information by a particular layer of the OSIO mode. More specifically, an LxPDU would imply the data and headers as defined by Layer x.
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Which class of IP address provides a maximum of only 254 host addresses per network ID?
A. Class A B. Class B C. Class C D. Class D E. Class E |
C. A Class C network address has only 8 bits for defining hosts: 28 – 2 = 254.
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OSI Model: Session Layer
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establishes, manages, and terminates communication sessions. Some examples of session-layer implementations include Zone Information Protocol (ZIP), the AppleTalk protocol ; and Session Control Protocol (SCP), the DECnet Phase IV session layer protocol.
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Which of the following describe the DHCP Discover message? (Choose two.)
A. It uses FF:FF:FF:FF:FF:FF as a layer 2 broadcast. B. It uses UDP as the Transport layer protocol. C. It uses TCP as the Transport layer protocol. D. It does not use a layer 2 destination address. |
A, B. A client that sends out a DHCP Discover message in order to receive an IP address
sends out a broadcast at both layer 2 and layer 3. The layer 2 broadcast is all Fs in hex, or FF:FF:FF:FF:FF:FF. The layer 3 broadcast is 255.255.255.255, which means all networks and all hosts. DHCP is connectionless, which means it uses User Datagram Protocol (UDP) at the Transport layer, also called the Host-to-Host layer. |
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What is the Transmit timer and its default setting?
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Determines the estimated number of seconds that it takes to send an LSA to a neighbor. Default is 1 sec.
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Which layer 4 protocol is used for a Telnet connection?
A. IP B. TCP C. TCP/IP D. UDP E. ICMP |
B. Although Telnet does use TCP and IP (TCP/IP), the question specifically asks about layer 4,
and IP works at layer 3. Telnet uses TCP at layer 4. |
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How do you keep your router from being elected DR or BDR
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under the interface or subinterface running ospf,
ip ospf priority 0 |
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Segment
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In TCP, a term used to describe a TCP header and its encapsulated data (also called an L4PDU). Also in TCP, the process of accepting a large chunk of data from the application layer and breaking it into smaller pieces that fit into TCP segments. In Ethernet, a segment is either a single Ethernet cable to a single collision domain (no matter how many cables are used).
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Which statements are true regarding ICMP packets? (Choose two.)
A. They acknowledge receipt of a TCP segment. B. They guarantee datagram delivery. C. They can provide hosts with information about network problems. D. They are encapsulated within IP datagrams. E. They are encapsulated within UDP datagrams. |
C, D. Internet Control Message Protocol (ICMP) is used to send error messages through the
network, but they do not work alone. Every segment or ICMP payload must be encapsulated within an IP datagram (or packet). |
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OSI Model: Presentation Layer
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provides a variety of coding and conversion functions that are applied to application layer data. ensure that information sent from the application layer of one system would be readable by the application layer of another system. Some examples of presentation layer coding and conversion schemes include common data representation formats, conversion of character representation formats, common data compression schemes, and common data encryption schemes. Think ASCII, JPEG, 3DES, etc...
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Define OSPF point to multipoint mode
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RFC standard.
Only allows automatic neighbor discovery if "pseudo-broadcasts" are enabled on links |
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10. Which of the following services use TCP? (Choose three.)
A. DHCP B. SMTP C. SNMP D. FTP E. HTTP F. TFTP |
B, D, E. SMTP, FTP, and HTTP use TCP.
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What is the Retransmit timer and its default setting?
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States the number of seconds to wait for an acknowledgment before retransmitting an LSA. Default 5 secs. Should always be bigger than transmit timer to avoid possibility of flapping.
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Define OSPF point to multipoint non broadcast mode
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Cisco Proprietary mode
only difference from RFC is that no automatic neighbor discovery is available |
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Which of the following services use UDP? (Choose three.)
A. DHCP B. SMTP C. SNMP D. FTP E. HTTP F. TFTP |
11. A, C, F. Explanation:DHCP, SNMP, and TFTP use UDP. SMTP, FTP, and HTTP use TCP.
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Define OSPF point to point mode
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Cisco Proprietary
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Application Layer (OSI)
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Interfaces between network and application software. Also includes authentication services.
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12. Which of the following are TCP/IP protocols used at the Application layer of the OSI model?
(Choose three.) A. IP B. TCP C. Telnet D. FTP E. TFTP |
C, D, E. Telnet, File Transfer Protocol (FTP), and Trivial FTP (TFTP) are all Application layer
protocols. IP is a Network layer protocol. Transmission Control Protocol (TCP) is a Transport layer protocol. |
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OSI Model: Application Layer
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interacts directly with user. Telnet, File Transfer Protocol (FTP), and Simple Mail Transfer Protocol (SMTP), HTTP. functions typically include identifying communication partners, determining resource availability, and synchronizing communication
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What is the metric for OSPF?
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100/Bandwidth in Mbps.
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If you use either Telnet or FTP, which is the highest layer you are using to transmit data?
A. Application B. Presentation C. Session D. Transport |
A. Both FTP and Telnet use TCP at the Transport layer; however, they both are Application
layer protocols, so the Application layer is the best answer for this question. |
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How do hello timers work and what are the defaults?
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OSPF sends out hellos at regular intervals to discover neighbors and to verify the neighbor list remains current. Neighbors time out after the dead time expires (by default 4 x hello time). Defaults are broadcast & point-to-point - 10 secs , non-broadcast & point-to-multipoint - 30 secs
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In what situation would you use an OSPF virtual link?
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In a situation in which an area can not be directly connected to area 0. As every area must connect to area 0, virtual links between the offending area's abr and the abr of the router between it and area 0 can be created to allow this other area to function.
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The DoD model (also called the TCP/IP stack) has four layers. Which layer of the DoD model
is equivalent to the Network layer of the OSI model? A. Application B. Host-to-Host C. Internet D. Network Access |
C. The four layers of the DoD model are Application/Process, Host-to-Host, Internet, and Network
Access. The Internet layer is equivalent to the Network layer of the OSI model. |
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Presentation Layer (OSI)
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Defines the format and organization of data. Includes encryption.
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Which two of the following are private IP addresses?
A. 12.0.0.1 B. 168.172.19.39 C. 172.20.14.36 D. 172.33.194.30 E. 192.168.24.43 |
C, E. Class A private address range is 10.0.0.0 through 10.255.255.255. Class B private
address range is 172.16.0.0 through 172.31.255.255, and Class C private address range is 192.168.0.0 through 192.168.255.255. |
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frame, packet, datagram, segment, message, cell
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frame - data link layer
packet - network layer datagram - network layer (connectionless) segment - transport layer message - application layer cell - data link layer for ATM & SMDS (contains 5 byte header & 48 byte payload |
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What layer in the TCP/IP stack is equivalent to the Transport layer of the OSI model?
A. Application B. Host-to-Host C. Internet D. Network Access |
B. The four layers of the TCP/IP stack (also called the DoD model) are Application/Process,
Host-to-Host, Internet, and Network Access. The Host-to-Host layer is equivalent to the Transport layer of the OSI model. |
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Whats the 6 LSA types?
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Type1 Router link=Generated by router & lists neighbors and costs, Type2 Network Link=Sent out by DR and lists all routers on the segment its adjacent too, Type3 Network Summary Link=ABRs generate to send between areas listing prefixes available in a given area, Type4 AS external ASBR Summary Link=ABRs produce to advertise ASBRs presence cost, Type5 External Link LSA=ASBR produces and floods throughout As advertising external routes, Type7 NSSA External LSA=Produced by ASBR, and is type 5 tunneled through the NSSA.
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Which statements are true regarding ICMP packets? (Choose two)
A. ICMP guarantees datagram delivery. B. ICMP can provide hosts with information about network problems. C. ICMP is encapsulated within IP datagrams. D. ICMP is encapsulated within UDP datagrams. |
B, C. ICMP is used for diagnostics and destination unreachable messages. ICMP is encapsulated
within IP datagrams, and because it is used for diagnostics, it will provide hosts with information about network problems. |
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Session Layer (OSI)
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Establishes and maintains end-to-end bidirectional flows between endpoints. Includes managing transaction flows.
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What is the address range of a Class B network address in binary?
A. 01xxxxxx B. 0xxxxxxx C. 10xxxxxx D. 110xxxxx |
C. The range of a Class B network address is 128–191. This makes our binary range
10xxxxxx. |
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Why are LSAs labeled with sequence numbers?
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So that older and newer versions of an advertisement can be distinguished and decide whether to update the current entry in the topology table.
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20. Which of the following protocols uses both TCP and UDP?
A. FTP B. SMTP C. Telnet D. DNS |
D. DNS uses TCP for zone exchanges between servers and UDP when a client is trying to
resolve a hostname to an IP address. |
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Transport Layer (OSI)
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Provides a variety of services between two host computers, including connection establishment and termination, flow control, error recovery, and segmentation of large data blocks into smaller parts for transmission.
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Process/Application Layer Protocols and programs.
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Telnet is a terminal emulation program
that allows you to log into a remote host and run programs. File Transfer Protocol (FTP) is a connection-oriented service that allows you to transfer files. Trivial FTP (TFTP) is a connectionless file transfer program. Simple Mail Transfer Protocol (SMTP) is a send-mail program. |
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What are the routing table LSA codes and there meanings?
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They show where the entry was generated from. O= 1.Router or 2.Network Link generated by the router or DR and propagated within an area, OIA=3 or 4 summary links generated by ABRs and propagated into backbone area and between ABRs, OE1 or OE2=5.Summary/external Link either E1 is internal + external cost or E2 only external cost.
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Host-to-Host layer protocols
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Transmission Control Protocol (TCP) is a
connection-oriented protocol that provides reliable network service by using acknowledgments and flow control. User Datagram Protocol (UDP) is a connectionless protocol that provides low overhead and is considered unreliable. |
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Network Layer (OSI)
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Logical addressing, routing, and path determination.
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Internet layer protocols.
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Internet layer protocols. Internet Protocol (IP) is a connectionless protocol
that provides network address and routing through an internetwork. Address Resolution Protocol (ARP) finds a hardware address from a known IP address. Reverse ARP (RARP) finds an IP address from a known hardware address. Internet Control Message Protocol (ICMP) provides diagnostics and destination unreachable messages. |
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What is the metric used by OSPF and how its calculated?
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It is the cost and is calculated by 1000,000,000bps/link speed. It is applied to the outgoing interface, and the routing process will select the lowest cumulative cost to a remote network.
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Class A range.
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The IP range for a Class A network is 1–126. This provides 8
bits of network addressing and 24 bits of host addressing by default. |
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Data Link Layer (OSI)
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Formats data into frames appropriate for transmission onto some physical medium. Defines rules for when the medium can be used. Defines means by which to recognize transmission errors.
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Class B range.
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The IP range for a Class B network is 128–191. Class B
addressing provides 16 bits of network addressing and 16 bits of host addressing by default. |
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Data Link Layer Addresses
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physical or hardware address. flat address space. pre-established and typically fixed relationship to a specific device
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Class C range.
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The IP range for a Class C network is 192–223. Class C
addressing provides 24 bits of network addressing and 8 bits of host addressing by default. |
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What are the 5 OSPF packet types?
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Hello=establishes communication with directly attached neighbors, Database Descriptor(DBD)=sends list of RIDs from whom the router has an LSA, Link-state Requests(LSR)=follow DBDs to ask for any missing LSAs, Link-state Update(LSU)=Replies to LSR with requested data, Link-state acknowledgement(LSAck)=Confirm receipt of link-state info
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Private IP ranges.
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Class A -> 10.0.0.0
through 10.255.255.255. Class B -> 172.16.0.0 through 172.31.255.255. Class C -> 192.168.0.0 through 192.168.255.255. |
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Physical layer (OSI)
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Defines the electrical, optical, cabling, connectors, and procedural details required for transmitting bits, represented as some form of energy passing over a physical medium.
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MAC Addresses
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type of data link layer address. used in LANs. Defined by IEEE MAC spec.48 bits as 12 hex digits. First 6 are Organizationally Unique Identifier (OUI) given by IEEE to vendor. Last 6 values administered by the specific vendor
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What IP protocol is OSPF traffic marked as?
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All OSPF traffic is transmitted inside IP packets marked as IP protocol 89
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Ethernet details
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Speed: 10 Mbps
Alternate Name: 10BASE-T Name of IEEE Standard: 802.3 Cable Type: Copper Max Length:100m |
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Address Resolution Protocol
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maps network addresses to MAC addresses. Hello protocol enables network devices to learn the MAC addresses of other network devices
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Fast Ethernet details:
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Speed: 100 Mbps
Alternate Name:100BASE-T Name of IEEE Standard:802.3u Cable Type: Copper Max Length: 100m |
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Why must the Backbone Area be at the centre of all other areas and physically connect to all other areas?
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Because OSPF expects all areas to inject routing info into the backbone, and in turn, the backbone will disseminate that info into other areas
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Gigabit Ethernet details:
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Speed: 1000 Mbp2
Alternate Name: 1000BASE-LX, 1000 BASE-SX Name of IEEE Standard: 802.3z Cable Type: Fiber Max Length: 550m (SX), 5 km (LX) |
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Network Layer Address
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hierarchical address space. called virtual or logical addresses. Each Network Interface Must Be Assigned a Network Address for Each Protocol Supported
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How many paths will OSPF load-balance with by default?
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Cisco routers will perform equal-cost load balancing for upto 4 paths, but this parameter can be increased by configuration up to as many as 16 paths.
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Gigabit Ethernet details:
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Speed: 1000 Mbps
Alternate Name: 1000BASE-T Name of IEEE Standard: 802.ab Cable Type:Copper Max Length: 100m |
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Flow Control
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a function that prevents network congestion by ensuring that transmitting devices do not overwhelm receiving devices with data. L4
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What should you do if a router configured for OSPF routing is not seeing an OSPF neighbor on an attached network?
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1.Make sure both routers are configured with same IP mask, MTU, Interface Hello timer, OSPF hello timer and OSPF dead interval, 2.Make sure both neighbors are in same area, 3.Use Debug and show cmds to trace the problem.
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three commonly used methods for handling network congestion
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buffering - temporarily store bursts of excess data in memory until they can be processed.
transmitting source-quench messages - receiving device sends source-quench messages to request that the source reduce its current rate of data transmission 1 message per dropped packet windowing - a flow-control scheme in which the source device requires an acknowledgment from the destination after a certain number of packets have been transmitted |
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What happens if there are routes with different routing information srcs to the same dst?
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The router will choose the path with the lowest AD. If both are OSPF, OSPF will select the lower type advertisements first, and choose lower costs to break ties.
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What are the benefits of summarization of IP subnets between areas?
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Reduces the size of the routing table, which in turn reduces CPU and memory requirements. It also speeds up convergence. The greater the summarization, the smaller and fewer the LSA packets that need to be propagated
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What are the 2 types of summarization that exist in OSPF?
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Interarea summarization is performed at the ABR, and creates Type 3 and Type 4 LSAs. These routes are sent between areas. External summarization is performed at the ASBR, and creates Type 5 LSAs. These routes are sent into OSPF from another routing protocol.
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How does a ABR forward summary LSAs?
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It forwards Type 3 LSAs to other ABRs and Type 4 LSAs to the ASBRs. It also forwards Type 3 LSAs from other areas into its own area. If the ABR has multiple links in the same area, it also forwards Type 1 and 2 LSAs in its capacity as an internal router.
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What are external routes and how are there costs calculated?
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They are routes that didn't originate in the OSPF domain and have been redistributed from another routing protocol (routing domain) or static routing. An external route is introduced into the OSPF domain by an ASBR. External routes discovered by OSPF can have there paths calculated in 1 of 2 ways. E1=cost of path to ABR is added to external cost to reach next hop router outside the AS, E2=External cost of path from ASBR. E2 is default, but E1 is preferred over E2 if 2 equal-cost paths exist.
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What happens if OSPF identifies a problem or a link goes down?
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As soon as OSPF identifies a problem it modifies its LSAs accordingly and sends updated OSPFs to the remaining neighbors with full adjacency. Being event driven, this improves convergence times.
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When should a DR be manually selected using priorities?
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In a partial mesh network (eg hub-and-spoke), and the chosen DR should be a router with permanent virtual circuits (PVCs) connecting to all other routers. The DR idea doesn’t work well in a partial mesh because the elected router may not be able to reach all other routers.
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What type of networks don’t involve a DR/BDR election?
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Point-to-multipoint and point-to-point network types, only the non-Broadcast and Broadcast network types have the DR/BDR election.
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Which network types offer neighbor recognition?
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Non broadcast OSPF networks like NBMA cant dynamically discover there neighbors, so the neighbors must be manually identified. However Broadcast networks like point-to-point can.
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What OSPF network types are available on Cisco router interfaces?
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Broadcast Multiaccess, Point-to-Point, Point-to-Multipoint (default is Point-to-Multipoint broadcast, but nonbroadcast is available), and Nonbroadcast Multiaccess (NBMA)
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Broadcasts and multicasts aren't supported on which OSPF network type?
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NBMA is used to accurately model X.25 and frame relay environments in multiple-access networks where there are no intrinsic broadcast and multicast capabilities. In an NBMA configuration, OSPF sends HELLO packets to each router one at a time rather than multicasting them. The HELLO timer is extended from 10 to 30 secs and dead router timer from 40 to 120 secs.
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What steps need to be performed to configure a router to support OSPF in a non-broadcast environment with the NBMA OSPF network type?
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Because NBMA is the default OSPF network type, its only really necessary to identify neighbors.
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Which network types are best applied to full-mesh topologies?
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Multiaccess topologies, such as those found in NBMA and broadcast OSPF network types, rely on DRs and so are best applied to full mesh-topologies. The only real difference is that Broadcast network types are capable of discovering there neighbors automatically. Ethernet links are automatically recognized as broadcast links.
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Which OSPF network types are Cisco proprietary, and which are RFC compliant?
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Non-broadcast and point-to-multipoint (broadcast) are RFC Complaint, whilst point-to-multipoint (non-broadcast), broadcast and point-to-point are Cisco proprietary
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What is the default OSPF network type for a physical serial interface?
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Non-broadcast Multiaccess. Multipoint subinterfaces are also treated like other interfaces, so their default OSPF network type is also NBMA. Multipoint interfaces on Cisco routers automatically start in non-broadcast mode. Point-to-point subinterfaces are treated by the router exactly as if they were point-to-point circuits. These interfaces automatically use the point-to-point OSPF network type.
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Whats a stub area?
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Is an area that wont except external routes (Type 5). They are replaced by a default route, and internal routers send external traffic to the closest ABR. Useful to protect slowest or less powerful routers from being overwhelmed with routes from outside. An area that has a single ABR or an ABR where the choice of exit ABR is not important is a good candidate for a stub area.
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Whats a totally stubby area?
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An area that doesn’t accept summary LSAs from other areas (Type 3 & 4) or external summary LSAs (Type 5). Protects internal routers by minimizing routing tables and summarizing everything outside the area with a default route. Is Cisco proprietary.
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Whats a Not-So-Stubby-Area (NSSA)?
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Are stubby areas that can have ASBRs. Since stubby areas don’t support Type 5 LSAs, they use Type 7 LSAs to disguise external information and the ABR converts the Type 7 to Type 5 when its sent to Area 0. Can also have Not-so-totally-stubby areas. NSSA external routes show up as N1 or N2 instead of E1 or E2 in the routing table. Note the ABR so a NSSA doesn't automatically generate a default route.
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What certain characteristics unite all stub area types?
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Area 0 can`t be a stub, all routers in the area must agree that its a stub area, and no virtual links may traverse a stub area.
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What is a disadvantage of stub areas?
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Routers in a stub area will always route external traffic through the closest ABR. Sometimes this can cause inefficient routing if there is a better path.
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Frame Relay
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An International standard data-link protocol that defines the capabilities to create a frame-switched (packet-switched) service, allowing DTE devices (typically routers) to send data to many other devices using a single physical connection to the Frame Relay service.
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HDLC
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High-Level Data Link Control. A bit-oriented synchronous data link layer protocol developed by the International Organization Standardization (ISO).
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PPP
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Point-to-Point Protocol. A protocol that provides router-to-router and host-to-network connections over synchronous point-to-point and asynchronous point-to-point circuits.
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Size of A Network
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1 Byte of Network Bytes
3 Bytes of Host Bytes 2^24 -2 of Addresses per network |
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Size of B Network
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2 Bytes of Network Bytes
2 Bytes of Host Bytes 2^16 -2 of Addresses per network |
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Seize of C Network
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3 Bytes of Network Bytes
1 Byte of Host Bytes 2^24 - 2 of Addresses per network |
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Class A - Valid Network Range
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1 to 126
1.0.0.0 to 126.0.0.0 126 Possible Networks 16,777,214 Possible Hosts |
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Class B - Valid Network Range
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128 to 191
128.0.0.0 to 191.255.0.0 16,384 Possible Networks 65,534 Possible Hosts |
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Class C - Valid Network Range
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192 to 223
192.0.0.0 - 223.255.255.0 2,097,152 Possible Networks 254 Possible Hosts |
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TCP/IP Transport Layer Feature - Multiplexing using ports
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Function that allows receiving hosts to choose the correct application for which the data is destined, based on the port number
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TCP/IP Transport Layer Feature - Error recovery
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Process of numbering and acknowledging data with Sequence and Acknowledgement header fields.
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TCP/IP Transport Layer Feature - Flow control using windowing
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Process that uses window sizes to protect buffer space and routing devices.
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TCP/IP Transport Layer Feature - Connection establishment and termination
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Process used to initialize port numbers and Sequence and Acknowledgment fields.
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TCP/IP Transport Layer Feature - Ordered data transfer and data segmentation
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Continuous stream of bytes from an upper-layer process that is "segment" for transmission and delivered to upper-layer processes at the receiving device, with the bytes in the same order.
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sliding windows
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For protocols such as TCP that allow the receiving device to dictate the amount of data the sender can send before receiving an acknowledgment-- a concept called a window--a reference to the fact that the mechanism to gran future windows is typically jsut a number that grows upwards slowly after each acknowledgment, sliding upward.
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Switching Method - Store and forward
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The switch fully receive all bits in the frame (store) before forwarding the fram (forward). This allows the switch to check the FCS before forwarding the frame.
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Cut-through
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The switch forwards the frame as soon as it can. This reduces latency but does not allow the switch to discard frames that fail the FCS check.
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Interior Gateway Protocol
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A routing protocol that was designed and intended for use inside a single autonomous system.
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Exterior Gateway Protocol
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A routing protocol that was designed and intended for use between different autonomous system.
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Distance Vectors
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RIP-1, RIP-2, IGRP
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Link-state
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OSPF, Integrated IS-IS
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Balanced hybrid (also called advanced distance vector)
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EIGRP
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Classless vs Classful routing protocols
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Classless - Supports VLSM, Sends subnet mask in routing updates, Supports manual route summarization.
Classful supports none of these. |
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ATM
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Asynchronous Transfer Mode. The international standard for cell relay in which multiple service types (such as voice, video, and data) are conveyed in fixed-length (53-byte) cells. Fixed-length cells allows cell processing to occur in hardware, thereby reducing transit delays.
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