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79 Cards in this Set

  • Front
  • Back
What is Routing?
The process of forwarding packets (layer 3 PDUs).
Define logical addressing:
Addresses that can be used regardless of the type of physical networks used, providing each device (at least) one address. Logical addressing enables the routing process to identify a packet’s source and destination.
What is a Routing Protocol?
A protocol that aids routers by dynamically learning
about the groups of addresses in the network, which in turn allows the routing (forwarding) process to work well.
Name four network layer TCP/IP utilities
DNS, DHCP, ARP, and ping
Explain two meanings of "Path Selection"
Sometimes it's used to mean the same thing as routing protocol, sometimes it's used to refer to the routing (forwarding) of packets, and sometimes is used for both functions.
Why is IP a connectionless protocol?
It does not require any overhead agreements or messages before sending a packet.
IP tries to deliver each packet, but if a router or host’s IP process cannot deliver the packet, it __________.
is discarded with no error recovery.
Which transport layer protocol provides error recovery and resending lost data.
TCP
When reading a packet, the router:
Compares the destination network layer address in the packet to the entries in the routing table and makes a match
That is forwarded in the routing process?
The packet, and only the packet, end to end through the network, discarding data link headers and trailers along the way.
Because routers build new data link headers and trailers, and because the new headers contain data link addresses, the PCs and routers must have:
Some way to decide what data link addresses to use (Example - ARP).
What are the two main concepts of routing?
1. The process of routing forwards Layer 3 packets, also called Layer 3 protocol data units, based on the destination layer 3 address in the packet.

2. The routing process uses the data link layer to encapsulate the Layer 3 packets into Layer 2 frames for transmission across each successive data link.
LEARN THE IPv4 HEADER!
LEARN THE IPv4 HEADER!
What is TTL?
(TTL) Time to Live - An IPv4 header value used to prevent routing loops.
What is the difference between a "Routing Protocol" and a "Routed Protocol"?
- A routing protocol learns routes and puts those routes in a routing table.

- A routed protocol defines the type of packet forwarded, or routed, through a network.
In regards to IP addressing, what must not be separated by a router?
All IP addresses in the same subnet
What must be in different subnets?
IP addresses separated by a router
Talk about IANA and ICANN
The Internet Assigned Numbers Authority (IANA) formerly owned the IP address assignment process. ICANN, in turn, assigns regional authority to other cooperating organizations.
What is the Class A IP range?
1 to 126
What is the Class B IP range?
128 to 191
What is the Class C IP range?
192 to 223
What is the Class D IP range?

What is this range used for?
224 to 239

Reserved for Multicast groups
What is the detailed Class A range?
1.0.0.1 to 126.255.255.254
Why is 127.x.x.x left out of the Classful addressing scheme?
127 can't be used for binary purposes (something about making all ones and/or zeroes addresses), so it is reserved for loopback or localhost testing.
What is the word Subnet short for?
Subdivided Network
How many networks and hosts are supported on Class A networks?
16 million hosts on each of the 127 networks
How many networks and hosts are supported on Class B networks?
65,000 hosts on each of the 16,000 networks
How many networks and hosts are supported on Class C networks?
254 hosts on each of the 2 million networks
All Cisco routers are classful routers, meaning:
They expect a default subnet mask on each interface of the router.
When using default routing, you must:
you must use the ip classless command because it’s possible that no remote subnets will be in the routing table.
Do classful routing protocols support the advertisement of subnet information?
Nope, you can only advertise subnet information (VLSM) with Classless routing protocols such as RIPv2, EIGRP, and OSPF.
What is the two step routing logic of a HOST?
1. If the destination IP address is in the same subnet as I am, send the
packet directly to that host.

2. If the destination IP address is not in the same subnet as I am, send the packet to my default gateway.
What is the four step routing logic of a ROUTER receiving a data-link frame with an encapuslated IP packet?
1. Use the data link FCS field to ensure that the frame had no errors; if errors occurred, discard the frame.

2. Assuming the frame was not discarded at step 1, discard the old data link header and trailer, leaving the IP packet.

3. Compare the IP packet’s destination IP address to the routing table, and find a route that matches the destination address. This route identifies the outgoing interface of the router, and possibly the next hop router.

4. Encapsulate the IP packet inside a new data link header and trailer,
appropriate for the outgoing interface, and forward the frame.
What is the class A private network? How many networks?
10.0.0.0

1 network
What are the class B private networks? How many networks?
172.16.0.0 to 172.31.0.0

16 networks
What are the class C private networks? How many networks?
192.168.0.0 to 192.168.255.0

256 networks
How many bits in an IPv4 address? Octets?
32 bits, 4 octets
Go through the multi-step routing process, end to end until committed to memory!
Go through the multi-step routing process, end to end until committed to memory!
Size of network and host parts (in bits and bytes) in a class A address?
8 bits network, 24 bits host

1 byte network, 3 bytes host
Size of network and host parts (in bits and bytes) in a class B address?
16 bits network, 16 bits host

2 byte network, 2 bytes host
Size of network and host parts (in bits and bytes) in a class C address?
24 bits network, 8 bits host

3 byte network, 1 bytes host
What is the standard IP address format called?
Dotted Decimal format
/25

1. Mask
2. Block Size
3. Hosts
4. Wildcard
5. How many bits on and off?
/25

.128 Mask
Block Size of 128
126 Hosts
Wildcard Mask of .127
1 bit on, 7 bits off
/26

1. Mask
2. Block Size
3. Hosts
4. Wildcard
5. How many bits on and off?
/26

.192 Mask
Block Size of 64
62 Hosts
Wildcard Mask of .63
2 bits on, 6 bits off
/27

1. Mask
2. Block Size
3. Hosts
4. Wildcard
5. How many bits on and off?
/27

.224 Mask
Block Size of 32
30 Hosts
Wildcard Mask of .31
3 bits on, 5 bits off
/28

1. Mask
2. Block Size
3. Hosts
4. Wildcard
5. How many bits on and off?
/28

.240 Mask
Block Size of 16
14 Hosts
Wildcard Mask of .15
4 bits on, 4 bits off
/29

1. Mask
2. Block Size
3. Hosts
4. Wildcard
5. How many bits on and off?
/29

.248 Mask
Block Size of 8
6 Hosts
Wildcard Mask of .7
5 bits on, 3 bits off
/30

1. Mask
2. Block Size
3. Hosts
4. Wildcard
5. How many bits on and off?
/30

.252 Mask
Block Size of 4
2 Hosts
Wildcard Mask of .3
6 bits on, 2 bits off
/31

1. Mask
2. Hosts
3. How many bits on and off?
4. Significance?
/31

.254 Mask
2 Hosts
7 bits on, 1 bits off
ONLY USED FOR POINT-TO-POINT LINKS
To subnet a class B, add ___ to the CIDR notation. For class C, add ____.
Add 8 for class B, add 16 for class C.
2^1

through

2^15
2^1 - 2 2^2 - 4 2^3 - 8 2^4 - 16
2^5 - 32 2^6 - 64 2^7 - 128
2^8 - 256 2^9 - 512 2^10 - 1,024
2^11 - 2,048 2^12 - 4,096 2^13 - 8,192
2^14 - 16,384 2^15 - 32,768
How do you calculate the number of subnets?
2^Masked bits (1's)
How do you calculate the number of hosts per subnet?
2^Host bits - 2

Host bits being 0's
/24

What is the significance?
1. Mask
2. Block Size
3. Hosts
4. Wildcard
5. How many bits on and off?
/24

Default Class C Network
.0 Mask (255.255.255.0)
Block Size of 1
254 Hosts
Wildcard Mask of 0.0.0.255
0 bits on, 8 bits off
/20

1. Mask
2. Block Size
3. Hosts
4. Wildcard
5. How many bits on and off?
/20

.240.0 Mask
Block Size of 16
4,096 Hosts
Wildcard Mask of .15.255
4 bits on, 12 bits off
/16

What is the significance?
1. Mask
2. Block Size
3. Hosts
4. Wildcard
5. How many bits on and off?
/16

Default Class B Network
.0.0 Mask (255.255.0.0)
Block Size of 1
2^16 Hosts (Appx. 65,000)
Wildcard Mask of 0.0.255.255
0 bits on, 16 bits off
/8

What is the significance?
1. Mask
2. Block Size
3. Hosts
4. Wildcard
5. How many bits on and off?
/8

Default Class A Network
0.0.0 Mask (255.0.0.0)
Block Size of 1
2^24 Hosts (Approx. 16 million)
Wildcard Mask of 0.255.255.255
0 bits on, 24 bits off
What is /32
255.255.255.255

Broadcast Address
What are the leading bits in a binary class A address?
0
What are the leading bits in a binary class B address?
10
What are the leading bits in a binary class C address?
110
/12

1. Mask
2. Block Size
3. Hosts
4. Wildcard
5. How many bits on and off?
/12

.240.0.0 Mask
Block Size of 16
2620 (Approx. 1 million) Hosts
Wildcard Mask of 0.15.255.255
4 bits on, 20 bits off
What is the CIDR notation range?
/8 to /32
The routing (forwarding) process depends heavily on:
having an accurate and up to date IP routing table one ach router.
Define Convergence Time
The time between losing the route and finding a working route.
Name six goals of routing protocols:
1. To dynamically learn and fill the routing table with a route to all subnets in the network.
2. If more than one route to a subnet is available, to place the best route in
the routing table.
3. To notice when routes in the table are no longer valid, and to remove them from the routing table.
4. If a route is removed from the routing table and another route through another neighboring router is available, to add the route to the routing table.
5. To add new routes, or to replace lost routes, with the best currently
available route as quickly as possible. The time between losing the route and finding a working route is called convergence time.
6. To prevent routing loops.
What are the general steps routing protocols follow for advertising routes in a network?
Each router adds a route to its routing table for each subnet directly connected to the router.
2. Each router tells its neighbors about all the routes in its routing table, including the directly connected routes and routes learned from other routers.
3. After learning a new route from a neighbor, the router adds a route to its
routing table, with the next hop router typically being the neighbor from which the route was learned.
These are four tools used almost every day in almost every TCP/IP network in the world to help the network layer with its task of routing packets from end to end through an internetwork:
1. Address Resolution Protocol (ARP)
2. Domain Name System (DNS)
3. Dynamic Host Configuration Protocol (DHCP)
4. Ping
If two devices are on two separate networks and one device needs to know the
MAC address of another device, it ______.
It forwards the packet to its default gateway
Discuss the term ARP cache
Any device that uses IP should retain, or cache, the information learned with ARP, placing the information in its ARP cache. Hosts only need to use ARP to find MAC addresses once in awhile.
Each time a host needs to send a packet encapsulated in an Ethernet frame, it first
it first checks its ARP cache and uses the MAC address found there.
If the correct information is not listed in the ARP cache, a host
uses ARP to discover the MAC address used by a particular IP address.
Hosts can learn each other’s ____ when they exchange MAC information via
ARP.
MAC address
What is the DHCP process?
1. DHCP Discover Message (LAN Broadcast)
2. DHCP Offer Message Directed to Client
3. DHCP Request Message Directed to Server
4. DHCP Acknowledgement Directed to Client
"Ping" stand for:
Packet Internet Groper
What protocol does ping use?
ICMP
What does ICMP stand for?
Internet Control Message
Protocol
Talk about ICMP
ICMP is an integral part of IP, used for error reporting and relaying messages... not for carrying data.
What do the following CISCO ping messages mean?

! (exclamation mark)
. (period)
U | (vertical bar)
? C & (ampersand)
! = Success . (period) = Timed out waiting for reply
U = Destination unreachable
| (vertical bar) = Ping process interrupted
? = Unknown packet type C = Congestion experienced
& (ampersand) = Time to live exceeded