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262 Cards in this Set

  • Front
  • Back

What is the EIGRP Topology Table?

A table used by each EIGRP router containing all routes to all destinations (even redundant ones). These routes are known as "feasible successors"

What is a successor route and what protocol is it associated with?

In EIGRP, a successor route is chosen from the many feasible routes on a router that traffic can take to a destination based on its feasible distance. The route with the lowest feasible distance metric is used.

What is exchanged when an EIGRP router is first powered on?

Hello packets followed by topology tables.

How often are hello packets exchanged in EIGRP?

< / = T1 - Every 30 seconds

> T1 - Every 5 seconds

How long is EIGRP hold time?

3 times the hello interval without the exchange of hellos.

What is Proxy ARP?

Proxy Address Resolution Protocol is present on all routers. When packets leave a LAN, the gateway router responds to a sending host with its own MAC address and once it begins to receive the host's packets it routes them to the destination on its behalf.

What is a Layer 3 Broadcast Domain commonly referred to as?

A LAN or Local Area Network.

What is a feasible successor?

A route to a given destination for a router using EIGRP that is not the most efficient path and is stored in the topology table. Feasible successors are available in the event that a successor route fails.

Which command is used to view the EIGRP topology table?

show ip eigrp topology

What is the difference between EIGRP feasible distance and EIGRP reported distance?

A router's neighbors will report their own distances from a network to the router using administrative distances, this is known as the reported distance. A router's own distance from the same network using metrics is known as the feasible distance.

What is advertised distance?

An alternate term used for EIGRP reported distance.

What is the EIGRP feasibility condition?

If a neighboring router's reported distance is greater than the local router's own feasible distance, the reported route will not be stored in the routing table. This is to prevent loops.

What is the primary purpose of Layer 3?

The Network Layer controls communication between broadcast domains and among devices not connected directly.

How do broadcasts and multicasts differ?

Multicast : Broadcast :: Subscription : Junkmail

A broadcast reaches all network devices regardless of whether it is intended for all or not. A multicast reaches only certain "subscribers" within a network.

IPv6 cannot send what type of commonly used IPv4 message?


What is considered best practice when assigning IP addresses to devices in a PPP network?

Given that a PPP network is a link between only 2 devices, a subnet mask of (or /30) is best used leaving 4 addresses total and only two assignable IP addresses.

What happens when one host pings another?

1. Internet Control Messaging Protocol (ICMP) sends an ARP request to the broadcast address of to determine the MAC address of the queried host given the IP address.

2. The queried host sends a replies with its MAC address which the originating host stores in its MAC address table. After this ARP will not need to be performed again

Given a subnet mask, how would the number of subnets, hosts, and hosts per network be calculated?

Subnets: 2^(borrowed bits)

Hosts: 2^(host bits - 2)

Hosts per network: Hosts/ subnets

*It is important to remember that borrowed bits change based on which class the address would have been

What is EIGRP Variance?

EIGRP Variance allows for the use of feasible routes that would otherwise not be used. Variance is a user defined value whose default is 1 that multiplies the successor route's metric and chooses any feasible routes lower than the product of the successor and variance for equal cost load sharing.

What is the purpose of EIGRP Manual summarization?

Summarizes multiple subnets as a single network with a modified subnet mask based on the last bit that all the network addresses have in common.

What is OSPF?

Open Shortest Path First is a link state routing protocol. Each router that joins the network summarizes itself through Link State Advertisements (LSAs) . Every router stores the information in an identical Link State database and each individually performs the Dijkstra algorithm on the database to calculate its routes.

What information do router LSAs contain?

Links/ Interfaces

Connected Networks

Neighboring routers and their distances

What is Router on a Stick?

A silly name for what is basically inter-VLAN routing. A single trunk connection can be created between a switch with multiple VLANs and a router using virtual sub interfaces on the router's physical interface each with its own IP address for each VLAN. The sub interfaces share the same MAC address.

What is an adjacency?

In OSPF, adjacencies are neighboring routers and are contained in a neighbor table.

What constitutes an adjacency?

In OSPF, routers are considered neighbors if they have matching:

- IPs/ subnets

- Authentication

- Hello timers

- Area IDs

By default, an OSPF dead timer is ___ times the hello interval.


How does an OSPF router pick its ID?

1. Router will use manually configured ID if present (IDs are in IPv4 format)

2. If no ID is manually configured, the highest loopback IP is chosen

3. If no loopback is present, the router will choose the highest physical interface's IP

What is administrative distance? List all 7 covered by the CCNA exam.

1. Connected directly = 0

2. Static Route = 0 (exit interface) 1 (next hop IP)

3. EBGP = 20

4. EIGRP = 90

5. OSPF = 110

6. RIP and RIPv2 = 120

7. IBGP = 200

If a route is not static, it's either a _____ or a ______. Describe the difference.

Distance Vector Route or a Link State Route

DV sends its neighbors a list of all known networks and its distance from these networks.

LS describes itself and its directly connected objects so that info is passed from one router to another and the entire network topology down to each connection is known.

What is RIP?

Routing Information Protocol is a distance vector routing protocol that broadcasts the entire contents of its routing table to directly connected devices every 30 seconds. This is generally inefficient using unnecessary bandwidth and is prone to routing loops when routers are unaware of topology changes.

What is a DR?

In OSPF multi access networks, a Designated Router is chosen. This router becomes the only adjacency to all other routers. This eliminates a network clogged with LSAs when many routers are present

How is a DR or Backup DR chosen?

First by OSPF priority number, this is usually 1 by default. If all priority numbers are 1, the router with the highest ID is chosen.

How are LSAs relayed in an OSPF multi access network?

Multicast for backup DRs by DR.

Multicast to all other routers by DR.

What is the difference between DTE and DCE

Data Terminating Equipment typically includes standrad router interfaces

Data Connection Equipment is a device that provides clocking on a link. A serial cable has a DCE and DTE end, whichever router is on the DCE end must be set with a clock rate.

What is clocking?

The physical bit transfer rate between two routers.

What encapsulation do serial connections use?

High Level Data Link Layer Control also known as HDLC. They can also use the open PPP standard.

What 7 fields are contained in OSPF hello packets?

1. Router ID

2. Router IDs of neighbors

3. Hello/ dead timers

4. Router's OSPF Priority

5. Area ID of originating interface

6. DR IP address (and backup)

7. Authentication information

8 Steps of the LSDB exchange in OSPF:

1. Down

2. Attempt


4. 2way

5. Exstart

6. Exchange

7. Loading

8. Full

5 LSA Types:

1. Router LSA

2. Network LSA - sent by DR, describes network using IP address and all connected routes

3. Network Summary LSA - sent by ABRs and exchanged with opposite network. Sums both bordering networks

4. ASBR LSA - ASBR makes location known - relayed by ABRs

5. External LSA - Selected networks on WAN are imported by ASBR

What are the three types of OSPF area routers?

1. ABR - Area Border Routers are routers that border two areas

2. ABSR - Autonomous System Boundary Routers connect a WAN to the internet

3. AIR - Area Internal Routers exist only within one area

What command can be used to bring up a PC's ARP table?


What are RIP's loop prevention mechanisms?

1. Max Hop Counts

2. Split Horizon - updates about a specific network cannot be sent/ received simultaneously

3. Route Poisoning - down links have an infinite hop count

4. Route Invalid Timer - after 3 minutes without advertisement a route goes into hold down

5. Hold Down Timer - Updates will not be accepted about route for a specific amount of time

6. Poison Reverse - nearest links are advertised of links in hold down

7. Flush Time - route is completely removed after 2 mins in hold down

What is EIGRP?

Enhanced Interior Gateway Protocol is a Cisco proprietary distance vector (sometimes referred to as hybrid) It sends non periodic and partial updates only pertaining to topology.

Practice subnetting at:


What is a CSU/ DSU?

The point of demarcation between a customer's gateway and an ISP's equipment. This is typically a serial connection.

What is the primary purpose of Layer 4?

The Transport Layer controls communication between devices.

What PDU is found at Layer 4?

The segment.

What are the three ranges of TCP/ UDP ports?

Well Known Ports: 1 - 1023

Registered Ports: 1024 - 49,151

Ephemeral/ Open Ports - 49,152 - 65,535

What rule of thumb should be used when creating ACLs?

Standard ACLs are applied closest to the destination while Extended ACLs are applied closest to the source. Furthermore, more specific statements should be made first followed by more general statements.

What is an ACL?

Access Control Lists control traffic through or to a router.

What type of ACLs are there?

Standard - permits/ denies traffic based only on source IP address and can be assigned 1 - 99 in IOS

Extended - permits/ denies traffic based on both source and destination IP addresses as well as port number or service and can be assigned 100 - 199 in IOS

What is RSTP?

Rapid Spanning Tree Protocol is IEEE 802.1w and reduces spanning tree's 50 second start up process to 4 - 6 seconds. Unlike STP, RSTP is not timer based and uses BPDUs to decide which switch is superior using the same criteria as STP.

What are the four states of RSTP?

1. Discarding

2. Discarding

3. Learning

4. Forwarding

What are the private IP address ranges?

Class A: -

Class B: -

Class C: -

What is PAT?

Port Address Translation (aka NAT with overload) is a method of allowing end devices using the same public IP to be differentiated by their default gateway by assigning them each their own Layer 4 port.

What is the purpose of Static NAT?

Static NAT assigns an internal device a specific public IP for for ease of external connection. This is typically used for servers.

Why might PPP be used in place of HDLC?

HDLC standards are vendor proprietary, and multiple devices of different makes will be unable to communicate. PPP is an open standard and universally understood by all devices.

What is PPP?

Point to Point Protocol is a Layer 2 encapsulation method. It can be used in place of HDLC.

What are some of the other advantages PPP has in addition to scalability ?

Authentication - verifies end devices are not malicious using PAP and CHAP.

Compression - reduces data size saving bandwidth

PPP Multi-link - allows for multiple side by side physical links to become a single logical link

)ex: Three 1mbps links become single 3mbps link

How do PAP and CHAP differ? Why are they significant?

Password Authentication Protocol uses plain text while Challenge Handshake Authentication Protocol uses encryption.

Both of these protocols are a type of PPP sub protocol called Link Control Protocol (LCP) which initializes a PPP link.

How are ports opened?

Ports are opened using a three way handshake:

1. Host 1 sends a segment with the sync bit turned on to Host 2

2. Host 2 replies with a SYNC Acknowledgement

3. Host 1 replies to Host 2's SYNC ACK w/ an ACK

What does NCP do?

Network Control Protocol is a PPP sub protocol that negotiates Layer 3 protocols. Today IPCP (Internet Protocol Control Protocol) is the only protocol used for the most part, however in the past, NCP could adopt protocols such as AppleTalk and IPX.

What does window size describe?

The number of segments that can be sent during transit without an ACK required. This value is 1 by default.

What is a peer neighbor route?

This is a direct route with a /32 mask installed by PPP to the routing table. This enables communication between two interfaces on different subnets. Without this feature, traversal between subnets on Layer 3 wouldn't be possible.

What is CDP?

Cisco Discovery Protocol is a Cisco protocol that allows for a network of Cisco devices to mapped out. CDP is enabled by default, but as it can pose a potential security threat in certain situations it might be best to disable it using the command "no cdp run".

What are the three Layer 2 encapsulation types?

1. High Level Data Link Control (HDLC)

2. Point to Point Protocol (PPP)

3. Frame Relay

What is an NBMA?

Non-Broadcast Multi-Access technology cannot send broadcasts in contrast to Ethernet which is considered Broadcast Multi-Access and has a broadcast address of all F's.

What is Frame Relay?

A Layer 2 encapsulation type as well as an NBMA technology. Frame Relay is often used in connecting remote sites through an ISP's network in a hub/ spoke formation and uses packet switching.

What is MPLS?

Multi-Protocol Label Switching is a data carrying protocol that is considered to reside between Layers 2 and 3 and utilizes packet switching. It can often be used in place of Frame Relay and provides the added benefits of QoS , lower overhead, and VPN capability among other things.

What is a PVC?

A Permanent Virtual Circuit is a connection between 2 remote sites through an ISP cloud often seen in Frame Relay and is permanently available as opposed to a switched virtual circuit which is established on demand but not maintained.

What is an Access Link and an Access Rate?

These terms are used by an ISP to describe the connection to their network provided to a customer and the speed of that link respectively.

What is CIR and CBIR?

A Committed Information Rate is the bandwidth negotiated between a customer and an ISP for a PVC. The Committed Burst Information Rate is allotted extra speed and allows for more data to travel at once if other connected PVCs are not being used as heavily.

For each Layer 3 hop through the internet, which address will be changed?

The source/ destination MAC address.

What is a hub/ spoke formation?

A method of connecting remote sites through PVCs connected to a central logical location. The hub's router routes traffic between these sites minimizing the requirement for each of the sites to be interconnected through their own individual PVCs.

What is a DLCI?

A Data Link Connection Identifier is an identifying number provided by an ISP that can be used in configuration to reach a remote site through a PVC. This can be considered the MAC address of Frame Relay and these numbers change with each hop through the ISP's network.

What are LMIs?

Local Management Interfaces are used in Frame Relay to announce all DLCIs to a router. These are similar hellos to keep a link alive. LMIs will stop displaying DLCIs for a link that goes down.

What are the three types of LMIs?




What are the two types of Frame Relay encapsulation found in Cisco IOS?

Default (Cisco proprietary)

IETF (open standard)

What is Inverse ARP?

Similar to regular ARP in ethernet, Inverse ARP seeks to resolve a remote router's IP address given its DLCI. This is the inverse of ARP which searches for a MAC given an IP. Inverse ARP will only work if both ends have been configured with an IP address.

How many bits do IPv6 addresses have?

128 bits written in 8 hexadecimal fields of 16 bits each. Each character in an address represents four bits (also known as a nibble).

How would an IPv6 network address be written?

Network addresses are 128 bits and written in hex groups but end in a double colon signifying trailing 0s representing host bits. Subnets are always notated with a slash.

What are the four steps of the EUI-64 configuration process?

1. The host's 48 bit MAC address is split down the middle

2. 16 bits - FFFE - are placed between the first (OUI) and second 24 bits.

3. The UL bit is turned on to reflect this change.

4. The 64 bit network address and newly created 64 bit host address are combined to create an IPv6 address

What is the UL?

The Universal Local bit is the 7th bit of a 48 bit MAC address that is always turned off unless the MAC address is modified. The decimal value of this bit is 2 which modifies the representing hex character's value. This bit may be turned on after EUI-64 or if the MAC is manually modified for any reason.

What is stateless configuration mode?

A mode that can be enabled for EUI-64 which automates the process.

What are the 5 steps of the router boot sequence?

1. Router is powered on

2. Router performs POST (Power On Self Test)

3. Bootstrap program (stored in ROM) searches for OS (stored in flash) and loads it

4. IOS is expanded to RAM

5. startup-config is retrieved from NV-RAM or a TFTP server and loaded into RAM as running-config

What happens when a Cisco device is powered on without a startup-config file?

The device opens the configuration dialogue.

What is NDP?

Neighbor Discovery Protocol serves a very similar purpose to ARP in an IPv6 network and resolves MAC addresses give an IP addresses using ICMPv6 (as opposed to ICMPv4) And also confirms that IP address conflicts with other hosts do not exist.

How does ICMPv6 query MAC addresses?

All nodes on the same data link join the multicast address FF02: 4 groups of zeros :1:FF which totals only 104 bits. The remaining 24 are filled by last 24 bits of the queried host's IP to total 128 bits.

How does ICMPv6 query MAC addresses?

All nodes on the same data link join the multicast address FF02: 4 groups of zeros :1:FF which totals only 104 bits. The remaining 24 are filled by the last 24 bits of the queried host's IP to total 128 bits.

What is STP's IEEE designation?


How does HSRP work?

One router out of the group is designated as the Active Router, leaving the remaining routers in standby in the event that the active router goes down. Routers in an HSRP group maintain hello packets.

What is the HSRP hello interval? What is active time?

HSRP routers exchange hellos every 3 seconds with a hold time of 10 seconds. Active time is also maintained between hellos and is reset each time a new hello is received.

How is a virtual MAC address created in HSRP?

The first 24 bits of the MAC address are the standard OU. The next 16 bits are always 07:AC which is exclusive to HSRP. The final 8 bit group represents the HSRP group number.

How is the active router determined in an HSRP group?

Routers in the group are configured with a standby priority ranging from 1 to 255. The router with the highest value becomes the active router and the next highest values determine the active router's successors.

What is interface tracking?

In HSRP, interface tracking can be enabled to decrease the active router's priority by 10 should its ISP link fail. The next router in line then succeeds as the active router. If the original active router regains its connection, its priority is restored and it becomes active once again. This feature ensures the virtual router always maintains connectivity.

What is GLBP?

Gateway Load Balancing Protocol is similar to HSRP in many ways but allows for the load to be shared among the routers in the group making it more cost effective than keeping backup routers and connections without using them.

How does GLBP work?

GLBP takes an "active approach" to first hop redundancy. A single router is elected the Active Virtual Gateway based on GLBP priority and assigns itself and others virtual MAC addresses. Hosts are assigned the most available router to them by the AVG and provided with its MAC. This router is known as the host's Active Virtual Forwarder.

What multicast address is used by GLBP routers to maintain hellos?

How would you find the routing table on a PC?

Typing the command "route print" into the command line.

True or false? An IP address ending in .255 will always be a broadcast address.


Depending on the subnet mask, .255 could be an address in the middle of a range that extends beyond the last octet.

What types of IPv4 addresses are there?

Usable - to

Multicast - to

Experimental - to

What is APIPA and what is its address range?

Hosts use Automatic Private IP Addressing to assign themselves an IP address when none are available on a network. Addresses range from to and hosts query the network to ensure there are no APIPA conflicts. Only hosts with APIPA enabled will be able to communicate.

What IP address range is used for testing/ teaching purposes? to

To what address are EIGRP updates sent?

What is RIPv2

RIPv2 is a distance vector routing protocol with hybrid characteristics. Improvements over RIP include classless addressing, multicast updates, update authentication, and a max hop count.

What is RIPv2's multicast address and max hop count? and 15.

How do adjacencies keep their link alive?

In OSPF, neighbors exchange hellos using multicast This is also the multicast an elected DR would send to all the routers containing LSAs.

What is the IPv6 loopback address?


What is IPv6 Anycast?

Multiple devices are assigned the same IPv6 address and when data is sent, it is received only by whichever device is closest.

What command can be entered in IOS to prevent logging messages from interrupting your work?

global config > (specify line) > logging synchronous

How is domain lookup disabled in IOS?

global config > no ip domain-lookup

True or False: Separate subnet/ router = separate broadcast domain?

False. A separate broadcast domain pertains to specifically Layer 2. All routers pass VLAN 1 by default meaning a broadcast will transcend a subnet because VLAN 1 is routed. Each subnet should be VLAN'd separately.

What command might be used to verify the configuration of a trunk or trunks?

show interfaces trunk

How many VLANs are possible total?


1 - 1005 are "normal range"

1006 - 4094 are "extended range"

What command is used to revert an interface back to its original configuration?

default interface (specify int)

In IOS, how do you view what was recently configured?

show history

How is a router's interface configured for a VLAN?

(in interface configuration mode) encapsulation dot1q (vlan #)

If CDP is enabled, what does the command 'show cdp neighbor' display?

It displays devices/ their host names and which port they're connected to. This is useful when first configuring devices.

What command identifies exactly what equipment you're working on?

show ver

How do you configure multiple interfaces at once in IOS?

In global configuration: interface range (x) -(y)

What protocol uses both TCP and UDP?

DNS on port 53.

In terms of loopback interfaces, what is a secondary?

A separate address within a loopback - a sub interface that can be configured with its own address.

What protocol uses both TCP and UDP?

DNS uses both on port 53. UDP is simply used to resolve names while TCP is used for synchronization of data between servers and clients.

What is PVST? What are its advantages?

Per VLAN Spanning Tree is a Cisco proprietary that runs spanning tree for each VLAN instead of physical switches. This allows for better load balancing as a trunk on a switch may be down for one VLAN but not another and will still be utilized. PVST is usually the default STP enabled on a switch.

What is the size of a PVST priority ID?

12 bits as opposed to the normal 16 bits. The remaining four bits identify the VLAN.

What is the difference between half and full duplex?

Bidirectional communication is possible with both, however it is only possible simultaneously with full duplex.

Explain Portfast.

Portfast bypasses the STP listening/ learning process completely and immediately begins forwarding. This is to enable immediate communication with end devices that don't send BPDUs.

What is BPDUguard?

When enabled, BPDUguard will put a portfast port in blocking if the switch receives any BPDUs from that port for the sake of security.

What is VTP?

VLAN Trunking Protocol transmits VLAN data over the network from a single switch acting as a server to other devices thereby automating the creation of VLANs on other switches.

What are the 3 modes of VTP?

1. VTP Server: switch can modify "vlan.dat" database file.

2. Client Mode: Listens for and applies changes made by switch

3. Transport Mode: Relays changes to database by VTP server but does not apply them to itself

What addressing scheme do PDUs at layer 2 use?

Frames will use destination and source MAC addresses.

What is CSMACD?

Carrier Sense Multiple Access with Collision Detection is an older networking technology. If a collision occurs, devices stop transmitting for a specified number of milli-seconds after which time the collision is unlikely to reoccur.

Define VLAN(ing).

Virtual Local Area Networks are logical separations that can span across multiple physical switches essentially creating a virtual switch. A VLAN is considered a broadcast domain.

Where are VLANs stored on a switch?

Stored in the "vlan.dat" database file located in NV-RAM.

What does Cisco IOS stand for? What three types of memory do Cisco devices use?

IOS = Internetworking Operating System

Devices use:

RAM: contains running-configuration

Non-volatile RAM: contains startup-configuration

Flash: contains IOS

What is a link in relation to a switch? What types of links are found on a switch?

Link is synonymous with switch port.

1. Access: carries/ is part of only a single VLAN

2. Trunk: carries traffic among multiple VLANs

What is the MTU for standard Ethernet?

15 KB

What might be the cause of collisions on a switch port?

Speed or duplex mismatch are common culprits.

How does a trunk port work?

Frames are tagged with information identifying the VLAN with which they are associated.

What are the two types of trunking protocols and their characteristics?

ISL (InterSwitch Link) - a Cisco proprietary protocol that encapsulates a frame with 30 byte frame containing the VLAN ID

IEEE 802.1q - an open standard that inserts an additional 4 bytes into the existing frame containing the VLAN ID

What is a native VLAN?

The VLAN allowed to pass a trunk without identifying information. This is only available when using dot 1q.

How does a switch operate?

- Switches populate MAC addresses by cross referencing the source MAC in a frame with its originating port. This is the only way they learn.

- Switches forward based on destination MAC.

- If a destination is unknown, the frame is flooded out to all port except the originating (this a unicast, not a broadcast!)

All hosts connected to a switch are on the same ___________.

Data Link/ Bridge

What is DTP?

Dynamic Trunking Protocol creates trunks automatically between two connected switchports.

What are the three modes of DTP?

1. Dynamic Desirable: ports in this mode will send and receive DTP frames (this is default on models ending in 50)

2. Dynamic Auto: ports in this mode will respond to DTP frames but not facilitate them (default for models ending in 60)

3. On: sets port to trunk unconditionally

What command will bring up in depth information on how a specific interface is configured?

show run interface (#)

What does the command 'show ip aliases' produce?

A list of all configured IP addresses on the device and the interfaces/ lines to which they are assigned.

How can you get to the front of a line in IOS?


When subnetting, how can the network block be determined?

The last host bit's decimal value will indicate the size of each network.

How can administrative distance be used when entering a static route?

Adding an administrative distance at the end of a static route in IOS greater than 1 can give another static route to the same destination priority over it. In the event that the preferred static route's interface goes down, the route with a greater distance can be used as backup.

How can a list of static routes be viewed in IOS?

show ip route static

How is a specific SLA assigned to a static route?

1. At the end of the route, enter track (#)

2. Configure the newly created track for a specific SLA by typing track (#) rtr (sla's #)

Static routes do not maintain hellos to keep a link alive. What are the steps to emulate this functionality using an SLI?

1. In configuration mode, configure a new SLA by using the command ip sla (#)

2. Now in sla config mode, ICMP echo should be specified using the command icmp echo (destination interface's IP)

3. Echo config mode will now be up, timeout an be specified in milliseconds simply using timeout (#) and frequency of ping in seconds using frequency (#)

4. The SLA can now be enabled using ip sla schedule (#) start-time now life forever

A measure of the dependability of the network components


Indicates how secure a network is.


Measure of the probability that a network would be available.


What is delay?

How fast data is moved across the network. This must not be confused with bandwidth, which is the size of the network medium.

Throughput/ data rate is synonymous with:


How is a static route relayed in an EIGRP topology?

When in router config mode, use redistribute static.

In an IPv6 packet, which field specifies TTL?

Hop Limit.

How can an EUI-64 address be configured automatically for an interface?

ipv6 enable in interface configuration.

Which VLANs are allowed on newly created trunks?

All are initially allowed until restricted by the user.

What must be remembered when connecting two trunk ports in 'on' mode?

These ports are on unconditionally and will not negotiate a new trunking protocol. Therefore, both sides of the trunk must have a matching trunking protocol pre-configured. Additionally, while it is useless in this type of situation, negotiation is still enabled by default in on mode and is sending useless DTP frames.

What is the primary purpose of STP?

Spanning Tree Protocol prevents logical loops when redundant links are present. Certain links are blocked and root bridges are elected to best suit the flow of traffic.

What are Broadcast Domains?

A broadcast domain is the area of a network through which a single broadcast can propagate. Typically routers are the end of the line for a broadcast, however, a routed VLAN is considered a broadcast domain itself.

What are Collision Domains?
A collision domain is ANY area of a network where communication can collide in half duplex. This includes each and every switch port. Hubs are considered a single collision domain.

What 3 steps are involved in the STP process?

1. Elect a Root Bridge for each Layer 2 domain.

2. Elect a Root Port on each non-root switch.

3. Elect 1 Designated Port per segment.

How are STP ports, segments, and bridges selected?

In order of succession (all determined by lowest vlaue):

1. Root Bridge ID

2. Root Path Cost

3. Sender Bridge ID

4. Sender Port ID

What are BPDUs?

Bridge Protocol Data Units are exchanged by every switch and port in an STP environment and contain the identifying metrics used in the STP process.

What is the Bridge ID?

This is the sum of a switch's MAC address and 16 bit priority. The priority is 32,768 by default.

What is Root Path Cost?

After a root bridge is elected, each non-root switch is evaluated given its distance from the root and assigned a cost.

Link costs -

10Mbps: 100 100Mbps: 19 1Gbps: 4

What is Sender Port ID?

Should two or more ports have the same bridge ID (redundant connections), the port numbers are examined.

What are the 3 states STP bridges go through before forwarding traffic?

1. Blocking (20 seconds) - No data exchanged except BPDUs

2. Listening (15 seconds) - STP election process

3. Learning (15 seconds) - MAC address table is populated by flooding and negates the need to do so once forwarding begins

Ports now enter forwarding.

What is the primary purpose of Layer 2?

The Data Link Layer controls communication between 2 devices on the immediate physical link.

At what layer is CDP?

Cisco Discovery Protocol is an Ethernet multicast at Layer 2.

As a network administrator, how would you confirm end device connectivity?

1. Pinging loopback address to verify TCP IP protocol.

2. Pinging local interface IP to verify NIC connectivity

3. Pinging gateway

4. Pinging the network nodes

What is HTTP? HTTPS?

Hyper Text Transfer Protocol is used to display websites TCP 80

Hyper Text Transfer Protocol over SSL is a secure version of HTTP TCP 443

What is POP?

Post Office Protocol is a method of connecting to/ receiving mail from a mail server on a client.

TCP 110

What is Telnet?

A protocol that uses TCP 23 to connect via CLI.

What is SSH?

Secure Shell is an encrypted/ secure method of connecting via CLI and uses TCP 22.

What is FTP?

File Transfer Protocol is used for basic data transfer and establishes its connection using TCP 21/ 20 before randomizing its connecting port.

What is DHCP?

Dynamic Host Configuration Protocol assigns IP addresses to end devices automatically over UDP 67/ 68

What is SMB?

Server Message Block (AKA CIFS) is a Microsoft protocol that has become a standard that can be used universally over TCP 445 and UDP 137/ 138.

What is TFTP?

Trivial File Transfer Protocol runs on UDP 69 unlike FTP which only uses TCP. Despite using UDP, TFTP is still fairly reliable as it uses a check sum.

What is SNMP?

Simple Network Management Protocol analyzes nodes on a network and uses UDP 161/ 162

What is the purpose of EtherChannel?

EtherChannel allows for multiple connections between two switches to be aggregated logically into a single virtual link. This prevents spanning tree from shutting down links seen as redundant and allows for higher throughput between switches. Up to 8 can be combined, but it is advised not to bundle more than 6.

What is LACP?

Link Aggregation Control Protocol is IEEE 802.3ad/ 802.1AX and is an open standard that can be used on non Cisco devices for EtherChannel negotiation.

What is PAgP?

Port Aggregation Protocol is a Cisco proprietary method of negotiating an EtherChannel link.

True or False: Interfaces of different types can be used together in EtherChannel?

False. Interfaces must all be the same on both ends, as should switch configuration.

At the end of an ACL, there is a(n) ____.

Implicit deny all. If nothing has been specified as permitted, all traffic will be denied.

When using OSPF or RIP, which command can be used to redistribute a manually configured default route?

(In OSPF configuration mode on the router with the route) default-information originate

When creating an ACL based on source TCP, what purpose does the "established"statement serve at the end of a line?

The established statement verifies incoming segments are truly originating from within a network (and not spoofed) by referencing the layer 4 peripherals (ie ACK, SYN, FIN etc) and dropping any suspicious segments without them.

What settings must be enabled on a terminal interface to allow for a direct connection using a console cable?

Bits per second - 9600

Data bits - 8

Parity - none

Stop bits - 1

Flow control - none

What methods are available to administrate APs?

Autonomous AP - configuration is local

Controller AP - configured/ controlled by server

"Instant" - one AP on network chosen as controller

Cisco Meraki - cloud/ browser based

What IOS command is used to display a MAC address table?

show mac address-table

What is DHCP snooping?

DHCP snooping is a security measure that can be enabled on specific switch ports or a VLAN. When enabled on a port, DHCP snooping prevents any inbound traffic attempting to assign addresses via DHCP from passing.

What is NTP?

Network Time Protocol is run on a network to ensure all network devices are synced with the correct time, without which, communication and logging may not work properly. This is usually run as a network service on a domain server. There are publicly available NTP servers online that are synced with atomic clocks.

What is CEF and why is it significant?

Cisco Express Forwarding is a protocol that must be enabled on Cisco devices running MPLS. This is enabled by default but can be turned on using the command ip cef

What are P, PE, and CE Routers?

CE - Customer Edge Routers sit on the customer of demarcation between an ISP and the customer.

PE - Provider Edge Routers sit on the customer of demarcation between an ISP and the customer.

P - Provider Router

What is needed to route a segment?

A source/ destination IP/ MAC, and port number

EIGRP measures by ______, RIP by _______, and OSPF by _______.

EIGRP - Metrics

RIP - Hop Count

OSPF - Cost

When configuring RIP or EIGRP what MUST not be forgotten?

no auto-summary without which, networks will be transmitted without masks otherwise.

What is a passive interface and what are its uses?

Passive Interfaces are specified interfaces on a router that will receive but will not send routing updates. The command (in router configuration mode) is passive-interface (int#)

What algorithm does RIP use?

Bellman Ford

What is DUAL?

Diffused Update Algorithm which is utilized by EIGRP to calculate metrics.

Which routing protocol converges considerably quicker than the others?


The 5 DUAL K values include:

Primarily Bandwidth and Delay but also Reliability, Load, and MTU

What range of Autonomous Systems can be used?

1 - 65,535

What do P's and A's indicate in the EIGRP topology table?

Passive - this network route is connected and routable

Active - this network is not routable and the local router is actively seeking a route to it.

Regarding wildcard bits, EIGRP configuration, and CCNA simulation, it is crucial to:

Read the question carefully. CCNA has typically not asked that wildcard masks be used in configuring EIGRP, however, it is very important to know what is being asked.

Unlike OSPF, EIGRP hello timers ________.

Do not need to match.

What is the default speed of a serial interface?

1.544 Mbps

How many hope counts does OSPF use?

An infinite amount.

What happens if a single OSPF link goes down?

Every single router within its area must reapply the shortest path first algorithm to recalculate.

What three tables does OSPF create?




What is an LSU?

Updates regarding topology after network is already initialized. Sent to be stored in the OSPF database.

On serial interfaces, OSPF priority is:

0. Because of this there is no election process on serial point to point networks.

How is an OSPF router ID changed in the CLI?

(config int) ip ospf priority (#)

How do you view the OSPF database? What does this contain?

sh ip ospf database This displays your OSPF router id, configured IP addresses, areas, and learned networks/ their age.

What is the difference between a bridge and a switch?

A bridge is intended to segment a network while a switch offers further functionality.

In order to use Telnet or SSH to connect into a switch, what else must be set besides an IP address?

A default gateway

What is LLDP?

Link Layer Discovery Protocol is a network mapping/ discovery protocol that is very similar to CDP. Unlike CDP it is an open standard, but both are designated under IEEE 802.1AB

What is STP's IEEE designation?


What is the default STP priority number? By what increment can a priority be changed?

32,769 is the default; 4096 is the increment. Additionally, the VLAN number for the spanning tree is added to the priority (so 32,769 is technically 32,768 plus the default VLAN of 1)

What must be assigned on a switch in order for a VTP server/ client configuration?

A domain name and an IP address .

What command can be used to view general information about a switch's VTP configuration? What are four important pieces of information displayed?

sh vtp status

- Domain name

- VTP Mode

- Last time configuration was modified

- Current configuration revision

What is the IPv6 equivalent of APIPA addressing?

Link Local Addresses

What command is used to enable IPv6 on a router?

ipv6 unicast-routing

What is the multicast address for RIPng?


What is the multicast address for EIGRP in IPv6?


What is the multicast address for OSPFv3?

FF02:5 & 6

What routing protocols are used in IPv6?

RIPng (next generation)



Prior to configuring IPv6 interfaces with EIGRP, what commands should be used?

1. (in global config) ipv6 router eigrp (#)

2. (now in router config mode) no shutdown

3. eigrp router-id (ID in IPv4 format)

Now the command ipv6 eigrp (#) can be used on each interface.

Prior to configuring IPv6 interfaces with OSPF, what commands should be used?

1. (in global config) ipv6 router ospf (#)

2. (now in ospf config mode) router-id (ID in IPv4 format)

Now the command ipv6 ospf (#) area (#) can be used on each interface.

What is Dual Stack?

Networking equipment running both IPv4 and IPv6 simultaneously.

What are the four categories of NAT addresses?

Inside Global - the public address to which internal addresses are translated

Inside Local - a node's internal address

Outside Local - the destination node's internal address before NAT
Outside Global - the destination's publicly translated address

What is CPE?

Customer Premise Equipment is the equipment in a network owned and maintained by the ISP customer.

What is a local loop?

The connection from the point of demarcation to the central office.

What is the POP?

Point of Presence is another term for central office.

What is a toll network?

The series of routers and switches that transports traffic from point A to point B.

What are the three WAN connection types?

Leased Lines: a dedicated and constant connection (T1, T3, PVCs)

Circuit Switching: ISDN and dial up

Packet Switching: Frame Relay, X.25, MPLS

What are the 3 main WAN encapsulation types?




Using CHAP, the username on the local router should be:

The remote router's hostname.

What should be remembered when using frame relay in conjunction with RIP?

To use sub interfaces, because due to split horizon, interfaces cannot receive updates regarding a down link out of the same interface.

What is GRE?

Generic Encapsulation Tunnels can encapsulate any routed protocol but use plain text to do so and are therefore insecure.

What is RADIUS?

Remote Access Dial-In User Service is a protocol that allows remote devices to connect to a single AAA server located on a network. This server can be used to unify authentication for several administrative and network connected devices. RADIUS can be used internally, through WiFi, or over a VPN.

What is TACACS?

Terminal Access Control Access-Contol System is a protocol with similar functionality to RADIUS. Today, TACACS+ (Cisco proprietary) is used which incorporates Authorization and Accounting along with response codes.

What does AAA stand for?

Authentication, Authorization, and Accounting

What are the most common ports used by RADIUS?

UDP 1812 and 1813

RADIUS encrypts:

Only the password field.

What is the main advantage that TACACS has over RADIUS?

It uses TCP whereas RADIUS uses UDP and encrypts all data.

What is the RFC and port number of TACACS?

RFC 1492 and port 49

What is the FEC?

In MPLS, the Forward Equivalency Class categorizes each network/ label.

What is CEF?

Cisco Express Forwarding is a protocol that runs MPLS on an LSR.

How is CEF turned on?


What is LDP?

Label Distribution Protocol is the backbone of MPLS.

As traffic moves through an MPLS network, labels are _____ and _____ and finally _____ when the destination LSR.

1. Pushed

2. Swapped

3. Popped

What is BGP?

Border Gateway Protocol is a routing protocol often utilized by ISPs or large enterprise networks. Similar to EIGRP, it establishes neighboring routers before forwarding. BGP is unique in that it is a "path vector" routing protocol and uses TCP - specifically port 179.

What is a route reflector?

The term for neighboring BGP routers. Interestingly, these routers are not required to be on the same subnet.

Which version of BGP is commonly in use today?


How are neighbors formed in BGP?

Neighbors must be explicitly specified by a network administrator, there are no solicitations.

EIGRP emphasizes _____ while BGP emphasizes_____.

Fast convergence