Chap 2 - EIGRP Flashcards
What are 5 characteristics of EIGRP?
* Fast convergence * Uses neighbors and Hello messages * Composite metric * Only sends update messages when there’s a change * Equal and Unequal cost load balancing
What 4 characteristics describe an EIGRP Autonomous System?
* A single router can run multiple EIGRP instances * Represents a common router domain * Routers exchange routes only with other routers in its AS * All routers in an AS use the same metric calculation formula
What is an EIGRP PDM and what is its function?
* Protocol Dependent Module - each routed protocol has its own PDM. * IPV4 * IPV6
What is a Successor Route?
The route with the lowest path metric to reach a destination.
What is a Successor?
The first next-hop router for the successor route.
What is the Feasible Distance (FD)?
The metric value for the lowest-metric path to reach a destination.
What is the Reported Distance (RD)?
Distance reported by a router to reach a prefix. The reported distance value is the feasible distance for the advertising router.
What is the Feasible Condition?
For a route to be considered a backup route, the RD received for that route must be less than the FD calculated locally. This logic guarantees a loop-free path.
What is a Feasible Successor?
A route with that satisfies the feasibility condition is maintained as a backup route. The feasibility condition ensures that the backup route is loop free.
What 4 items are in the Topology Table?
* Network prefix * EIGRP neighbors advertising that prefix * Metrics from each neighbor (RD and hop count) * Values used by the neighbor when calculating the metric
In the topology table what are the 2 numbers in parenthesis?
( FD / RD ) The local router’s Path Metric if it were to use that route / The RD or the neighbors feasible distance to the destination
What is EIGRP’s multicast MAC address?
01:00:5e:00:00:0a
With is EIGRP’s multicast address?
224.0.0.10
What is EIGRP’s port number?
IP 88
What are EIGRP’s 5 message types?
* Hello * Query * Request * Update * Reply
When is the Query message sent?
When EIGRP is searching for another path during convergence
What protocol does EIGRP use for reliable communication?
Reliable Transport Protocol (RTP)
How does RTP ensure reliable communication?
* Ensures packets are delivered in order * Ensures routers receive specific packets * Sequence number of 0 does not require an acknowledgement * All other sequence numbers require an ACK
Which message types are considered reliable and which are not?
* Update, query, reply, and unicast packets are reliable and require an ACK * Hello’s and ACKs are not reliable
What happens if an originating router doesn’t receive an ACK before the retransmit timeout timer expires?
* Originating router notifies non-acknowledging router to stop processing multicast packets and switch to unicast * Routers then communicate via unicast until neighbor is fully synchronized * Once synchronized the originating router notifies the neighbor to return to multicast
How many times will EIGRP retry?
16 times
What does EIGRP do if, after 16 attempts, it doesn’t receive an ACK?
It resets the neighbor relationship
What is the difference between RTP and other reliable-transport protocols like TCP?
RTP supports multicast, the others do not.
What 4 parameters must match before EIGRP neighbors can form?
* K-values * Primary subnet * ASN * Authentication parameters
5 Benefits of EIGRP Named Mode
* All EIGRP configuration occurs in one location* Supports current EIGRP features and future developments. * Supports multiple address families (including Virtual Routing and Forwarding [VRF] instances) * EIGRP named configuration is also known as multi-address family configuration mode * Commands are clear in terms of the scope of their configuration.
What are the 3 subsections of EIGRP Named Mode?
* Address family * Topology * Interface
What 4 things can be configured in the Address family subsection?
* Network statements * K-values * Logging settings * Stub settings
In the Interface Subsection what are 2 ways to assign commands to interfaces?
* By specifying the interface and making changes to that one interface * By specifying ‘default’ which will apply the settings to all EIGRP interfaces
In the Interface Subsection what 4 things can be configured?
* Hello interval * Split horizon * Summary routes * Authentication settings
In the Topology Subsection what 2 things can be done?
* Redistribution * Administrative Distance settings
What are 3 steps in enabling EIGRP Named Mode on an interface?
* Initialize the EIGRP process R1(config)# router eigrp NAME * Select the address-family and create the ASN - R1(config-router-af)# address-family ipv4 autonomous-system 1 * Select the interface with the network cmd R1(config-router-af)# network 10.20.30.0 0.0.0.255
If you have a router running EIGRP Named Mode with an AS of 12 can the configuration be changed without having to go through the address-family?
No, classic mode and named mode are independent. Even if the ASN is the same you can’t make changes to Named Mode using Classic Mode commands
What does the network command do?
Selects the interface whose connected network will be added to the topology table and be advertised
How are secondary networks added to the EIGRP Topology Table?
They must be redistributed into it.
What network statement would enable EIGRP on all interfaces?
network 0.0.0.0 255.255.255.255
What is the command to set the router ID?
R1(config-router)# eigrp router-id 1.1.1.1
In EIGRP Named Mode under af-interface submode which commands take precedence - those under af-interface default or those under af-interface gig0/1?
af-interface gig0/1 will over-ride anything in Default
Does a passive-interface show up in ‘show ip eigrp interfaces’ ?
No
What does EIGRP authentication encrypt?
Just the password
What are the 3 steps for creating a keychain for EIGRP authentication?
* Create the key-chain R1(config)# key chain MYKEY * Assign a key identifier R1(config-keychain)# key 1234 * Assign a key string R1(config-keychain-key)# key-string cisco
In EIGRP classic mode what 2 commands go on the interface to enable authentication?
* ip authentication key-chain eigrp 4 MYKEY * ip authentication mode eigrp as 4 md5
In EIGRP named mode what 2 commands go on the interface to enable authentication?
* R2(config-router-af-interface)# authentication mode md5 * R2(config-router-af-interface)# authentication key-chain MYKEY
What are EIGRP Wide Metrics scaled by?
65,535
In EIGRP Wide Metrics what is latency measured in?
picoseconds
What 3 things changed with Wide Metrics?
* Scaled by 65,535 * Delay measured in picoseconds * Added another k-value k6
What is the fastest link EIGRP Wide Metrics can support?
4.2 Tbps
What is the command to change the K values in Named Mode?
R1(config-router-af)# metric weights
How is variance calculated for unequal cost load balancing?
Feasible Successor FD / Successor FD
