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