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Flashcards in Ch 9 Deck (21)
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What is the Feasibility Condition?

If a non-successor route's Reported Distance is less than the Feasible Distance then the route is a Feasible Successor Route


What is the Feasible Distance?

The local routers Composite Metric of the best route to reach a subnet - as calculated by the LOCAL ROUTER.


What is the Reported Distance?

The next-hop router's best Composite Metric for the same subnet.



The route with the best metric, or best Feasible Distance. 'show ip route' shows the successor routes.


What is a Feasible Successor?

A route who's Reported Distance is less than the local router's Feasible Distance, if the best route fails EIGRP switches to the Feasible Successor.


What does DUAL stand for?

Diffusing Update Algorithm.


If a successor route fails what does EIGRP do?

Switches over to the Feasible Successor route, if no Feasible Successor route then DUAL takes over to find a new route.


What does DUAL do?

1.) The local router sends EIGRP QUERY messages to its remaining neighbors looking for a route 2.) the neighbor replys with an EIGRP REPLY message confirming a viable route 3.) The route is then entered in the local routers table.


What 3 steps does EIGRP do when first joining the network?

1.) Neighbor Discovery 2.) Topology Exchange 3.) Chooses Routes


What type of messages are used to discover neighbors?

Hello Messages


What type of messages are used to exchange topology?

EIGRP Update Messages


What address are EIGRP Hello messages sent to ?


What address are EIGRP Update Messages sent to ?

The Unicast address of the neighboring router. If multiple neighbors are on the subnet then to


What protocol does EIGRP use?

Reliable Transport Protocol (RTP)


What advantage does RTP have?

provides mechanism to resend any messages that were not received


What is the default Hello interval?

5 seconds


What is the Hold Interval

The amount of time a router will wait to hear a Hello from its neighbor before declaring it down.


What is the default Hold Interval

3 times the Hello time or 15 seconds.


How does EIGRP notify its neighbors of a topology change?

EIGRP Partial Update


What are the checks that EIGRP performs to determine if it can be a neighbor?

* passes authentication * Same Autonomous System number * Source IP address used by the neighbor to send Hello is on same subnet * EIGRP K-values must match


What is the formula EIGRP uses to calculate the Composite Metric?

Metric = ((10^7 / least-bandwidth) + cumulative delay) * 256