Week 13: EIGRP Flashcards
Why are K values important to remember?
a. They are values that can be changed to influence which routes are preferred.
b. Mismatched K values will cause routers using EIGRP to not form neighbors
What K Values should you change?
Bandwidth and/or Delay
What is the basic command syntax require to get EIGRP running?
a. Router eigrp (AS #)
b. Network (IP) subnet mask
What is a Feasible Successor and why is it important?
a. FS is the backup route EIGRP chooses to a destination network if the Successor goes down
b. They can be inserted into the routing table if a Successor route is down
What does it mean to be “Stuck in Active”?
a. The Successor route is down and there is no FS in the topology table
b. EIGRP has sent out a query to all neighbors looking for a route
c. The router becomes stuck in active because queried routers do not reply or if they do they do not provide a viable alternative route.
How would you troubleshoot an EIGRP peer not coming up?
a. Debug IP eigrp packets
i. This will show the error that is preventing the link from forming
b. I would look at the interface configuration to make sure that the interfaces on both sides are up.
c. Show run. I would look at the run config to determine that the EIGRP settings are correct and the right networks are being advertised.
d. I could use traceroute to see where the packet is being dropped.
What is EIGRP?
1) Enhanced Interior Gateway Routing Protocol, or EIGRP, is a Cisco proprietary, advanced distance vector dynamic routing protocol.
2) EIGRP uses the DUAL algorithm to converge very quickly
3) EIGRP knows each neighboring router’s routing tables and predefining primary and secondary routes to every destination network.
4) EIGRP, unlike OSPF, keeps secondary routes and doesn’t throw them away.
Administrative Distance for EIGRP
90
Hello timer for EIGRP
1) Every 5 seconds by default using multicast address 224.0.0.10
2) On slower T1 lines they are sent out every 60 seconds.
Hold Timer for EIGRP
Every 15 seconds by default and 180 seconds for slower T1 lines.
Passive Interfaces
Interfaces with the passive-interface command applied do not allow any routing updates or hellos out the interface. For EIGRP, this means that the router will not form adjacencies with connected routers on that particular port.
EIGRP Default Routes
They can decrease the size (and complexity) of the routing table by providing a path to all unspecified destinations.
EIGRP Metrics
Bandwidth – the lowest bandwidth value between the source and destination
Delay – the cumulative delay along a series of links
Reliability
Load
MTU
Why EIGRP over OSPF
1) ease of use
2) Rapid convergence
3) no taxing on bandwidth
4) route tables
5) summarization.
