You have two routers connected to each other that are both running the EIGRP protocol. The routers have built a neighbor relationship and are exchanging routing information. You execute the following command on the EIGRP process on Router 1:
router1(config)# router eigrp 100 router1(config-router)# passive-interface
What will be the effect of this command?
- Only routing advertisements from Router 1 to Router 2 will be prevented.
- Only router advertisements to and from Router 1 will be prevented.
- All hellos and routing updates will be prevented, and the neighbor relationship between Router 1 and Router 2 will be broken.
- Hellos will be prevented, but routing updates will continue to be sent out.
The effect of the passive-interface command is dependent on the routing protocol. With RIP, the command prevents the sending of route updates, but does not prevent the reception of route updates. With EIGRP, the passive-interface command prevents both the sending and receiving of route updates, and also the sending of hellos. Without hello packets, the routers are unable to maintain the neighbor relationship, upon which all communications including route updates depend.
If the intent was to preventing routing updates from Router 1 to Router 2 while still allowing updates from Router 2 to Router 1, the routing updates must be filtered out and denied on Router 1 with a distribute list, as shown in the following command set:
router1(config)access-list 101 deny any router1(config)#router eigrp 100 router1(config-router)distribute-list 101 out
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Troubleshoot passive interfaces