CCNA 3 and 4 Companion Guide third edition Chapter 4 Enhanced Interior Gateway Routing Protocol pg 144: Quizz question 9
- How does EIGRP prevent routing loops from occurring with external routes?
A. By rejecting external routes that are tagged with a router ID identical to their own B. By storing the identities of neighbors that are feasible sucessors C. By rejecting all eighboring routers that have an advertised composite metric that is less than a router's best current metric D. By storing all neighboring routes that have loops identified in the routing table.
Answer : D
I wonder how does EIGRP identifie external route loop in the routing table! Moreover, why would EIGRP store all neighboring routes that have loops identified in the routing table ? Isn't useless willing to forward a packet through a route loop stored in a routing table ?
By the way how does DUAL prevent routing loops from occuring with external routes, i.e. routes that are sourced outside of the EIGRP AS ? Since those external routes are possibly from IGRP, RIP, another EIGRP AS or even static, DUAL hasn't the same information from these routes as it does with routes sourced within the same AS. How does DUAL cope with this ? What is the DUAL mechanics ?
I would preferably go for answer C.
Do you ?
bhe