Etric weights on R1 or eliminated that final configuration from R2, the adjacency might come again up. You need to have a wonderful cause to alternate th

EIGRP is an important a part of actual-worldwide networking similarly to being a primary subject matter at the 642-901 CCNP BSCI examination. As with any networking problem depend, earlier than you try to master intermediate and superior abilities, you need to grasp the basics. It could now not get any extra essential than the EIGRP adjacency procedure - and it does not get any extra crucial, due to the fact with out that adjacency, we don't have an EIGRP deployment!

In today's CCNP educational, we're going to artwork with R1 and R2,  Cisco routers speaking over a serial interface. EIGRP is already strolling on R2's serial interface, but changed into just enabled on R1's serial interface. The EIGRP adjacency system begins with R1 sending an EIGRP Hello packet to the multicast address 224.0.0.10 in an try and find capacity friends.

R2 will get hold of this Hello packet and respond with a Hello packet similarly to an EIGRP Update packet. This packet will consist of all the EIGRP routes R2 is aware of of, as long as the guideline of cut up horizon isn't always violated. (Split horizon dictates that a direction can not be advertised out the same interface that has acquired an advertisement for that same path.)

Oddly sufficient, the EIGRP Update packet transmitted with the resource of R2 will be a unicast packet, no longer a multicast. EIGRP Update packets are typically multicast to 224.Zero.Zero.10, but in the course of the number one trade of routes with a brand new neighbor, the Update packet is unicast.

In reaction, R1 will send an EIGRP ACK, quick for acknowledgement. That we ought to R2 realize that R1 acquired the EIGRP routes. R1 might also even send an unicast Update packet to R2, which R2 will famend.

A critical difference between EIGRP and OSPF adjacencies is that EIGRP audio system do not have to agree on howdy and dead instances, wherein an OSPF adjacency will by no means shape among routers the usage of certainly one of a kind hi there and lifeless instances. However, EIGRP audio system have to agree at the Autonomous System (AS) quantity in addition to the metric weight values. We have an adjacency between R1 and R2, but what takes place to that adjacency if the metric weights are modified on R2?

R2(config)#router eigrp a hundred

R2(config-router)#metric weights 0 1 1 1 1 1

R2#display ip eigrp neighbor

IP-EIGRP buddies for gadget 100

R2# (Nothing to look proper here!)

The adjacency is torn down! If we modified the metric weights on R1 or eliminated that final configuration from R2, the adjacency might come again up. You need to have a wonderful cause to alternate the EIGRP metric weights in the first place, however if you do exchange them on one EIGRP speaker in an AS, you higher accomplish that on all of the different audio system in the AS as properly. And if you acquire this, confirm them with show ip eigrp neighbor!

Chris Bryant, CCIE #12933, is the owner of The Bryant Advantage, home of over 2 hundred unfastened certification exam tutorials, which include CCNA certification training articles. His different CCNA have a look at guide is likewise available!

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