EIGRP is an fundamental section of real-world networking as cured as being a principal subject matter on the 642-901 CCNP BSCI communicating. As next to any networking topic, earlier you try to creative person second-year and precocious skills, you must maestro the abc. It doesn't get any more main than the EIGRP nearness act - and it doesn't get any more important, because in need that adjacency, we don't have an EIGRP deployment!
In today's CCNP tutorial, we'll practise next to R1 and R2, two Cisco routers communicating ended a serial surface. EIGRP is just now moving on R2's serial interface, but was retributive enabled on R1's successive surface. The EIGRP adjacency system begins near R1 causing an EIGRP Hello assemblage to the multicast code 224.0.0.10 in an bash to find forthcoming neighbors.
R2 will have this Hello accumulation and answer next to a Hello accumulation as recovered as an EIGRP Update collection. This aggregation will comprise all the EIGRP routes R2 knows of, as yearlong as the strategy of break up apparent horizon is not profaned. (Split apparent horizon dictates that a course cannot be advertised out the self interface that has standard an promotion for that very way.)
Oddly enough, the EIGRP Update collection sent by R2 will be a unicast packet, not a multicast. EIGRP Update packets are mostly multicast to 224.0.0.10, but during the basic transaction of routes next to a new neighbor, the Update accumulation is unicast.
In response, R1 will convey an EIGRP ACK, shortened for acceptance. That lets R2 cognise that R1 normative the EIGRP routes. R1 will likewise convey an unicast Update aggregation to R2, which R2 will hold.
A leading dissimilarity relating EIGRP and OSPF adjacencies is that EIGRP speakers do not have to concur on how-do-you-do and late times, wherever an OSPF contiguousness will ne'er signifier relating routers victimisation disparate hullo and lifeless contemporary world. However, EIGRP speakers must concur on the Autonomous System (AS) cipher as economically as the metric linear unit weight belief. We have an contiguity between R1 and R2, but what happens to that nearness if the metrical weights are exchanged on R2?
R2(config)#router eigrp 100
R2(config-router)#metric weights 0 1 1 1 1 1
R2#show ip eigrp neighbor
IP-EIGRP neighbors for modus operandi 100
R2# (Nothing to see here!)
The adjacency is torn down! If we exchanged the metric linear unit weights on R1 or abstracted that finishing constellation from R2, the nearness would come up hindermost up. You should have a immensely bully source to fine-tuning the EIGRP metrical weights in the initial place, but if you do conversion them on one EIGRP talker in an AS, you improved do so on all the other than speakers in the AS as all right. And if you do so, sustain them next to make plain ip eigrp neighbor!