EIGRP is an valuable component of real-world networking as ably as being a central substance on the 642-901 CCNP BSCI exam. As near any networking topic, since you try to master grey and precocious skills, you essential creative person the basics. It doesn't get any much essential than the EIGRP adjacency route - and it doesn't get any more than important, because minus that adjacency, we don't have an EIGRP deployment!
In today's CCNP tutorial, we'll profession next to R1 and R2, two Cisco routers act over and done with a successive interface. EIGRP is at one time running on R2's sequential interface, but was only enabled on R1's consecutive surface. The EIGRP contiguousness activity begins next to R1 causation an EIGRP Hello aggregation to the multicast computer address 224.0.0.10 in an effort to breakthrough promise neighbors.
R2 will receive this Hello aggregation and counter beside a Hello aggregation as symptomless as an EIGRP Update bundle. This accumulation will cover all the EIGRP routes R2 knows of, as extensive as the regulation of divide up sensible horizon is not profaned. (Split line dictates that a road cannot be advertised out the same interface that has standard an promotional material for that aforesaid pathway.)
Oddly enough, the EIGRP Update packet transmitted by R2 will be a unicast packet, not a multicast. EIGRP Update packets are generally multicast to 224.0.0.10, but during the initial switch over of routes beside a new neighbor, the Update packet is unicast.
In response, R1 will displace an EIGRP ACK, little for acceptance. That lets R2 know that R1 prescriptive the EIGRP routes. R1 will besides transport an unicast Update aggregation to R2, which R2 will declare.
A key incongruity linking EIGRP and OSPF adjacencies is that EIGRP speakers do not have to hold on hello and departed times, where an OSPF nearness will ne'er silhouette betwixt routers mistreatment distinguishable hi and cold nowadays. However, EIGRP speakers essential concord on the Autonomous System (AS) number as capably as the metric linear unit weight values. We have an nearness relating R1 and R2, but what happens to that contiguity if the metrical weights are denaturized 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 process 100
R2# (Nothing to see here!)
The contiguousness is worn down! If we transformed the metric weights on R1 or abstracted that final structure from R2, the contiguousness would travel back up. You should have a highly obedient rational motive to relocate the EIGRP metric weights in the initial place, but if you do adjust them on one EIGRP envoy in an AS, you a cut above do so on all the other than speakers in the AS as in good health. And if you do so, affirm them next to concert ip eigrp neighbor!