![]() Note that the only real EIGRP data in the packets are the K values, the EIGRP AS, and the type of packet (hello). The normal hello that router4 had been generating… Note: I’m filtering out some packets because of the way the lab is setup, hence some of the packets sequence orders in the capture aren’t consecutive. Let’s walk through this one packet at a time to get an understanding of what happened… Now, let’s bring the interface back online and see what happens… Note that they are occurring every 5 seconds and that they are being sent to the multicast address of 224.0.0.10. If we look at the traffic on that segment, we’ll see router4 sending its regular hello messages out onto the segment… Now, we’ll start with the 10.0.0.26 interface on router5 being shutdown. Let’s use the same topology as last time… Let’s take a look at the initial peering of two EIGRP routers and then see how they exchange routes. This is done through the use of update packets. So once an adjacency forms, the routers need to exchange routing information with each other. Hellos are Multicast to the address of 224.0.0.10. It should also be noted that these timers do NOT need to match in order for an adjacency to form. ![]() If the hold timer expires, it means that the router has lost connectivity to its peer router. It should be noted here that there is also a hold timer that is ,by default, 3 times that of the hello timer. Hello packets are sent ,by default, every 5 seconds and every 60 seconds on T1 and slower WAN links. Routers will first start off by exchanging hello packets with each other. If all of these items are in order, a adjacency will be allowed to form. ![]() The big hitter is the K values for the metric calculation must match. That’s not a terribly long list considering that I listed some rather obvious ones in there. The K values, if changed from the defaults, need to match The interfaces must not be in the passive list Routers must share a common subnet (Primary interfaces are on the same subnet, secondary interfaces don’t count). The routers must be in the same EIGRP AS (AKA router eigrp 1) In this post, I want to talk about how EIGRP neighbors interact with each other.įirst lets start by solidifying the requirements for two routers to become neighbors, or to become adjacent. In the first post, we talked about some of the basics of EIGRP.
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