At this point, we know that DUAL finds the successor(s) for each destination and attempts to find feasible[DU1] successors as well. As with successors, a router can have more than one feasible successor for a particular destination. Refer to Figure 1 for an example:

In addition to calculating the successor (best next hop), DUAL will also attempt to find one or more “feasible successors” (loop-free backup next hops) for each destination.

Welcome back! Continuing on with our discussion of EIGRP, let’s delve further into the details of what makes this particular Interior Gateway Protocol (IGP) so successful.

Interior Gateway Routing Protocol (IGRP) was a Cisco-proprietary Distance-Vector (D-V) classful routing protocol — basically an improved version of RIPv1. Like other D-V protocols, each IGRP router periodically flooded its routing table, but it differed from RIP in two ways. First, RIP’s advertisement interval was thirty seconds but IGRP’s was ninety seconds, which allowed IGRP to scale to larger networks than RIP. Second, RIP used a simple hop count metric, but IGRP’s more sophisticated metric was based on minimum path bandwidth and total path delay, with options to include link reliability and interface loading.

Let’s look at some additional options that can be used with EIGRP network statements. Refer to Figure 1: In order to get EIGRP running on all interfaces, we could do this: router eigrp 1 network 192.168.1.0 network 172.16.0.0 network 10.0.0.0 As a result, the interfaces would advertise the following prefixes (remember that automatic route summarization is enabled […]

Let’s now take a look at the interplay between network statements and auto-summary with EIGRP. Refer to the example topology: To get EIGRP running on the Fa0/1, Fa0/2 and Fa0/3 interfaces, we’ll use the following configuration: router eigrp 1 network 172.16.0.0 network 10.0.0.0 Like RIPv2, EIGRP is a classless protocol that performs automatic route summarization by […]

In packet switching networks, routing directs packet forwarding, the transit of logically addressed packets from their source toward their ultimate destination through intermediate nodes. These nodes are typically hardware devices called routers, bridges, gateways, firewalls, or switches. General-purpose computers with multiple network cards can also forward packets and perform routing, though they are not specialized […]