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So we need to find this DLY value needed for the metric that has to be 3 times worse. To affect the formula we’re really left with just the DLY part, because changing the BW can affect other routing protocols as well as QoS. So the formula is correct! Now the path through R3 had to be three times worse for R1 to do a 1:3 ratio. Using the above information from the topology table, we can verify the formula: metric = 256 * (10^7/1000000+2) The formula is this with default K-values: metric = 256 * (10^7/minBW+sumDLY)ĭLY is in tens of microseconds. State is Passive, Query origin flag is 1, 2 Successor(s), FD is 3072ġ0.0.12.2 (GigabitEthernet1.12), from 10.0.12.2, Send flag is 0x0Ĭomposite metric is (3072/2816), route is Internalġ0.0.13.3 (GigabitEthernet1.13), from 10.0.13.3, Send flag is 0x0ĮIGRP only uses BW and DLY for its composite metric calculation. What if we wanted to do a ratio of 1:3 where the one part is through R3? Now let’s see the metric that R1 is currently using as a baseline for our calculation. Without jumping to the CLI, we see that R1 will do ECMP for 10.0.23.0/24. But what if you’re asked to do some sort of ratio of load sharing? Let’s have a look at a very simple three router topology: The alternate path still must be a FS, though (RDhave a look at an EIGRP Hello packet: IANA defines a list of the reserved addresses. To become neighbors only a few parameters of the Hello packet must match:Īs soon as you see a Hello packet from a neighbor and the Hello parameters match, you’re adjacent and can start exchanging updates.ĮIGRP uses the link local multicast address 224.0.0.10 to discover and establish neighbors. EIGRP is a simple distance vector protocol.