Figure 813 Enhanced IGRP and Query Scoping

Router D1 has 16 remote sites connected to it via Frame Relay; each remote router advertises subnets from 131.108.1.0/24 to 131.108.15.0/24. D1 has all the specific routes in its routing table and can easily summarize all the subnets toward D2 and D3. If Ethernet 0 is the interface that connects D1 to D2 and D3, the interface configuration for Ethernet 0 on D1 would be as follows:

interface e 0

ip address 131.108.22.1 255.255.255.0 ip summary-address eigrp 1 131.108.0.0 255.255.240.0

router eigrp 1 network 131.108.0.0

With this configuration, whenever one of the remote subnets flaps, D1 will send queries to all its connected neighbors. Upon receiving the query, D2 and D3 will not propagate the query any further because they do not have specific routes in their tables—they have only a single summary via D1. Upon receiving the query, D2 and D3 will send an unreachable message back to D1.

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