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Configuring EIGRP
EIGRP Configuration Task List
IPC-270
Cisco IOS IP Configuration Guide
Dual-homed routing can introduce instability into an EIGRP network. In Figure 50, distribution router
1 is directly connected to network 10.3.1.0/24. If summarization or filtering is applied on distribution
router 1, the router will advertise network 10.3.1.0/24 to all of its directly connected EIGRP neighbors
(distribution router 2 and the remote router).
Figure 50 Dual-Homed Remote Topology With Distribution Router 1 Connected to Two Networks
Figure 50 shows a simple dual-homed remote router where distribution router 1 is connected to both
network 10.3.1.0/24 and network 10.2.1.0/24.
If the 10.2.1.0/24 link between distribution router 1 and distribution router 2 has failed, the lowest cost
path to network 10.3.1.0/24 from distribution router 2 is through the remote router (see Figure 51). This
route is not desirable because the traffic that was previously traveling across the corporate network
10.2.1.0/24 would now be sent across a much lower bandwidth connection. The over utilization of the
lower bandwidth WAN connection can cause a number of problems that might affect the entire corporate
network. The use of the lower bandwidth route that passes through the remote router might cause WAN
EIGRP distribution routers to be dropped. Serial lines on distribution and remote routers could also be
dropped, and EIGRP SIA errors on the distribution and core routers could occur.
Corporate
network
10.3.1.0/24
Distribution
router 1
(hub)
Distribution
router 2
(hub)
Remote
router
(spoke)
10.2.1.0/24
10.1.1.0/24
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