Cisco Systems 78-11741-02 manual IPC-270

Configuring EIGRP

EIGRP Configuration Task List

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

10.3.1.0/24

Corporate network

10.2.1.0/24

Distribution

router 1

(hub)

Distribution

router 2

(hub)

Remote

router

(spoke)

10.1.1.0/24

46095

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.

Cisco IOS IP Configuration Guide

IPC-270