Cisco Catalyst 4500 Series - Page 856

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Software Configuration Guide—Release IOS XE 3.6.0E and IOS 15.2(2)E
OL_28731-01
Chapter 34 Configuring Layer 3 Interfaces
Configuring EIGRP Stub Routing
Figure 34-5 Simple Dual-Homed Remote Topology
Figure 34-5 shows a simple dual-homed remote with one remote router and two distribution routers.
Both distribution routers maintain routes to the corporate network and stub network 10.1.1.0/24.
Dual-homed routing can introduce instability into an EIGRP network. In Figure 34-6, 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 advertises network 10.3.1.0/24 to all of its directly connected EIGRP neighbors
(distribution router 2 and the remote router).
Figure 34-6 Dual-Homed Remote Topology With Distribution Router 1 Connected to Two
Networks
Figure 34-6 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 using the remote router (see Figure 34-7). This
route is not desirable because the traffic that was previously traveling across the corporate network
10.2.1.0/24 is now 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
Corporate
network
Distribution
router 1
(hub)
Distribution
router 2
(hub)
Remote
router
(spoke)
10.1.1.0/24
46096
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
46095