Cisco Catalyst 4500 Series, Руководство по настройке программного обеспечения, Страница: 944 / 2086

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Catalyst 4500 Series Switch, Cisco IOS Software Configuration Guide - Cisco IOS XE 3.9.xE and IOS 15.2(5)Ex
Chapter 35 Configuring Layer 3 Interfaces
Configuring EIGRP Stub Routing
the remote router even if routes are being summarized. If there is a problem communicating over the
WAN link between the distribution router and the remote router, an EIGRP stuck in active (SIA)
condition could occur and cause instability elsewhere in the network. The EIGRP stub routing feature
allows a network administrator to prevent queries from being sent to the remote router.
Dual-Homed Remote Topology
In addition to a simple hub-and-spoke network where a remote router is connected to a single distribution
router, the remote router can be dual-homed to two or more distribution routers. This configuration adds
redundancy and introduces unique issues, and the stub feature helps to address some of these issues.
A dual-homed remote router has two or more distribution (hub) routers. However, the principles of stub
routing are the same as they are with a hub-and-spoke topology.
Figure 35-5 shows a common
dual-homed remote topology with one remote router, but 100 or more routers could be connected on the
same interfaces on distribution router 1 and distribution router 2. The remote router uses the best route
to reach its destination. If distribution router 1 experiences a failure, the remote router can still use
distribution router 2 to reach the corporate network.
Figure 35-5 Simple Dual-Homed Remote Topology
Figure 35-5 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 35-6 , 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).
Corporate
network
Distribution
router 1
(hub)
Distribution
router 2
(hub)
Remote
router
(spoke)
10.1.1.0/24
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