Cisco Systems 78-11741-02 Wireless Office Headset User Manual


 
Configuring EIGRP
EIGRP Configuration Task List
IPC-271
Cisco IOS IP Configuration Guide
Figure 51 Dual-Homed Remote Topology with a Failed Route to a Distribution Router
It is not desirable for traffic from distribution router 2 to travel through any remote router in order to
reach network 10.3.1.0/24. If the links are sized to handle the load, it would be acceptable to use one of
the backup routes. However, most networks of this type have remote routers located at remote offices
with relatively slow links. This problem can be prevented if proper summarization is configured on the
distribution router and remote router.
It is typically undesirable for traffic from a distribution router to use a remote router as a transit path. A
typical connection from a distribution router to a remote router would have much less bandwidth than a
connection at the network core. Attempting to use a remote router with a limited bandwidth connection
as a transit path would generally produce excessive congestion to the remote router. The EIGRP Stub
Routing feature can prevent this problem by preventing the remote router from advertising core routes
back to distribution routers. Routes learned by the remote router from distribution router 1 will not be
advertised to distribution router 2. Since the remote router will not advertise core routes to distribution
router 2, the distribution router will not use the remote router as a transit for traffic destined for the
network core.
The EIGRP Stub Routing feature can help to provide greater network stability. In the event of network
instability, this feature prevents EIGRP queries from being sent over limited bandwidth links to
nontransit routers. Instead, distribution routers to which the stub router is connected answer the query
on behalf of the stub router. This feature greatly reduces the chance of further network instability due to
congested or problematic WAN links. The EIGRP Stub Routing feature also simplifies the configuration
and maintenance of hub-and-spoke networks. When stub routing is enabled in dual-homed remote
configurations, it is no longer necessary to configure filtering on remote routers to prevent those remote
routers from appearing as transit paths to the hub routers.
Caution EIGRP Stub Routing should only be used on stub routers. A stub router is defined as a router
connected to the network core or distribution layer through which core transit traffic should not flow.
A stub router should not have any EIGRP neighbors other than distribution routers. Ignoring this
restriction will cause undesirable behavior.
Note Multi-access interfaces, such as ATM, Ethernet, Frame Relay, ISDN PRI, and X.25, are supported by
the EIGRP Stub Routing feature only when all routers on that interface, except the hub, are
configured as stub routers.
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
X
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