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


 
Configuring EIGRP
EIGRP Configuration Task List
IPC-268
Cisco IOS IP Configuration Guide
Configuring EIGRP Stub Routing
The EIGRP Stub Routing feature improves network stability, reduces resource utilization, and simplifies
stub router configuration.
Stub routing is commonly used in a hub-and-spoke network topology. In a hub-and-spoke network, one
or more end (stub) networks are connected to a remote router (the spoke) that is connected to one or more
distribution routers (the hub). The remote router is adjacent only to one or more distribution routers. The
only route for IP traffic to follow into the remote router is through a distribution router. This type of
configuration is commonly used in WAN topologies where the distribution router is directly connected
to a WAN. The distribution router can be connected to many more remote routers. Often, the distribution
router will be connected to 100 or more remote routers. In a hub-and-spoke topology, the remote router
must forward all nonlocal traffic to a distribution router, so it becomes unnecessary for the remote router
to hold a complete routing table. Generally, the distribution router need not send anything more than a
default route to the remote router.
When using the EIGRP Stub Routing feature, you need to configure the distribution and remote routers
to use EIGRP, and to configure only the remote router as a stub. Only specified routes are propagated
from the remote (stub) router. The stub router responds to all queries for summaries, connected routes,
redistributed static routes, external routes, and internal routes with the message “inaccessible.” A router
that is configured as a stub will send a special peer information packet to all neighboring routers to report
its status as a stub router.
Any neighbor that receives a packet informing it of the stub status will not query the stub router for any
routes, and a router that has a stub peer will not query that peer. The stub router will depend on the
distribution router to send the proper updates to all peers.
Figure 48 shows a simple hub-and-spoke configuration.
Figure 48 Simple Hub-and-Spoke Network
The stub routing feature by itself does not prevent routes from being advertised to the remote router. In
the example in Figure 48, the remote router can access the corporate network and the Internet through
the distribution router only. Having a full route table on the remote router, in this example, would serve
no functional purpose because the path to the corporate network and the Internet would always be
through the distribution router. The larger route table would only reduce the amount of memory required
by the remote router. Bandwidth and memory can be conserved by summarizing and filtering routes in
the distribution router. The remote router need not receive routes that have been learned from other
networks because the remote router must send all nonlocal traffic, regardless of destination, to the
distribution router. If a true stub network is desired, the distribution router should be configured to send
Corporate
network
Internet
Remote
router
(spoke)
Distribution
router
(hub)
10.1.1.0/24
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