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Cisco Catalyst Blade Switch 3020 for HP Software Configuration Guide
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Chapter 34 Configuring IP Unicast Routing
Configuring Stub Routing
Understanding EIGRP Stub Routing
The EIGRP stub routing feature reduces resource utilization by moving routed traffic closer to the end
user. In a network using EIGRP stub routing, the only allowable route for IP traffic to the user is through
a switch that is configured with EIGRP stub routing. The switch sends the routed traffic to interfaces that
are configured as user interfaces or are connected to other devices.
Note
The switch does not support complete EIGRP routing. It contains EIGRP stub routing capability, which
only advertises connected or summary routes from the routing tables to other switches in the network.
The switch uses EIGRP stub routing at the access layer to eliminate the need for other types of routing
advertisements. If you try to configure multi-VRF-CE and EIGRP stub routing at the same time, the
configuration is not allowed.
When using EIGRP stub routing, you need to configure the distribution and remote routers to use EIGRP
and to configure only the switch as a stub. Only specified routes are propagated from the switch. The
switch responds to all queries for summaries, connected routes, and routing updates.
Any neighbor that receives a packet informing it of the stub status does not query the stub router for any
routes, and a router that has a stub peer does not query that peer. The stub router depends on the distribution
router to send the proper updates to all peers.
In
Figure 34-5
, switch B is configured as an EIGRP stub router. Switches A and C are connected to the rest
of the WAN. Switch B advertises connected, static, redistribution, and summary routes to switch A and C.
Switch B does not advertise any routes learned from switch A (and the reverse).
Figure 34-5
EIGRP Stub Router Configuration
When configuring the distribution router to send only a default route to the remote router, you must use
the
ip classless
global configuration command on the remote router. By default, the
ip classless
command is enabled in all Cisco IOS images that support the EIGRP stub routing feature.
Without the stub feature, even after the routes that are sent from the distribution router to the remote
router have been filtered or summarized, a problem might occur. If a route is lost somewhere in the
corporate network, EIGRP could send a query to the distribution router, which in turn will send a query
to the remote router even if routes are being summarized. The EIGRP Stub Routing feature allows a
network administrator to prevent queries from being sent to the remote router.
Host A
Host B
Switch B
Switch A
Routed to WAN
Switch C
Host C
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