Hub and Spoke

The Enhanced Interior Gateway Routing Protocol (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 router responds to

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.

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