Adjustment Of Hello Interval And Hold Time For An Eigrp Process; Stub Routing For An Eigrp Process - Cisco ASR 9000 Series Configuration Manual

Adjustment of Hello Interval and Hold Time for an EIGRP Process

Adjustment of Hello Interval and Hold Time for an EIGRP Process
You can adjust the interval between hello packets and the hold time.
Routing devices periodically send hello packets to each other to dynamically learn of other routers on their
directly attached networks. This information is used to discover neighbors and learn when neighbors become
unreachable or inoperative. By default, hello packets are sent every 5 seconds.
You can configure the hold time on a specified interface for a particular EIGRP routing process designated
by the autonomous system number. The hold time is advertised in hello packets and indicates to neighbors
the length of time they should consider the sender valid. The default hold time is three times the hello interval,
or 15 seconds.

Stub Routing for an EIGRP Process

The EIGRP Stub Routing feature improves network stability, reduces resource usage, 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 in which the distribution router is directly connected to a WAN. The
distribution router can be connected to many more remote routers. Often, the distribution router is 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 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 sends 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 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.
This figure shows a simple hub-and-spoke configuration.
Cisco ASR 9000 Series Aggregation Services Router Routing Configuration Guide, Release 5.1.x
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Implementing EIGRP
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