From: Chris McCoy (mccoy-cm@pacbell.net)
Date: Fri Sep 26 2003 - 22:41:35 GMT-3
Ken,
EIGRP stub is designed for massive hub-and-spoke environments, and it
is configured on the spoke. The spoke sets some indicator bits in the
EIGRP hello packets that tells the hub it is a stub. The idea is, the
spoke will only advertise what routes are directly connected,
redistributed, or summarized, depending on how it is configured
respectively. By the same token, the hub will not query the spoke for
alternate routes to other networks the spoke has nothing to do with. It
works great with frame relay or other networks with very little
bandwidth available for your routing protocol. Network engineers with
very large networks had many problems with Stuck in Actives (SIAs)
events happening because of EIGRP query messages for networks elsewhere
getting lost to their spokes. Unfortunately, the way EIGRP is designed,
even if you are only sending the default route (0.0.0.0/0) to the spoke
using the ip summary-address command, the hub will still send queries
that are more specific than the default when some network goes down.
The spoke is supposed to answer back right away saying it doesn't have
an alternate path, but this exchange may get lost. The stub feature
helps tremendously with these kind of networks and its operation makes a
lot of sense. Why would a hub query a spoke for a network, when there
is no way the spoke has an alternate route? As you have also
discovered, EIGRP stub is an easy way to keep your router from becoming
a transit router for traffic not directly going to an interface
connected.
Chris McCoy, #11801
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Ken.Farrington@barclayscapital.com
Sent: Thursday, September 25, 2003 2:48 AM
To: ccielab@groupstudy.com
Subject: EIGRP Stub Feature
Another Quick One :)
+----+
+------------| R1 |-------------+
| +----+ |
| eigrp |
+----+ stub +----+ loopback0 141.228.2.1
| R2 | | R3 |----------------
+----+ +----+
|
|
|loopback0 141.228.11.1
eigrp 1
network 192.168.0.0
no auto-summ
With eigrp stub routing enabled,
R1 will not advertise 141.228.11.1 to R3
R1 will not advertise 141.228.2.1 to R2
Is this how stub routing is ment to work and if so, can you tell me why?
It makes sense really. There is limited docs on this feature, and just
want to read something that says "this is what should happen"
Many thx
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