From: Frank B (frank@xxxxxxxxxxxx)
Date: Fri Jan 11 2002 - 02:59:13 GMT-3
Auto-summarization only takes place when you cross classful boundaries.
You have 2 interfaces connected within the 168.71.0.0 space; so it sends
advertisements out those interfaces for subnets within 168.71.0.0
However, other networks advertised out those interfaces are summarized
on their classful boundary. Hope this helps.
Frank
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
CCIE Lab
Sent: Thursday, January 10, 2002 7:34 PM
To: j killion; Steven; ccielab
Subject: Re: eigrp auto-summary and a null 0 route
good, but why didn't it also create a summary route to
null for 168.71.0.0 subnets?
--- j killion <jkillion1977@yahoo.com> wrote:
> Once you added the "auto-summary" cmd, EIGRP will
> now
> summarize at network boundaries - in this case at
> 20.0.0.0/8. It creates the summary pointing to
> Null0
> to stop routing loops from forming.
>
>
> --- Steven <adream@163.com> wrote:
> > On one router which runs eigrp only ,the config
> and
> > route table is as follows,
> >
> > sh run
> > ...
> > router eigrp 1
> > network 20.0.0.0
> > network 168.71.7.0 0.0.0.255
> > network 168.71.9.0 0.0.0.255
> > no auto-summary
> > no eigrp log-neighbor-changes
> >
> > ...
> >
> > 168.71.0.0/24 is subnetted, 4 subnets
> > C 168.71.9.0 is directly connected, Serial1
> > C 168.71.7.0 is directly connected, Serial0
> > D 168.71.6.0 [90/20768000] via 168.71.9.1,
> > 00:00:17, Serial1
> > D 168.71.5.0 [90/20384000] via 168.71.9.1,
> > 00:00:17, Serial1
> > 20.0.0.0/24 is subnetted, 1 subnets
> > C 20.1.1.0 is directly connected, Loopback0
> >
> >
> > after i add "auto-summary "command under router
> > eigrp 1
> >
> > the route table change to the following one ,
> >
> > 168.71.0.0/24 is subnetted, 4 subnets
> > C 168.71.9.0 is directly connected, Serial1
> > C 168.71.7.0 is directly connected, Serial0
> > D 168.71.6.0 [90/20768000] via 168.71.9.1,
> > 00:00:03, Serial1
> > D 168.71.5.0 [90/20384000] via 168.71.9.1,
> > 00:00:03, Serial1
> > 20.0.0.0/8 is variably subnetted, 2 subnets,
> 2
> > masks
> > D 20.0.0.0/8 is a summary, 00:00:01, Null0
> > C 20.1.1.0/24 is directly connected,
> Loopback0
> >
> >
> > i just want to know what "D 20.0.0.0/8 is a
> > summary, 00:00:01, Null0"
> > mean.Why is it added?
> >
> >
> >
> > Thanks.
> >
>
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