From: Chua, Parry (Parry.Chua@xxxxxxxxxx)
Date: Fri Jan 11 2002 - 04:54:24 GMT-3
First of all, a classful summary route to null, this is to terminate
packet destination
for the same classful address but no best path. In eigrp, if auto
summary is on, it will generate the summary route for those route it
advertise. This may not desire, so you can
turn it off and do selected summarization. This allow the flexibility
and you have the control.
Regards
parry
-----Original Message-----
From: Rajeev Siddappa [mailto:raj_lab@yahoo.com]
Sent: Friday, January 11, 2002 3:36 PM
To: Frank B; 'CCIE Lab'
Cc: 'ccielab'; 'j killion'; 'Steven'
Subject: RE: eigrp auto-summary and a null 0 route
Frank, I understand.
Pls see below,
> > Auto-summarization only takes place when you cross
> > classful boundaries.
We are not crossing any classful boundaries here.
We are still in the same router.
> > 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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