From: Alexander Arsenyev (GU/ETL) (alexander.arsenyev@ericsson.com)
Date: Thu Oct 20 2005 - 09:59:33 GMT-3
It appears that IP subnets belonging to links between the routers would not need to be advertised by the ISIS in order to provide connectivity to loopbacks:
<quote>
The IP internal reachability information entries consist of a 4-octet IP address plus a 4-octet subnet mask and will always be a leaf, that is, "End System" in PATHS.
</quote>
http://www.cisco.com/warp/public/cc/pd/iosw/prodlit/insys_wp.htm , "Link State Database" section.
The way I understand it, only CLNS reachability information is needed to build a SPF tree, then leaves (IP reachability) are added.
HTH
Cheers
Alex
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
De Witt, Duane
Sent: 20 October 2005 13:37
To: Danny Muizebelt; McCallum, Robert; Cisco certification
Subject: RE: ISIS --- advertise passive-only
Hi
I'm understanding that you want your IGP to provide connectivity to the
loopbacks so that BGP can handle all of the edge prefixes? Surely to
provide reachability to the loopbacks the links between the routers
would also need to be advertised by the IGP?
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Danny Muizebelt
Sent: 20 October 2005 02:28 PM
To: McCallum, Robert; Cisco certification
Subject: AW: ISIS --- advertise passive-only
Hi Robert,
If I don't put the "ip router isis" no neighbour relationship is
possible over this interface. But while configuring this neighbour
relationship I also add the connected network/interface to the
link-state database. For a BGP network I only need loopback addresses
and all other internal networks would only clutter up my ISIS table.
For instance, which interfaces are on passive? Loopback and customer
interfaces. Which networks are interesting for BGP? Loopback and
customer networks.
So I think that the "advertise passive-only" option is pretty nifty to
separate the tasks each routing protocol is supposed to do. Too bad they
didn't think sooner of it.
I don't think it's possible to set up a some sort of clns unicast
neighbour statement without using the "ip router isis" command.
-Danny
> -----Urspr|ngliche Nachricht-----
> Von: McCallum, Robert [mailto:robert.mccallum@thus.net]
> Gesendet: Donnerstag, 20. Oktober 2005 14:15
> An: Danny Muizebelt; Cisco certification
> Betreff: RE: ISIS --- advertise passive-only
>
> I must be missing something here but to advertise a connected
> network in
> isis you must place the ip router isis command on the interface. If
> you
> don't want to advertise a certain interface then just don't place
> that
> command on the interface.
>
> Robert McCallum CCIE #8757
>
>
>
> > -----Original Message-----
> > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On
> > Behalf Of Danny Muizebelt
> > Sent: 20 October 2005 12:13
> > To: Cisco certification
> > Subject: ISIS --- advertise passive-only
> >
> > Hi Group,
> >
> > I was looking for a feature in ISIS where I could suppress
> > the networks of connected interfaces toward neighbour ISIS
> > routers. I only wanted the loopback addresses advertised by
> > the IGP so BGP would take care of the rest.
> >
> > It started off very well on my 1841 with 12.4(1a) loaded (There is
> no
> > 12.2T) and what did I find?
> >
> > advertise Control which IP routes flow in L1 and L2 LSPs
> > R8(config-router)#advertise ?
> > passive-only only interface address of passive interfaces
> > R8(config-router)#advertise passive-only ?
> > <cr>
> > R8(config-router)#advertise passive-only
> >
> > And this works like a charm:
> >
> > R8.00-00 0x000000F1 0x71DB 993
> > 0/0/0
> > Auth: Length: 7
> > Area Address: 10
> > NLPID: 0xCC
> > Hostname: R8
> > IP Address: 10.100.100.8
> > Metric: 0 IP 10.100.100.8 255.255.255.255
> > Metric: 10 IS R8.02
> > Metric: 10 IS R8.01
> > R8.01-00 0x000000E9 0xCFD7 1142
> > 0/0/0
> > Auth: Length: 7
> > Metric: 0 IS R8.00
> > Metric: 0 IS R9.00
> >
> > So I was slightly depressed when I discovered that the 12.2T
> > release didn't have this feature or any other possibility to
> > suppress advertised networks.
> >
> > It seems to me that "advertise passive-only" was really
> > implemented for ISIS/BGP or ISIS/MBGP combos for larger ISP
> > backbone networks.
> >
> > Or is there another way of only advertising your loopbacks over
> ISIS?
> >
> > Cheers,
> >
> > Danny
> >
> >
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