From: Chua, Parry (Parry.Chua@xxxxxxxxxx)
Date: Tue Feb 19 2002 - 03:09:33 GMT-3
I do a test on how IGRP routing protocol on update receive from it
neigh.
In one router, all interfaces using mask /24 and the other router using
mask /28 on
the same clasful address.
lo's[/24]---R5[.5]-172.172.58.0/24===172.172.58.0/28[.8]R8--lo's[/28]
eg at R5, 172.172.5.0/24, 172.172.15.0/24, 172.172.58.0/24(address is
.5)
R8, 172.172.8.0/28, 172.172.18.0/28, 172.172.58.0/28(address is
.8)
172.172.8.16/28,172.172.18.16/28
The direct connected network again one side is /28 and the other side is
/24 and sure
that address assign is within the /28 subnet.
Results :-
At mask /28 router
- All the routes from /24 router
At mask /24 router
- Only routes that match /24 in routing table, a debug ip igrp tr show
that all /28
routes has receive at direct connected interface.(ie 172.172.8.16 and
172.172.18.16
are drop)
>From the above, I assume that at each router, based on it interface mask
to determine
the routes it receive, as long as it match to the mask, it treat it
valid and install
in routing table and adverise to the other interfaces accordingly.
Parry Chua
-----Original Message-----
From: yakout esmat [mailto:yesmat@iprimus.com.au]
Sent: Tuesday, February 19, 2002 11:50 AM
To: Chua, Parry; Carolyn Camarda; Brett Lewis; ccielab@groupstudy.com
Subject: RE: IGRP and /32 mask loopback
Right. But the way I look at it is, the receiving and sending interfaces
are
supposed to be in the same network (/30), so if the loopback is not /30
as
well, the sending router will not send it at all.
I might have it all wrong.
-----Original Message-----
From: Chua, Parry [mailto:Parry.Chua@compaq.com]
Sent: Tuesday, February 19, 2002 2:40 PM
To: yakout esmat; Carolyn Camarda; Brett Lewis; ccielab@groupstudy.com
Subject: RE: IGRP and /32 mask loopback
I think what it mean is that, presume the receiving interface mask is
/30, if the receiving
update of the last two bits is not 00, then it is a host route and will
apply a /32 mask,
right ?
Parry Chua
-----Original Message-----
From: yakout esmat [mailto:yesmat@iprimus.com.au]
Sent: Tuesday, February 19, 2002 11:16 AM
To: Carolyn Camarda; Brett Lewis; ccielab@groupstudy.com
Subject: RE: IGRP and /32 mask loopback
I read this article before, and that's what's puzzling me.
Based on the "Sending Updates" section of this article, IGRP router will
not
send-out updates to another IGRP router containing /32 host subnets,
because
it will compare the loopback mask against its source interface mask (In
this
case the serial intf), and if they are not identical (which they are not
of
course) then it will drop the host network and will not advertise it.
THEN when you read the other section "Receiving Updates", """If the
answer
is Yes then Router 2 applies the mask of the interface that received the
update. If the advertised network has a host bit set in the host portion
of
the update, Router 2 applies the host mask (/32). In the case of RIP, it
continues to advertise the /32 route to the subsequent router, but IGRP
doesn't."""
There is a conflict here, How can Router2 receive a network with a bit
set
in the host portion (this contradists the Sending Rule)
Still confusing...
Yakout
-----Original Message-----
From: Carolyn Camarda [mailto:ccamarda@bellsouth.net]
Sent: Tuesday, February 19, 2002 2:02 PM
To: yakout esmat; Brett Lewis; ccielab@groupstudy.com
Subject: Re: IGRP and /32 mask loopback
Check the archives...
http://www.cisco.com/warp/public/105/54.html
IGRP understands it, accepts it, but won't advertise it.
----- Original Message -----
From: "yakout esmat" <yesmat@iprimus.com.au>
To: "Brett Lewis" <blewis@3net-uk.com>
Cc: <ccielab@groupstudy.com>
Sent: Monday, February 18, 2002 8:17 PM
Subject: RE: IGRP and /32 mask loopback
> It is basic config, nothing special. RIP surely understands host
networks
>
>
>
> -----Original Message-----
> From: Brett Lewis [mailto:blewis@3net-uk.com]
> Sent: Tuesday, February 19, 2002 1:28 AM
> To: yakout esmat
> Subject: Re: IGRP and /32 mask loopback
>
>
> I could not get RIP V1 to accept a /32 mask on a loopback. Can you
send me
> your config.
>
>
> Many Thanks
> Brett
> ----- Original Message -----
> From: "yakout esmat" <yesmat@iprimus.com.au>
> To: <ccielab@groupstudy.com>
> Cc: <nobody@groupstudy.com>
> Sent: Monday, February 18, 2002 10:53 AM
> Subject: IGRP and /32 mask loopback
>
>
> > Hi all,
> >
> > I have a problem advertising host addresses of loopbacks (with /32
mask)
> > under IGRP. I don't have this problem with RIP V1.0.
> >
> > Does IGRP understand host networks like RIP? or it behaves
differently ?
> >
> > Appreciate your input.
> >
> > Cheers
> >
> > Yakout
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