From: Darren Ward (dward@xxxxxxxxxx)
Date: Mon Apr 16 2001 - 03:23:29 GMT-3
Well i've done some IGRP transaction debugging and found that the originating
router is not advertising the redistributed route for the connected interface
172.16.0.1/24
The command I've used is simply:
!
router igrp 1
redistribute connected metric 1000 10 255 1 1500
network 172.16.0.0
passive-interface serial0/0.1
!
Interface s0/0.1 is the interface with 172.16.0.1/24 on it.
Anyone see anything wrong?
Darren
Lachlan Kidd wrote:
> Hi Darren,
> Can you send a picture with adressing of links etc.
> What you are saying is correct. IGRP sends the following type of routes
> a) classfull routes if the network being advertised is not configured on the
> advertising router.
> b) networks that match the mask of the advertising interface if the route
> and interface belong in the same classfull network.
> My inital guess is you've got
> 'no ip subnet-zero'
> on the router rx'ing the routes (or a version of IOS where this is
> default).
> I've just done some tests on this and found the following
> R3-----R1
> R1 has got a a number of interfaces from the 1.0.0.0 network, all with
> varying masks. The link betwen R1 and R3 is 1.3.1.2/30. Both are running
> IGRP. R1 has a loopback (1.5.1.0/30) also subnetted to /30 and that route
> appears in R3's table. Cool.
> Now...it gets a little strange...
> I configured 'no ip subnet-zero' on R3, and a loopback on R1 with an address
> of 1.0.0.0/30.
> R3 gets the update with both routes (according to debug), but only the
> original 1.5.1.0/30 route is put into the table. That's still fine.
> Put 'ip subnet-zero' onto r3 and both /30 routes appear. Again, as expected.
> Finally...re-applied 'no ip subnet-zero' to R3. Both routes still in table.
> I would have expected that the 1.0.0.0/30 route would have been aged
> out..but next update it got refreshed.
> When I clear ip route * the route goes away and does not come back, but once
> it made it into the table, IGRP kept on updating it. Weird
> Anyone with any comments.
> Lachlan
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
> Darren Ward
> Sent: Monday, 16 April 2001 2:20:PM
> To: ccielab@groupstudy.com
> Subject: IGRP Question
>
> Hi Guys,
>
> A simple one I'm sure but I don't know the answer without default or
> static routes etc....
>
> Consider a network using 172.16.0.0/16 split into all /24's
>
> 172.16.0.0/24 and 172.16.1.0/24 are configured on interfaces on an edge
> router and the
> command 'redistribute connected metric blah blah' is in the IGRP
> process.
>
> Now on the remote IGRP routers all i see is 172.16.1.0/24 i do not see
> 172.16.0.0
>
> Is this because IGRP assumes any route for 172.16.0.0 is the classful
> /16 route since there is no subnet mask info in IGRP and ignores it
> because it does not match the /24 mask required?
>
> Bit confused about this one as I thought as long as i used a /24 mask on
> 172.16.0.0 it should still redistribute.
>
> What's a workaround for this?
>
> Darren
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