From: Chad Marsh (chad@xxxxxx)
Date: Tue Jan 11 2000 - 13:42:20 GMT-3
The 'ip default-network x.x.x.x' command must specify a CLASSFUL
network, such as 140.10.0.0 or 195.118.12.0.
If you specify a subnetwork, you will just get the static route assigned
as you saw.
In order for it to be flagged as candidate default and/or installed as
the Gateway of last resort, the network must appear as a CLASSFUL entry
in the routing table, not as just a subnet of it.
You can use 'ip default-network' either on an upstream router, to
advertise a default network to downstream IGRP speakers, OR, you can
assign it directly on the router you want the default to appear on, if
you meet the above requirements.
You can spoof a default network into an IGRP domain by assigning a bogus
loopback on your ASBR and advertising it into IGRP, then using 'ip
default-network' to flag it as candidate default. It works fine because
all you want the IGRP routers to do is forward it to the next-hop of
your ASBR, which can then route it to the appropriate destination.
Hope that helps,
Chad Marsh
CCIE# 5185
> "Maljure, Sanjay" wrote:
>
> Hi,
> I tried the "ip default-network X.X.X.X" where X.X.X.X was
> the connected network between R2 and R3. This did not inject
> a default route into R1. A static route appeared in R2
> instead.
> However I later tried "ip default-network Y.Y.Y.Y" where
> Y.Y.Y.Y was a route learned by R2 through OSPF and this did
> inject a default route in to R1.
> The documentation says that this should have worked even in
> the first case (connected network).
> Can anyone else throw some more light on this?
> Thanks
> Sanjay
>
>
>
> Hello All,
>
> I have IGRP redistributing into OSPF just fine. VLSM <-->
> FLSM. Now I want to distribute a default route into my IGRP
> domain from the ASBR as follows:
>
> R1------------R2---------R3--------R4
>
> |---IGRP-----|-----------OSPF------|
>
> At R2, I am trying to add the "ip default-netowrk X.X.X.X"
> command and the external route is not being forwarded to R1.
> Can you help?
>
> Thanks,
> Ben Rife
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