From: Fred Ingham (fningham@xxxxxxxxxxxxxxxx)
Date: Fri Dec 08 2000 - 03:21:05 GMT-3
To have this work you would have to redistribute rip subnets into ospf
since summary-address is for external routes only. If you look at the
routing table you will see the summary-address command generates the
same 128.1.35.0 /24 to null 0. It does work.
The config is
router ospf 1
summary-address 128.103.35.0 255.255.255.0
redistribute rip subnets
network 128.103.35.0 0.0.0.255 area 0
router rip
redistribute ospf 1 metric 3
network 128.103.0.0
Where the RIP domain is 128.103.36.0/24 and the OSPF domain is
128.103.35.0/28.
A simplier way for this example is to use the default-information
originate under RIP:
The config is:
router ospf 1
redistribute rip subnets
network 128.103.35.0 0.0.0.255 area 0
router rip
network 128.103.0.0
default-information originate
This doesn't work for IGRP.
Cheers, Fred.
"Connary, Julie Ann" wrote:
>
> Hi All,
>
> I have noticed in the tech tips when redistributing between classfull and
> classless protocols
> it uses static routes to null 0 to overcome different subnet mask lengths.
>
> http://www.cisco.com/warp/public/105/52.html
>
> Changing the subnet mask of the OSPF domain is difficult, so instead add a
> static route in Router GW-2 that points to the OSPF domain with a mask of
> 255.255.255.0,
> but with a next hop of null0. Then, redistribute static routes into RIP.
> Here's how to do it:
>
> ip route 128.103.35.0 255.255.255.0 null0
> router rip
> redistribute static
> default metric 1
>
> This allows 128.103.35.0 to be advertised through RIP out the E2/0
> interface of Router GW-2. However, Router GW-2 still has more specific
> routes learned from OSPF
> in its routing table, so the best routing decisions will be made.
>
> My question is, if the OSPF routes are more specific like in the first
> example shown above (i.e. longer subnet masks) than say the
> RIP routes is it valid to use a summary-address in the OSPF ASBR vs. a
> static route to null 0?
>
> The config for the example might be:
>
> router ospf 1
> network 128.103.35.0 0.0.0.255 area 0
> summary-address 128.103.35.0 255.255.255.0
>
> router rip
> network 128.103.0.0
> redistribute ospf metric 1
>
> Julie Ann
>
> ------------------------------------------------------------------------
> Julie Ann Connary
> | | Network Consulting Engineer
> ||| ||| Federal Support Program
> .|||||. .|||||. 13635 Dulles Technology Drive,
> Herndon VA 20171
> .:|||||||||:.:|||||||||:. Pager: 1-888-642-0551
> c i s c o S y s t e m s Email: jconnary@cisco.com
>
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