From: Joe (joe.clyde@utah.edu)
Date: Fri Nov 14 2008 - 17:29:29 ARST
Ya, this is what I have seen. Again, at what point is the route NOT specific
enough for the static to disappear and is that something you can configure?
On 11/14/08 11:02 AM, "Hyunseog Ryu" <r.hyunseog@ieee.org> wrote:
> We had this issue in the past.
> If int X fails, 11.11.11.0/24 will still exist in routing table because
> of recursive lookup.
>
> That's why you have to use interface name instead of next-hop IP address
> if possible.
>
>
>
> Joe wrote:
>> I have a question on recursive lookups, hopefully I can phrase it in a way
>> that makes sense. Thanks
>>
>> If I have a static route like:
>> Ip route 11.11.11.0 255.255.255.0 10.10.10.1
>>
>> And I have a route table that looks something like this:
>> C 10.10.10.0/24 via int X
>> O 10.10.0.0/16 via x.x.x.x
>> E 10.0.0.0/8 via x.x.x.x
>> B 0.0.0.0
>>
>> Hopefully you get the idea of the route table...doesn't matter how the
>> routes are learned... just the idea of multiple routes (each less specific).
>>
>> What happens when I lose my directly connected interface? How "un-specific"
>> of a route will the router use for a recursive lookup? *I know in this
>> example if I lost the /24 then the next most specific /16 in this case is
>> next in line but at what point will the router say it won't use a valid
>> route (as far as the route table) for a recursive lookup?
>>
>> I don't believe it will ever use a default route but it seems like I've seen
>> it try to recurse off a /14 route. In my opinion that is an undesirable
>> behavior (let's say you have a summary address to null 0, you wouldn't want
>> you statics still showing up as accessible because the next hop is reachable
>> via a /16 net lets say). I know, I can avoid that issue by adding a specific
>> interface to the static route, but would still like to know at what point do
>> I not do a recursive lookup. Thanks for the help
>>
>>
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-- Joe Clyde Network Engineer Utah Education Network jclyde@uen.org 801-883-4868 (Desk)Blogs and organic groups at http://www.ccie.net
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