[quagga-dev 8472] Fwd: Query regarding OSPF

Balaji G balajig81 at gmail.com
Sat Jan 8 02:57:53 GMT 2011


Can some one look at this and let me know the reason for this behavior in
OSPF ?  The scenario is explained in this mail thread.

Thanks for your time.

  - Balaji

---------- Forwarded message ----------
From: Balaji G <balajig81 at gmail.com>
Date: Fri, Jan 7, 2011 at 10:09 PM
Subject: Re: Query regarding OSPF
To: Paul Jakma <paul at jakma.org>, Greg Troxel <gdt at ir.bbn.com>


I went through some ospf books and found out that there is a ageing concept
for each LSA and the max age is 3600 seconds so i was under the impression
that in my case, the LSA would get deleted after 3600 seconds which is the
MAX AGE since i have removed the static route but to my surprise i saw that
even after deleting the route from the RTM using the no ip route command
after the ageing reaches about 1800 and odd seconds i saw that the ageing
again got reset to 0 and started once again, coz i was hoping that the route
which i deleted would get removed from the LSA after 3600 seconds but it
didnt happen.

Can you let me know the reason for this behavior ?

  - Balaji

On Mon, Jan 3, 2011 at 10:28 PM, Balaji G <balajig81 at gmail.com> wrote:

> Hi Paul,Greg
> Wish you a very Happy and Prosperous New Year.
> I have got a query regarding OSPF in general as well as with respect to
> Quagga.  I am running Quagga OSPF in both ends. One end is my host and the
> other end is a qemu instance instance. As you would expect the network
> connectivity happens through the tap0 from the host to eth0 interface inside
> the qemu device to which the IP addresses and with mask 8
> is configured. I create two static routes viz, with nexthop set
> to and an other static route with the same nexthop
> In the OSPF i do a redistribute static of the routes in the host and in the
> remote (VM) end i see 2 entries under when i do show ip ospf external
> routing table.
> Scenario 1: I do a delete of the static route (which is the
> less specific route) of the two but i don't see this route being deleted
> from the OSPF DB. I would like to know the reason for this, is there any
> protocol specific reason as such ?
> Scenario 2: I do a delete of the more specific static route i again don't see the routes being deleted from the OSPF DB. Again would
> like to know the reason for this
> The above test cases with BGP, BGP deletes the route from the RIB
> correspondingly. Hence i would like to know whether its a bug in OSPF as
> such or is this behavior in adherence with the protocol.
> Question 3:  When i do a show ip ospf database in the remote side i see the
> following: Please refer the screenshot attached.
> In the attached screenshot i am not able to see the static route in the
> last column it shows some route which is not been injected at all.
> Thanks for your time.
> Cheers,
>  - Balaji
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