[j-nsp] Checking for Do Not Age bit on OSPF external LSAs?

Adam Vitkovsky Adam.Vitkovsky at gamma.co.uk
Thu Mar 31 08:20:49 EDT 2016

Hi Chris,
> Of Chris Woodfield
> Sent: Wednesday, March 30, 2016 5:37 PM
> Hi,
> I’m troubleshooting an issue where we’re seeing LSAs for OSPF external
> routes that, in theory, should be getting sent with flood-reduction enabled
> (i.e. should have DoNotAge bit set), but are expiring due to maximum-age.
> Obviously, something’s funky going on…
What do you mean in theory, do you see the flood-reduction being enabled on the ASBR originating this LSA please?

> Here’s an example of a default route being redist’ed into OSPF by our edge
> and received on an adjacent downstream router:
> Extern          x.x.x.x   0x8000212b   132  0x22 0x2a52  36
>  mask
>  Topology default (ID 0)
>    Type: 1, Metric: 0, Fwd addr:, Tag:  Aging timer 00:57:47
> Installed 00:02:06 ago, expires in 00:57:48, sent 00:02:04 ago  Last changed
> 7w4d 21:43:21 ago, Change count: 1  Standby flood status Idle
> Given the fact that there is an expiration date on the database entry, is it
> safe to assume that this LSA was received without a DoNotAge bit set (i.e. if
> it is set, should I be seeing this value set to “Infinite” or similar)? If not, is
> there a way (short of packet captures) to verify whether or not the
> DoNotAge bit is being sent on an LSA?
Yeah I'd expect something like "expires: never" yet the aging timer is clearly running on this LSA


        Adam Vitkovsky
        IP Engineer

T:      0333 006 5936
E:      Adam.Vitkovsky at gamma.co.uk
W:      www.gamma.co.uk

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