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

Chris Woodfield rekoil at semihuman.com
Wed Mar 30 12:37:28 EDT 2016


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…

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
 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?



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