ospf MAXage problem

senthil1976 · ‎04-18-2007

I got a message from two ABR. message says 'Maximum age reached for an LS advertisment'. But there were not any link problems(no NMS loggs). link utilization also very small. I think that there is no possibility that ospf refresh packets would be droped. So what could be the reason for this message.

Regards

Senthil

mounir.mohamed · ‎04-19-2007

Dear senthil,

Each OSPF LSA has an age, which indicates whether the LSA is still valid. Once the LSA reaches the maximum age (one hour), it is discarded. During the aging process, the originating router sends a refresh packet every 30 minutes to refresh the LSA. Refresh packets are sent to keep the LSA from expiring, whether there has been a change in the network topology or not. Checksumming is performed on all LSAs every 10 minutes. The router keeps track of LSAs it generates and LSAs it receives from other routers. The router refreshes LSAs it generated; it ages the LSAs it received from other routers.

for more information kindly check:

http://www.cisco.com/en/US/products/sw/iosswrel/ps1826/products_feature_guide09186a0080087d4d.html

Please rate helpful posts.

Best Regards,

Mounir Mohamed

senthil1976 · ‎04-19-2007

Thanks Mohamad,

Actually I knew the concept of the ospf refresh packets. But in my problem I got an MaxAge reached problem for an LSA. this means there was a drop of ospf refresh packet. But this is to happen there should be a link down or link congestion. But there was no evidance for link down or link congestion. so I am seprise that what could be the reson for drop of ospf refresh packet.

Regards,

Senthil

Harold Ritter · ‎04-19-2007

Senthil,

Is this a multi-vendor network?

Thanks,

Harold Ritter
Sr Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México
Paseo de la Reforma 222
Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México

senthil1976 · ‎04-19-2007

Hi Hritter,

No. It is under administration of single vender. But the both ABR are GSRs.

Thanks,

Senthil

Harold Ritter · ‎04-19-2007

Thanks for the feedback. I had seen a simular issue but it was related to a minor interoperability between Cisco and an other vendor. I guess it doesn't apply to your case then.

Cheers,

Harold Ritter
Sr Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México
Paseo de la Reforma 222
Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México

senthil1976 · ‎04-19-2007

Thanks Hritter.

Hi Guys,

I really need to know that is there any possiblity to drop ospf referesh packet with out any congestion in links? Or what are the possiblities that summary LSA reaches the MaxAge except following reasons,

1) Refresh packet does not received

2) lack of sequence number for ospf process

Regards,

Senthil

CSCO10899265 · ‎04-22-2007

Hi,

Have any of your ospf areas been translated as a stub or NSSA AREA? If so this situation is entirely possible

Nimesh Amin

senthil1976 · ‎04-22-2007

Hi,

There is no stub or NSSA area.

what is the reason to happen this in case Stub or NSSA area is there?

Thanks,

Senthil