PPP bouncing

[bw3481]

I have what I believe is a strange problem. I have a 7507 connecting via T1 to a third party router running ppp. Every 30 minutes the interface goes down for a few seconds, the cpu utilization on the 7507 goes to 100% as OSPF recalculates. I am trying to determine who is causing the link to bounce. I ran a debug of ppp packet and I have inlcuded a small snap shot for when the problem is occuring. As you can see the packet type changes from 0xC021 to 0x0021 and the datagram size skyrockets. Does anyone know what the packet type means or where I can find a document about it.

Jul 26 09:21:44 edt: Se5/5 PPP: I pkt type 0xC021, datagramsize 16

Jul 26 09:21:44 edt: Se5/5 LCP: I ECHOREQ [Open] id 200 len 12 magic 0x61B9997D

Jul 26 09:21:44 edt: Se5/5 LCP: O ECHOREP [Open] id 200 len 12 magic 0xCC114658

Jul 26 09:21:45 edt: Se5/5 PPP: I pkt type 0x0021, datagramsize 72

Jul 26 09:21:45 edt: Se5/5 PPP: O pkt type 0x0021, datagramsize 72

Jul 26 09:21:45 edt: Se5/5 PPP: I pkt type 0xC021, datagramsize 16

Jul 26 09:21:45 edt: Se5/5 LCP: I ECHOREQ [Open] id 201 len 12 magic 0x61B9997D

Jul 26 09:21:45 edt: Se5/5 LCP: O ECHOREP [Open] id 201 len 12 magic 0xCC114658

Jul 26 09:21:46 edt: Se5/5 PPP: I pkt type 0xC021, datagramsize 16

Jul 26 09:21:46 edt: Se5/5 LCP: I ECHOREQ [Open] id 202 len 12 magic 0x61B9997D

Jul 26 09:21:46 edt: Se5/5 LCP: O ECHOREP [Open] id 202 len 12 magic 0xCC114658

Jul 26 09:21:47 edt: Se5/5 PPP: O pkt type 0x0021, datagramsize 1480

Jul 26 09:21:47 edt: Se5/5 PPP: O pkt type 0x0021, datagramsize 1480

Jul 26 09:21:47 edt: Se5/5 PPP: O pkt type 0x0021, datagramsize 1480

thanks in advance.

[Richard Burts]

According to the IANA protocol registry the PPP packet type 0xC021 represents Link Control Protocol and packet type 0x0021 represents an IPv4 packet. So I believe that what you are seeing is a combination of link layer control (keepalive) and real data packets on the line. So far not enough to identify what is the problem.

I would make a suggestion that perhaps you might run debug ppp authentication and or debug ppp negotiation and see if either of them show unusual activity.

One thought is that the connection might be dropping because of missed keepalive packets. Can you tell whether there are many packet drops on the interface?

The URL for the IANA PPP packet type list is:

http://www.iana.org/assignments/ppp-numbers

HTH

Rick

[Harold Ritter]

I have come across some PPP issues between Cisco and Juniper before (I assume this is the 3rd party we are talking about).

Could you let me know what level of code you are running on both the 7500 an the JNPR box.

Thanks,

[bw3481]

Actually this is a Allied Telesyn box.

[Harold Ritter]

I was wrong again ;o) It might help if you were able to capture the ppp trace just before the link protocol goes down.

Thanks,