7206VXR OC-3 Sonet Output Drops

[smarotta82]

Hello,

I have a point-point Sonet OC-3, both ends terminated by 7206VXR router. The circuit is only operating at about 2/3's capacity (100MB) and i am getting a ton of OutputDrops. I have included the show int for the POS below, the utilization was not high at the time of capture. Has anyone ever seen this before?

POS1/0 is up, line protocol is up

Hardware is Packet over Sonet

Internet address is 192.168.2.1/24

MTU 4470 bytes, BW 155000 Kbit, DLY 100 usec,

reliability 255/255, txload 2/255, rxload 1/255

Encapsulation HDLC, crc 32, loopback not set

Keepalive set (10 sec)

Scramble disabled

Last input 00:00:01, output never, output hang never

Last clearing of "show interface" counters 1d16h

Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 43764

Queueing strategy: random early detection(RED)

30 second input rate 35000 bits/sec, 73 packets/sec

30 second output rate 1482000 bits/sec, 136 packets/sec

245406033 packets input, 2578976581 bytes, 0 no buffer

Received 0 broadcasts, 0 runts, 0 giants, 0 throttles

0 parity

0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort

480392843 packets output, 2355422897 bytes, 0 underruns

0 output errors, 0 applique, 1 interface resets

0 output buffer failures, 0 output buffers swapped out

0 carrier transitions

[paolo bevilacqua]

Which NPE are you using? Proved problems like the one exposed by Calvin Chu tend to happen with certain hardware but not other due to architectural reasons.

[smarotta82]

I am using the NPE-G2 also.

[marikakis]

Hello,

Your issue could be a bug, but it might not be the same as the one already mentioned. That's why I said previously to check with Cisco about a bug as the one mentioned. Some bugs look similar, but they are not exactly the same, which means that another workaround or resolving software might be needed.

The problem with your topology is that you cannot feed the OC3 with enough traffic to see how far the throughput can go even with drops. Unless your 7200 has a gigabit (this is not clear to me, you only mentioned the speed of the backup machines), in which case you could perhaps direct additional traffic towards the OC3 to confirm throughput issues. Up to now your throughput does reach the expected maximum according to the feeding backup machine speed. Up to now I only see "drop issues", which could be a bug or it could not (if for example a significant percentage of the traffic consists of small packets, the small packets might be filling your output queues). Another difference I see is the CPU clue. The previous post that mentioned a bug was talking about seeing "higher processor loading" and does not state how much it was, while you said that you had monitored your CPU during your issue and it was somewhat low (7%).

I hope this will help you in your search for a similar bug and a workaround for your own issue.

Kind Regards,

M.

p.s. If you find a solution to your issue, it would be kind if you reported back to us how your issue was resolved. I finally remember to mention that I find pretty cool the somewhat not usual method you troubleshooted it, by enabling RED on your router.

[calvin.chu]

I think he have enough traffic as he see peak off at 100M. Anyway, NPE-G2 has 3 GE ports on board. So shouldn't have problem to generate some more traffic to the link if topology support.

For the "higher processor loading", I want to mention we have policy-map on the link and BGP,OSPF,etc on the production router. Loading save from 8x% to 6x% after we changed IOS. I can't say which part caused the extra loading. But on the test bed, loading is very low when we confirm the POS throughput issue. These are major issues found in 12.4.11T train. I didn't mean the loading caused the throughput issue.

I also try to search Cisco bug before but didn't get it. May be the keywords I used not correct or just Cisco didn't know it yet. So I report to Cisco but got rejected.

I would suggest to replicate the problem to confirm link or IOS issue if have spare equipment. Or do a quick IOS change on the router as it is backup link. 12.4.4XD10,XD7 and 12.4.15T1 is ok in our test. And tell us the IOS version currently using so I might be able to test here as well.

[smarotta82]

Im running 12.4.4XD7 and will running tests on the circuit this week.

[marikakis]

Hello,

According to Kalvin, the issue he reported is resolved in the IOS version you are running. Nevertheless, Kalvin has shared with us a lot of useful information and I believe you should be rating his post the same way I did.

Kind Regards,

M.

[calvin.chu]

Thanks. One last thing I want to confirm is the feature set of IOS. Are you running Advanced IP Services feature set? If yes, then probably not the same issue as mine.