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Dropped packets on cisco 2901 router

robert.mcclain
Level 1
Level 1

Seeing a lot of dropped packets on my Serial interface. This is a single point to point T1.The outgoing line is not being over utilized. I see the issue is with the buffer, as they equal the number of dropped packets. Is it possible to increase memory on this router to increase buffer space for these packets?

Running c2900-universalk9-mz.SPA.151-2.T5 code.

sh int s0/0/0:0
Serial0/0/0:0 is up, line protocol is up
  Hardware is DSX1
  Description: MGBK1WR70001
  Internet address is 10.221.254.245/24
  MTU 1500 bytes, BW 1544 Kbit/sec, DLY 20000 usec,
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation HDLC, crc 16, loopback not set
  Keepalive set (10 sec)
  Last input 00:00:08, output 00:00:02, output hang never
  Last clearing of "show interface" counters 2d01h
  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 6967
  Queueing strategy: weighted fair
  Output queue: 0/1000/64/6967 (size/max total/threshold/drops)
     Conversations  0/44/256 (active/max active/max total)
     Reserved Conversations 0/0 (allocated/max allocated)
     Available Bandwidth 1158 kilobits/sec
  1 minute input rate 3000 bits/sec, 1 packets/sec
  1 minute output rate 4000 bits/sec, 1 packets/sec
     765505 packets input, 258750698 bytes, 6967 no buffer
     Received 17798 broadcasts (0 IP multicasts)
     0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
     800062 packets output, 310933109 bytes, 0 underruns
     0 output errors, 0 collisions, 0 interface resets
     0 unknown protocol drops
     0 output buffer failures, 0 output buffers swapped out
     0 carrier transitions

Configuration:

interface Serial0/0/0:0
 description MGBK1WR70001
 bandwidth 1544
 ip address X.X.X.X
 no ip redirects
 no ip unreachables
 no ip proxy-arp
 ip flow ingress
 ip traffic-export apply r04 size 10000000
 load-interval 60
 fair-queue
 no cdp enable

 

1 Accepted Solution

Accepted Solutions

Reza Sharifi
Hall of Fame
Hall of Fame

For testing, can you delete these commands:

ip traffic-export apply r04 size 10000000

 fair-queue

than clear the counters and monitor again for packet drops?

HTH

View solution in original post

5 Replies 5

Reza Sharifi
Hall of Fame
Hall of Fame

For testing, can you delete these commands:

ip traffic-export apply r04 size 10000000

 fair-queue

than clear the counters and monitor again for packet drops?

HTH

I just added the fair-queue statement and haven't seen a dropped packet yet. The export command was added to try and alleviate the issue previously. Are you looking for a different error by removing these 2 commands? I can assure you it will be the same.

Still dropping packets after removing the 2 lines stated above.

GHSBEA1-R04#sh int s0/0/0:0
Serial0/0/0:0 is up, line protocol is up
  Hardware is DSX1
  Description: MGBK1WR70001
  Internet address is 10.221.254.245/24
  MTU 1500 bytes, BW 1544 Kbit/sec, DLY 20000 usec,
     reliability 255/255, txload 4/255, rxload 3/255
  Encapsulation HDLC, crc 16, loopback not set
  Keepalive set (10 sec)
  Last input 00:00:06, output 00:00:00, output hang never
  Last clearing of "show interface" counters 6d20h
  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 20950
  Queueing strategy: weighted fair
  Output queue: 0/1000/64/20950 (size/max total/threshold/drops)
     Conversations  0/5/256 (active/max active/max total)
     Reserved Conversations 0/0 (allocated/max allocated)
     Available Bandwidth 1158 kilobits/sec
  1 minute input rate 23000 bits/sec, 10 packets/sec
  1 minute output rate 28000 bits/sec, 11 packets/sec
     1418269 packets input, 561315415 bytes, 20950 no buffer
     Received 58840 broadcasts (0 IP multicasts)
     0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
     1457808 packets output, 634520576 bytes, 0 underruns
     0 output errors, 0 collisions, 0 interface resets
     0 unknown protocol drops
     0 output buffer failures, 0 output buffers swapped out
     0 carrier transitions

 

Do I need more memory on this router or just a more robust router? Seems the traffic is very bursty, it trickles in most of the time and then ti has a large surge and packets get dropped.

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Posting

The issue might be mitigate with buffer tuning.  What do you buffer stats look like?

(BTW, don't know if it applies to 15.x code, but there's also a buffer auto tune option.)

We did run the auto-tuning on the switch.

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