[c-nsp] frame errors on ultilink interfaces?

[Jon Lewis]

Is this just another case of "cisco can't count"?  I's seeing input frame 
errors on every multilink interface of a 7206 (12.3(23)) increment about 
the number of input packets the multilink interface is receiving.  In some 
cases, as the interfaces below, there are some errors on the physical 
T1's, but nothing approaching the number or rate of errors seen on the 
multilink interface.  In each case, the input frame errors on the 
multilink interface is actually just a hair below the total input packets.

i.e.

#sh int mu1 | inc packets\ input|input\ errors
      1390839525 packets input, 1498691471 bytes, 0 no buffer
      1390833616 input errors, 0 CRC, 1390833616 frame, 0 overrun, 0 ignored, 0 abort
#sh int mu2 | inc packets\ input|input\ errors
      1401092404 packets input, 3736202100 bytes, 0 no buffer
      1401091942 input errors, 0 CRC, 1401091942 frame, 0 overrun, 0 ignored, 0 abort
#sh int mu3 | inc packets\ input|input\ errors
      1496282 packets input, 536685284 bytes, 0 no buffer
      1495993 input errors, 0 CRC, 1495993 frame, 0 overrun, 0 ignored, 0 abort

Multilink3 is up, line protocol is up
   Hardware is multilink group interface
   Internet address is ...
   MTU 1500 bytes, BW 3072 Kbit, DLY 100000 usec,
      reliability 139/255, txload 33/255, rxload 3/255
   Encapsulation PPP, LCP Open, multilink Open
   Open: IPCP, loopback not set
   Keepalive set (10 sec)
   DTR is pulsed for 2 seconds on reset
   Last input 01:53:57, output never, output hang never
   Last clearing of "show interface" counters 07:47:03
   Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 81
   Queueing strategy: fifo
   Output queue: 0/40 (size/max)
   30 second input rate 42000 bits/sec, 48 packets/sec
   30 second output rate 404000 bits/sec, 55 packets/sec
      1461669 packets input, 525052340 bytes, 0 no buffer
      Received 0 broadcasts, 0 runts, 0 giants, 0 throttles
      1461380 input errors, 0 CRC, 1461380 frame, 0 overrun, 0 ignored, 0 abort
      1599129 packets output, 932362894 bytes, 0 underruns
      0 output errors, 0 collisions, 3 interface resets
      0 output buffer failures, 0 output buffers swapped out
      0 carrier transitions

Serial6/0/7:0 is up, line protocol is up
   Hardware is PA-MC-T3
   MTU 1500 bytes, BW 1536 Kbit, DLY 20000 usec,
      reliability 255/255, txload 17/255, rxload 4/255
   Encapsulation PPP, LCP Open, multilink Open, crc 16, loopback not set
   Keepalive set (10 sec)
   Last input 00:00:00, output 00:00:00, output hang never
   Last clearing of "show interface" counters 07:53:13
   Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 43
   Queueing strategy: fifo
   Output queue: 0/40 (size/max)
   30 second input rate 30000 bits/sec, 20 packets/sec
   30 second output rate 104000 bits/sec, 16 packets/sec
      748831 packets input, 270946224 bytes, 0 no buffer
      Received 0 broadcasts, 0 runts, 0 giants, 0 throttles
      8 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 8 abort
      818879 packets output, 480786728 bytes, 0 underruns
      0 output errors, 0 collisions, 0 interface resets
      0 output buffer failures, 0 output buffers swapped out
      0 carrier transitions no alarm present
   Timeslot(s) Used: 1-24, subrate: 1536Kb/s, transmit delay is 0 flags
   non-inverted data

Serial6/0/17:0 is up, line protocol is up
   Hardware is PA-MC-T3
   MTU 1500 bytes, BW 1536 Kbit, DLY 20000 usec,
      reliability 255/255, txload 22/255, rxload 4/255
   Encapsulation PPP, LCP Open, multilink Open, crc 16, loopback not set
   Keepalive set (10 sec)
   Last input 00:00:00, output 00:00:00, output hang never
   Last clearing of "show interface" counters 07:39:49
   Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 40
   Queueing strategy: fifo
   Output queue: 0/40 (size/max)
   30 second input rate 25000 bits/sec, 20 packets/sec
   30 second output rate 136000 bits/sec, 22 packets/sec
      724957 packets input, 263163858 bytes, 0 no buffer
      Received 0 broadcasts, 0 runts, 0 giants, 0 throttles
      1202 input errors, 42 CRC, 520 frame, 0 overrun, 0 ignored, 640 abort
      791304 packets output, 464004519 bytes, 0 underruns
      0 output errors, 0 collisions, 0 interface resets
      0 output buffer failures, 0 output buffers swapped out
      0 carrier transitions no alarm present
   Timeslot(s) Used: 1-24, subrate: 1536Kb/s, transmit delay is 0 flags
   non-inverted data

interface Multilink3
  ip address ...
  load-interval 30
  no cdp enable
  ppp authorization noauth
  ppp multilink
  ppp multilink fragment disable
  ppp multilink group 3

interface Serial6/0/7:0
  no ip address
  encapsulation ppp
  load-interval 30
  no fair-queue
  no cdp enable
  ppp authorization noauth
  ppp multilink
  ppp multilink group 3

interface Serial6/0/17:0
  no ip address
  encapsulation ppp
  load-interval 30
  no fair-queue
  no cdp enable
  ppp authorization noauth
  ppp multilink
  ppp multilink group 3

----------------------------------------------------------------------
  Jon Lewis                   |  I route
  Senior Network Engineer     |  therefore you are
  Atlantic Net                |
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