[c-nsp] T3 circuit drops for 10 seconds and then returns

[Devon True]

All:

I am helping to troubleshoot a T3 circuit that keeps dropping. It loses 
line protocol, goes down for 10 seconds, and then comes back up. I did a 
"debug serial interface" and got the following when the T3 dropped.

The carrier has tested the circuit several times and the PA-T3 card has 
been replaced. Anyone have any ideas?

---- show log snippet ----

Jun  3 16:00:18.841 EDT: Serial2/0: HDLC myseq 347, mineseen 347*, 
yourseen 347, line up
Jun  3 16:00:28.841 EDT: Serial2/0: HDLC myseq 348, mineseen 348*, 
yourseen 348, line up
Jun  3 16:00:38.841 EDT: Serial2/0: HDLC myseq 349, mineseen 349*, 
yourseen 349, line up
Jun  3 16:00:48.841 EDT: Serial2/0: HDLC myseq 350, mineseen 349*, 
yourseen 350, line up
Jun  3 16:00:58.841 EDT: Serial2/0: HDLC myseq 351, mineseen 349*, 
yourseen 351, line up
Jun  3 16:01:08.841 EDT: Serial2/0: HDLC myseq 352, mineseen 349*, 
yourseen 352, line up
Jun  3 16:01:18.841 EDT: Serial2/0: HDLC myseq 353, mineseen 349*, 
yourseen 353, line up
Jun  3 16:01:28.841 EDT: Serial2/0: HDLC myseq 354, mineseen 349*, 
yourseen 354, line up
Jun  3 16:01:38.842 EDT: Serial2/0: HDLC myseq 355, mineseen 349*, 
yourseen 355, line down
Jun  3 16:01:39.842 EDT: %LINEPROTO-5-UPDOWN: Line protocol on Interface 
Serial2/0, changed state to down
Jun  3 16:01:48.842 EDT: Serial2/0: HDLC myseq 356, mineseen 356*, 
yourseen 356, line up
Jun  3 16:01:49.842 EDT: %LINEPROTO-5-UPDOWN: Line protocol on Interface 
Serial2/0, changed state to up
Jun  3 16:01:58.842 EDT: Serial2/0: HDLC myseq 357, mineseen 357*, 
yourseen 357, line up
Jun  3 16:02:08.842 EDT: Serial2/0: HDLC myseq 358, mineseen 358*, 
yourseen 358, line up

------------------------------

---- show version ----

Cisco Internetwork Operating System Software
IOS (tm) 7200 Software (C7200-IS-M), Version 12.0(3)T3,  RELEASE 
SOFTWARE (fc1)
Copyright (c) 1986-1999 by cisco Systems, Inc.
Compiled Fri 16-Apr-99 11:19 by kpma
Image text-base: 0x60008900, data-base: 0x60EB0000

ROM: System Bootstrap, Version 11.1(10) [dschwart 10], RELEASE SOFTWARE 
(fc1)
BOOTFLASH: 7200 Software (C7200-P-M), Version 12.0(28a), RELEASE 
SOFTWARE (fc1)

bell-rtr1 uptime is 1 hour, 0 minutes
System restarted by power-on at 15:02:13 EDT Fri Jun 3 2005
System image file is "slot0:c7200-is-mz.120-3.T3"

cisco 7206 (NPE150) processor with 122880K/8192K bytes of memory.
R4700 CPU at 150Mhz, Implementation 33, Rev 1.0, 512KB L2 Cache
6 slot midplane, Version 1.3

Last reset from power-on
Bridging software.
X.25 software, Version 3.0.0.
1 FastEthernet/IEEE 802.3 interface(s)
1 Serial network interface(s)
125K bytes of non-volatile configuration memory.
1024K bytes of packet SRAM memory.

16384K bytes of Flash PCMCIA card at slot 0 (Sector size 128K).
20480K bytes of Flash PCMCIA card at slot 1 (Sector size 128K).
4096K bytes of Flash internal SIMM (Sector size 256K).
Configuration register is 0x2102

------------------------------

---- show interface ----

Serial2/0 is up, line protocol is up
   Hardware is M1T-T3 pa
   Description:
   Internet address is x.x.x.x/30
   MTU 4470 bytes, BW 44210 Kbit, DLY 200 usec,
      reliablility 255/255, txload 3/255, rxload 10/255
   Encapsulation HDLC, 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 never
   Queueing strategy: fifo
   Output queue 0/40, 54415 drops; input queue 3/75, 5 drops
   5 minute input rate 1844000 bits/sec, 283 packets/sec
   5 minute output rate 586000 bits/sec, 328 packets/sec
      994562 packets input, 846996446 bytes, 0 no buffer
      Received 0 broadcasts, 0 runts, 0 giants, 5 throttles
               0 parity
      0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
      1166824 packets output, 291277842 bytes, 0 underruns
      0 output errors, 0 applique, 13 interface resets
      0 output buffer failures, 0 output buffers swapped out
      15 carrier transitions
    rxLOS inactive, rxLOF inactive, rxAIS inactive
    txAIS inactive, rxRAI inactive, txRAI inactive

------------------------------

Devon