10-26-2006 03:07 PM - edited 03-03-2019 02:29 PM
I have 4 T1's configured in an IMA bundle in a 7200 with an IMA PA card. I'm getting CRC errors on the IMA interface. The carrier tested each T1 individually and saw no errors. I also shut each T1 down individually and while each one was down, the errors continued to increment on the IMA interface. This tells me that no single T1 is causing the errors. What else could be causing these errors? Here are some outputs:
ROUTER>sh int atm4/ima0
ATM4/ima0 is up, line protocol is up
Hardware is IMA PA
MTU 4470 bytes, sub MTU 4470, BW 6093 Kbit, DLY 20000 usec,
reliability 255/255, txload 3/255, rxload 11/255
Encapsulation ATM, loopback not set
Encapsulation(s): AAL5
2047 maximum active VCs, 4 current VCCs
VC Auto Creation Disabled.
VC idle disconnect time: 300 seconds
0 carrier transitions
Last input 00:00:00, output 00:00:00, output hang never
Last clearing of "show interface" counters 00:31:50
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: Per VC Queueing
5 minute input rate 279000 bits/sec, 58 packets/sec
5 minute output rate 87000 bits/sec, 58 packets/sec
142955 packets input, 68773978 bytes, 0 no buffer
Received 0 broadcasts, 0 runts, 2 giants, 0 throttles
754 input errors, 752 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
144675 packets output, 25655149 bytes, 0 underruns
0 output errors, 0 collisions, 0 interface resets
0 output buffer failures, 0 output buffers swapped out
-----------------
ROUTER>sh ver
Cisco IOS Software, 7200 Software (C7200-IK9S-M), Version 12.4(5a), RELEASE SOFTWARE (fc3)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2006 by Cisco Systems, Inc.
Compiled Sat 14-Jan-06 00:25 by alnguyen
ROM: System Bootstrap, Version 12.3(4r)T3, RELEASE SOFTWARE (fc1)
BOOTLDR: 7200 Software (C7200-KBOOT-M), Version 12.3(9), RELEASE SOFTWARE (fc2)
LexKY1-8 uptime is 11 weeks, 2 days, 8 hours, 23 minutes
System returned to ROM by power-on
System restarted at 10:42:09 edt Tue Aug 8 2006
System image file is "disk2:c7200-ik9s-mz.124-5a.bin"
Cisco 7206VXR (NPE-G1) processor (revision B) with 491520K/32768K bytes of memory.
Processor board ID 34188349
SB-1 CPU at 700MHz, Implementation 1025, Rev 0.2, 512KB L2 Cache
6 slot VXR midplane, Version 2.9
Last reset from power-on
PCI bus mb1 (Slots 1, 3 and 5) has a capacity of 600 bandwidth points.
Current configuration on bus mb1 has a total of 600 bandwidth points.
This configuration is within the PCI bus capacity and is supported.
PCI bus mb2 (Slots 2, 4 and 6) has a capacity of 600 bandwidth points.
Current configuration on bus mb2 has a total of 0 bandwidth points.
This configuration is within the PCI bus capacity and is supported.
3 Gigabit Ethernet interfaces
9 ATM interfaces
1 Virtual Private Network (VPN) Module
509K bytes of NVRAM.
62592K bytes of ATA PCMCIA card at slot 2 (Sector size 512 bytes).
16384K bytes of Flash internal SIMM (Sector size 256K).
Configuration register is 0x2102
10-27-2006 12:07 PM
Since ATM divides packets into cells to transmit them across the network, all cells need to be present at the other end in order to reassemble the IP packet. If even 1 cell is dropped by the carrier network, you'll see CRC errors on your interface.
This can be caused by other sites not conforming to the CIR the provider gave them, or the provider having misconfigured policing, or even a link problem somewhere in the provider network.
Testing the T1's alone wont help here, since that is only the connection between you and the ATM edge. More times than not CRC errors are from cells being dropped within the ATM cloud.
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