AAL5 CRC error 7200

ahurtadove · ‎11-08-2011

Hello, I know this has been discussed a gazillion times, but I haven't seen relation in any of the threads that I read to this case.

One of our clients is having the situation where is receiving AAL5 CRC errors in it's ATM interface. I've read some posts and some Cisco documentation and it does not seem to be HW problem because it's happening on almost every device terminating the VC's, also it's not a cosmetic problem because the client is indeed having VC's flapping connections so it looses connectivity every now and then. I cannot have all configurations due to access restrictions but I will post some configs present in one of the devices. PLEASE do help me.

ATM4/0 is up, line protocol is up

Hardware is ENHANCED ATM PA

Description: ATM P6-10-1

MTU 4470 bytes, sub MTU 4470, BW 149760 Kbit, DLY 80 usec,

reliability 213/255, txload 1/255, rxload 1/255

Encapsulation ATM, loopback not set

Encapsulation(s): AAL5

4095 maximum active VCs, 11 current VCCs

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 3d18h

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

Queueing strategy: Per VC Queueing

30 second input rate 0 bits/sec, 1 packets/sec

30 second output rate 9000 bits/sec, 4 packets/sec

544367 packets input, 83978083 bytes, 0 no buffer

Received 0 broadcasts, 0 runts, 280 giants, 0 throttles

285201 input errors, 400799 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort

5482924 packets output, 1836276034 bytes, 0 underruns

0 output errors, 0 collisions, 0 interface resets

0 output buffer failures, 0 output buffers swapped out

ATM4/0.101 is up, line protocol is up

Hardware is ENHANCED ATM PA

Internet address is XXXXXXXXX

MTU 4470 bytes, BW 1 Kbit, DLY 80 usec,

reliability 213/255, txload 1/255, rxload 1/255

Encapsulation ATM

85134 packets input, 10930656 bytes

78124 packets output, 6601753 bytes

0 OAM cells input, 0 OAM cells output

AAL5 CRC errors : 10

AAL5 SAR Timeouts : 0

AAL5 Oversized SDUs : 0

ATM4/0.102 is up, line protocol is up

Hardware is ENHANCED ATM PA

Internet address is XXXXXXXXXXXXX

MTU 4470 bytes, BW 992 Kbit, DLY 80 usec,

reliability 213/255, txload 1/255, rxload 1/255

Encapsulation ATM

249384 packets input, 51482388 bytes

749907 packets output, 169020090 bytes

0 OAM cells input, 0 OAM cells output

AAL5 CRC errors : 13

AAL5 SAR Timeouts : 0

AAL5 Oversized SDUs : 0

ATM4/0.103 is up, line protocol is up

Hardware is ENHANCED ATM PA

Internet address is XXXXXXX

MTU 4470 bytes, BW 992 Kbit, DLY 80 usec,

reliability 213/255, txload 1/255, rxload 1/255

Encapsulation ATM

22463 packets input, 4302727 bytes

120829 packets output, 36382615 bytes

0 OAM cells input, 0 OAM cells output

AAL5 CRC errors : 64940

AAL5 SAR Timeouts : 0

AAL5 Oversized SDUs : 0

Here's the configuration for each interface:

interface ATM4/0

description ATM P6-10-1

no ip address

ip route-cache flow

load-interval 30

atm sonet stm-1

no atm auto-configuration

atm ilmi-keepalive 10

!

interface ATM4/0.101 point-to-point

bandwidth 1

ip address XXXXXXXXXX

pvc XXX 3/101

ubr 2234

no ilmi manage

oam-pvc 0

encapsulation aal5snap

!

interface ATM4/0.102 point-to-point

bandwidth 992

ip address XXXXXXXXXXXXXX

pvc XXX 3/102

ubr 2234

no ilmi manage

oam-pvc 0

encapsulation aal5snap

!

interface ATM4/0.103 point-to-point

bandwidth 992

ip address XXXXXXXXXXXX

pvc XXX 4/103

ubr 2234

no ilmi manage

oam-pvc 0

encapsulation aal5snap

Thank you very much for your help

vmiller · ‎11-09-2011

when you state "does not seem to be HW problem because it's happening on almost every device terminating the vcs" are there other routers terminating ATM that show the same issue?

If its just this one, I'd swap the cable on interface ATM4/0 for starters.

What is ATM4/0 physically connected to/

Giuseppe Larosa · ‎11-09-2011

Hello Antonio,

in addition to checking the cables as suggested by vmiller have a look at

http://www.cisco.com/en/US/tech/tk39/tk48/technologies_tech_note09186a0080094ba1.shtml

http://www.cisco.com/en/US/tech/tk39/tk48/technologies_tech_note09186a00800c93ef.shtml

two notes:

one VC looks like much more affected then others and this would point to the remote side of that VC.

An AAL5 PDU can be made of several ATM cells so be prepared to see some numbers not aligned this is ATM specific.

I guess this ATM Sonet or SDH is used for backup purposes as the traffic load is low.

if only some VCs show errors you should investigate them, and it may be wise to open a ticket with WAN provider and to perform loopback tests on the remote end to see what happens. You also have ATM OAM disabled that does not allow to monitor the VC status.

It requires time and patience to fix it but it should be possible with the methodology described above, loopback tests are intrusive so they can be performed easily only if remote sites have other links to connect to the HQ otherwise you need a maintanance window.

Hope to help

Giuseppe

ahurtadove · ‎11-09-2011

Hello, the cable has already been checked, this device is from a Service Provider and they opened a ticket to us. There are like 7 more VC's in this but I only posted some because of space but all the rest of the VC's have the same high number of CRC's.

I may recommend the client to configure ATM OAM, so I will be looking to some documentation and see how it's done.

This client is very reserved with everything so I'm working wuth my nails here, I will visit the site and retrieve more info, and I'll keep you updated.

Thanks for your help