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ATM Link Flapping

We have this E1 interface on a Cisco 3660 v12.2(7a)

interface ATM2/0

no ip address

ip route-cache flow

atm vc-per-vp 256

no atm ilmi-keepalive

scrambling-payload

impedance 120-ohm

!

interface ATM2/0.1 point-to-point

mtu 1500

bandwidth 512

ip address x.x.x.x x.x.x.x

pvc LUX-BHG 0/59

vbr-nrt 1130 1130 210

oam-pvc manage

oam retry 3 3 10

encapsulation aal5snap

!

and we keep getting this condition:

Mar 19 08:53:15.538: %LINEPROTO-5-UPDOWN: Line protocol on Interface ATM2/0.1, changed state to up

Mar 19 09:22:18.587: %LINEPROTO-5-UPDOWN: Line protocol on Interface ATM2/0.1, changed state to down

Mar 19 09:22:48.512: %LINEPROTO-5-UPDOWN: Line protocol on Interface ATM2/0.1, changed state to up

Mar 19 09:42:44.031: %LINEPROTO-5-UPDOWN: Line protocol on Interface ATM2/0.1, changed state to down

Mar 19 09:43:14.088: %LINEPROTO-5-UPDOWN: Line protocol on Interface ATM2/0.1, changed state to up

Mar 19 10:33:03.137: %LINEPROTO-5-UPDOWN: Line protocol on Interface ATM2/0.1, changed state to down

Mar 19 10:33:53.043: %LINEPROTO-5-UPDOWN: Line protocol on Interface ATM2/0.1, changed state to up

The link is UPDOWN all the day. We have provided the ISP with all the configuration and they say that their end is configured the same. Also, that they do not have any alarms.

What could be causing this UPDOWN problem? The impedance, the payload scrambling?

We also have increasing CRC errors - is this related?

luxcis10#sh int atm 2/0.1

ATM2/0.1 is up, line protocol is up

Hardware is ATM E1

Internet address is x.x.x.x/30

MTU 1500 bytes, BW 512 Kbit, DLY 20000 usec,

reliability 255/255, txload 42/255, rxload 74/255

Encapsulation ATM

46837703 packets input, 35780742262 bytes

28065541 packets output, 6011795941 bytes

119636 OAM cells input, 129377 OAM cells output

AAL5 CRC errors : 39371

AAL5 SAR Timeouts : 18

AAL5 Oversized SDUs : 0

AAL5 length violation : 223348

AAL5 CPI Error : 20

Any help would be greatfully appreciated!! If you need more information ,let me know and I´ll add it.

Regards, Ian.

1 ACCEPTED SOLUTION

Accepted Solutions
Silver

Re: ATM Link Flapping

the crc errors you are seeing are aal 5 errors these are caused by exceeding your contracted rate. you may want to look at tweaking your oam setting . your first value is default , your second value is lower than default this is the down parameter, default is 5 you have 3 , the third value is set to 10 this is the interval that the box will send oam f5 cells , default is 1 I would tweak the 2nd and 3rd values .

I thnk the overutilization is causing your oam cells to drop hence making line protocol bounce

1 REPLY
Silver

Re: ATM Link Flapping

the crc errors you are seeing are aal 5 errors these are caused by exceeding your contracted rate. you may want to look at tweaking your oam setting . your first value is default , your second value is lower than default this is the down parameter, default is 5 you have 3 , the third value is set to 10 this is the interval that the box will send oam f5 cells , default is 1 I would tweak the 2nd and 3rd values .

I thnk the overutilization is causing your oam cells to drop hence making line protocol bounce

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