Multilink PPP Problem

[thomas.ellwanger]

Hello,

I configured a Multilink Interface with two Serial Interfaces Ser1a-Ser1b and Ser2a-Ser2b. This Configuration works between 1 and 2 Days then no IP Packet goes over the Multilink Interface, in this State all Interfaces Multilink1a, Multilink1b, Ser1a, Ser1b, Ser2a an Ser2b are up. I reset one of the Serial Interfaces, then the Multilink is ok.

The Configuration is:

interface Multilink1

ip address xxx.yyy.zzz.xxx xxx.xxx.xxx.xxx

no cdp enable

ppp multilink

multilink-group 1

interface Serial2/0

bandwidth 1920

no ip address

encapsulation ppp

no ip mroute-cache

no keepalive

no peer default ip address

no fair-queue

no cdp enable

ppp multilink

multilink-group 1

hold-queue 4096 in

hold-queue 4096 out

!

interface Serial2/1

bandwidth 1920

no ip address

encapsulation ppp

no ip mroute-cache

no keepalive

no peer default ip address

no fair-queue

no cdp enable

ppp quality 80

ppp multilink

multilink-group 1

hold-queue 4096 in

hold-queue 4096 out

What am i doing wrong?

Any Help is welcome

Regards

Thomas

[deilert]

on S2/1 you are using ppp quality 80 this could be the reason it stops functioning , when you reset the interface the reliability is reset .

Are there any erros on s2/1 or what it is attached to ?

[thomas.ellwanger]

Hello,

thank you for your fast response. I made a mistake with copy and paste "ppp quality is configured on all serial interfaces and in the moment we are using the multilink with only one serial connection without any problems. Only with two serials the problem occurs.

I have no errors on the serial interfaces.

Attached on the serial interfaces are Controlware Primus G.703 -> X21 Converter.

Regards

Thomas

[deilert]

what do the serial interfaces on the remote side look like ?

[thomas.ellwanger]

Hello,

the configuration of the Interfaces is identical.

Regards

Thomas

[deilert]

can you paste in a sh interface serial x from both ends

[deilert]

can you paste in a sh interface serial x from both ends

[thomas.ellwanger]

Hello,

for the Moment only one serial connection is in the Multilink.

Router a ser 2/1 is connected with Router b ser 2/0

Router a

#sh int ser 2/1

Serial2/1 is up, line protocol is up

Hardware is M4T

Description: xxxxxxxxxxxxxxxxxxxxxxxx

MTU 1500 bytes, BW 1920 Kbit, DLY 20000 usec,

reliability 255/255, txload 17/255, rxload 76/255

Encapsulation PPP, crc 16, loopback not set

Keepalive not set

LCP Open, multilink Open

Last input 00:00:00, output 00:00:00, output hang never

Last clearing of "show interface" counters 1w0d

Queueing strategy: fifo

Output queue 0/4096, 0 drops; input queue 24/4096, 0 drops

5 minute input rate 573000 bits/sec, 79 packets/sec

5 minute output rate 133000 bits/sec, 62 packets/sec

29950357 packets input, 335251973 bytes, 0 no buffer

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

136 input errors, 112 CRC, 0 frame, 0 overrun, 0 ignored, 24 abort

26648262 packets output, 354103059 bytes, 0 underruns

0 output errors, 0 collisions, 0 interface resets

0 output buffer failures, 0 output buffers swapped out

0 carrier transitions DCD=up DSR=up DTR=up RTS=up CTS=up

Router b

#sh int ser 2/0

Serial2/0 is up, line protocol is up

Hardware is M4T

Description:xxxxxxxxxxxxxxxxxxxxxxxxxxx

MTU 1500 bytes, BW 1920 Kbit, DLY 20000 usec,

reliability 255/255, txload 108/255, rxload 38/255

Encapsulation PPP, crc 16, loopback not set

Keepalive not set

LCP Open, multilink Open

Last input 00:00:00, output 00:00:00, output hang never

Last clearing of "show interface" counters 3w0d

Queueing strategy: fifo

Output queue 0/4096, 0 drops; input queue 462/4096, 0 drops

5 minute input rate 292000 bits/sec, 101 packets/sec

5 minute output rate 816000 bits/sec, 124 packets/sec

70469717 packets input, 615352921 bytes, 144 no buffer

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

55 input errors, 38 CRC, 0 frame, 0 overrun, 0 ignored, 17 abort

78739185 packets output, 2191565971 bytes, 0 underruns

0 output errors, 0 collisions, 38 interface resets

0 output buffer failures, 0 output buffers swapped out

38 carrier transitions DCD=up DSR=up DTR=up RTS=up CTS=up

Regards

Thomas

[deilert]

you are taking errors and carrier transitions across this link , I would clear the counters and watch it , when it happens again look to see if you received a burst of errors or carrier transtions that could have caused this , If you have an internal CSU you can do a sh service-module serialx performance stats , this will give you the last 96 15 minute intervals and how many errors occured during these times .

[fbadr]

Hi

it's a IOS bug ,try to upgrade the ios or try

to put fair-queue on all interface

[thomas.ellwanger]

Hello,

we are using IOS Version 12.2(1)on Cisco 3640. Do you know the release in which the bug was fixed.

Regards

Thomas

[thomas.ellwanger]

Hello,

thank you for your response.

Can you tell me why enabling fair-queue can solve the problem.

Regards

Thomas