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PPP Multilink does not show traffic although related Serial link shows traffic

Kaushik Ray
Level 1
Level 1

Hello All

I would be grateful if someone could please provide some information on the following:

I am trying to troubleshoot dropped packets issues over a Serial link using ppp multilink;

one issue i am seeing which seems strange is that althought the Serial Link is showing traffic flowing through it the Multillink shows no traffic flowing. It could be that the two issues are unrelated but I am trying to find why i am seeing this strange outcome?

Has anybody seen / faced this issue before? or can advice why i could be seeing this?

thanks a lot in advance.

4 Replies 4

Jose Bogantes
Level 1
Level 1

Hello Kaushik,

Can you get the following outputs:

  • show ppp multilink
  • show run
  • show interface multilink X
  • show interface serial X/X
  • show version

Regards,

Thanks Jose for your reply; please find the details below also one thing - althought I am not see the input rate / output rate on the multilink but i see the input packets / output packets incrementing on the the multilink interface

RTR#sh ppp multilink

Multilink22

  Bundle name: Client_Sitename

  Remote Endpoint Discriminator: [1] Client_Sitename

  Local Endpoint Discriminator: [1] RTR

  Bundle up for 00:12:21, total bandwidth 512, load 240/255

  Receive buffer limit 12000 bytes, frag timeout 1000 ms

  Interleaving enabled

    0/0 fragments/bytes in reassembly list

    0 lost fragments, 0 reordered

    0/0 discarded fragments/bytes, 0 lost received

    0x14CEF received sequence, 0x12ED4 sent sequence

  Member links: 1 active, 0 inactive (max 255, min not set)

    Se1/1, since 00:12:21, 640 weight, 632 frag size

No inactive multilink interfaces

RTR#sh run int mu22

Building configuration...

Current configuration : 446 bytes

!

interface Multilink22

ip vrf forwarding Glo_VRF

ip address XXX.XXX.XXX.XXX 255.255.255.254

ip accounting output-packets

ip tcp header-compression iphc-format

load-interval 30

ppp multilink

ppp multilink interleave

ppp multilink group 22

ppp multilink fragment delay 10

no cdp enable

!

service-policy output GLOBAL_POLICY

ip rtp header-compression iphc-format

end

RTR#sh run int s1/1

Building configuration...

Current configuration : 255 bytes

!

interface Serial1/1

bandwidth 512

bandwidth inherit

no ip address

encapsulation ppp

load-interval 30

tx-ring-limit 1

ppp multilink

ppp multilink group 22

no fair-queue

!

max-reserved-bandwidth 100

end

RTR#sh int mu22

Multilink22 is up, line protocol is up

  Hardware is multilink group interface

  Internet address is XXX.XXX.XXX.XXX/31

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

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

  Encapsulation PPP, LCP Open, multilink Open

  Open: IPCP, loopback not set

  Keepalive set (10 sec)

  DTR is pulsed for 2 seconds on reset

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

  Last clearing of "show interface" counters 01:00:22

  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 25147

  Queueing strategy: Class-based queueing

  Output queue: 75/1000/0/135346 (size/max total/drops/interleaves)

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

  30 second output rate 0 bits/sec, 0 packets/sec

     452063 packets input, 62012949 bytes, 0 no buffer

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

     1 input errors, 0 CRC, 1 frame, 0 overrun, 0 ignored, 0 abort

     462943 packets output, 193210636 bytes, 0 underruns

     0 output errors, 0 collisions, 1 interface resets

     0 unknown protocol drops

     0 output buffer failures, 0 output buffers swapped out

     0 carrier transitions

RTR#sh int s 1/1

Serial1/1 is up, line protocol is up

  Hardware is M8T-X.21

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

     reliability 255/255, txload 247/255, rxload 181/255

  Encapsulation PPP, LCP Open, multilink Open

  Link is a member of Multilink bundle Multilink22, 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 01:00:32

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

  Queueing strategy: fifo

  Output queue: 1/40 (size/max)

  30 second input rate 365000 bits/sec, 244 packets/sec

  30 second output rate 496000 bits/sec, 234 packets/sec

     490280 packets input, 64912152 bytes, 0 no buffer

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

     13870 input errors, 13407 CRC, 0 frame, 44 overrun, 1 ignored, 419 abort

     585736 packets output, 193843866 bytes, 0 underruns

     0 output errors, 0 collisions, 18 interface resets

     0 unknown protocol drops

     0 output buffer failures, 0 output buffers swapped out

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

RTR#sh version

Cisco IOS Software, 7200 Software (C7200P-ADVIPSERVICESK9-M), Version 15.0(1)M4, RELEASE SOFTWARE (fc1)

Technical Support: http://www.cisco.com/techsupport

Copyright (c) 1986-2010 by Cisco Systems, Inc.

Compiled Thu 28-Oct-10 22:56 by prod_rel_team

ROM: System Bootstrap, Version 12.4(12.2r)T, RELEASE SOFTWARE (fc1)

BOOTLDR: Cisco IOS Software, 7200 Software (C7200P-BOOT-M), Version 12.4(4)XD10, RELEASE SOFTWARE (fc2)

RTR uptime is 1 year, 7 weeks, 5 days, 2 hours, 30 minutes

System returned to ROM by reload at 12:26:40 UTC Sat Mar 10 2012

System restarted at 12:28:24 UTC Sat Mar 10 2012

System image file is "disk2:c7200p-advipservicesk9-mz.150-1.M4.bin"

Last reload reason: Reload Command

This product contains cryptographic features and is subject to United

States and local country laws governing import, export, transfer and

use. Delivery of Cisco cryptographic products does not imply

third-party authority to import, export, distribute or use encryption.

Importers, exporters, distributors and users are responsible for

compliance with U.S. and local country laws. By using this product you

agree to comply with applicable laws and regulations. If you are unable

to comply with U.S. and local laws, return this product immediately.

A summary of U.S. laws governing Cisco cryptographic products may be found at:

http://www.cisco.com/wwl/export/crypto/tool/stqrg.html

If you require further assistance please contact us by sending email to

export@cisco.com.

Cisco 7206VXR (NPE-G2) processor (revision A) with 917504K/65536K bytes of memory.

Processor board ID 36405058

MPC7448 CPU at 1666Mhz, Implementation 0, Rev 2.2

6 slot VXR midplane, Version 2.11

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 0 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.

Please refer to the following document "Cisco 7200 Series Port Adaptor

Hardware Configuration Guidelines" on Cisco.com <http://www.cisco.com>

for c7200 bandwidth points oversubscription and usage guidelines.

1 FastEthernet interface

3 Gigabit Ethernet interfaces

48 Serial interfaces

2045K bytes of NVRAM.

990864K bytes of ATA PCMCIA card at slot 2 (Sector size 512 bytes).

65536K bytes of Flash internal SIMM (Sector size 512K).

Configuration register is 0x2102

Hello Kaushik,

I am not sure about a layer 1 or layer 2 issue for the "show ppp multilink" shows an active member as it is supposed to be. I guess your concern is that there are no counters related to input and output rate in the interface multilink. Is that correct?

I have some questions to isolate the issue:

  • What is the result if you send a ping towards the peer multilink?
  • Have you cleared the interface multilink? (clear interface multilink 22) Is this making a difference?

Please clear counters to make sure if the errors are still increasing or not. It is also recommended to make sure that the subnet mask is properly configured under the interface multilink.

Regards.

vmiller
Level 7
Level 7

take a look at the counters on s1/1.

    13870 input errors, 13407 CRC, 0 frame, 44 overrun, 1 ignored, 419 abort

you have a layer 1 or 2 problem with this.

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