Description

The l2circuit tunnels between an ACX1100 and ACX5048, stop working when the new ACX7024 is inserted


Symptoms

root@JTAC> show l2circuit connections

Layer-2 Circuit Connections:

 

Legend for connection status (St)

EI -- encapsulation invalid NP -- interface h/w not present

MM -- mtu mismatch Dn -- down

EM -- encapsulation mismatch VC-Dn -- Virtual circuit Down

CM -- control-word mismatch Up -- operational

VM -- vlan id mismatch CF -- Call admission control failure

OL -- no outgoing label IB -- TDM incompatible bitrate

NC -- intf encaps not CCC/TCC TM -- TDM misconfiguration

BK -- Backup Connection ST -- Standby Connection

CB -- rcvd cell-bundle size bad SP -- Static Pseudowire

LD -- local site signaled down RS -- remote site standby

RD -- remote site signaled down HS -- Hot-standby Connection

XX -- unknown

 

Legend for interface status

Up -- operational

Dn -- down

Neighbor: a.b.c.d

Interface Type St Time last up # Up trans

ae20.2100(vc 130) rmt VC-Dn ----- 0

Remote PE: 192.168.1.130, Negotiated control-word: No

Incoming label: 451328, Outgoing label: 1931

Negotiated PW status TLV: No

Local interface: ae20.2100, Status: Up, Encapsulation: ETHERNET

Flow Label Transmit: No, Flow Label Receive: No

ge-0/0/3.0(vc 500) rmt XX

Neighbor: 192.168.1.131

Interface Type St Time last up # Up trans

ge-0/0/2.770(vc 770) rmt LD

Neighbor: 192.168.1.141

Interface Type St Time last up # Up trans

ge-0/0/2.770(vc 770) rmt LD

Neighbor: 192.168.1.175

Interface Type St Time last up # Up trans

ae20.2100(vc 130) rmt BK

ge-0/0/3.0(vc 500) rmt BK

Neighbor: 192.168.1.234

Interface Type St Time last up # Up trans

ae23.0(vc 111) rmt VC-Dn ----- 0

Remote PE: 192.168.1.234, Negotiated control-word: Yes (Null)

Incoming label: 299792, Outgoing label: 320256

Negotiated PW status TLV: No

Local interface: ae23.0, Status: Up, Encapsulation: ETHERNET

Flow Label Transmit: No, Flow Label Receive: No

Solution

Topology:

ACX5048 <-> ACX7024 <-> ACX1100

 

Observations:

> We observed that LDP session was flapping when interface was up.

> The session from ACX7024 & ACX5048, towards the ACX1100 was flapping.

> We could also see the interface going down between ACX7024 & ACX1100.

> Customer also confirmed that there are no issues for the l2ckt terminated on ACX7024.

> Further checking logs, we can see the reason for LDP session down at ACX7024 is "received notification from peer".

> Upon checking the ACX1100, we can see "hold time expired" for the LDP down events.

> There are no errors or drops seen for interfaces (ae & physical) on both side.

> But the config has some concerns, as while we have link speed being configured as 1g on ACX7024, the other end is having 100m speed config on interface.

> This is contradictory & could be the reason for the LDP flaps (interface speed is displayed 'Unspecified' in ACX7024 ae2).

 

ACX7024 Config:

  ae2 {

    traps;

    mtu 4470;

    aggregated-ether-options {

      minimum-links 1;

      link-speed 1g; <<<<<

|

Physical interface: ae2, Enabled, Physical link is Down

 Interface index: 1006, SNMP ifIndex: 597, Generation: 609885357016

 Link-level type: Ethernet, MTU: 4470, Speed: Unspecified, <<<<<

 

ACX1100 Config:

  ge-0/0/1 {

    speed 100m; <<<<<

    gigether-options {

      802.3ad ae2;

    }

  }

  ae2 {

    traps;

    mtu 4470;

    aggregated-ether-options {

      minimum-links 1;

      lacp {

|

Physical interface: ae2, Enabled, Physical link is Up

 Interface index: 128, SNMP ifIndex: 516, Generation: 131

 Link-level type: Ethernet, MTU: 4470, Speed: 100mbps, <<<<<

 

Solution:

Removed 100m config from ACX1100 child interface (ge-0/0/1), towards ACX7024.

And also set "speed 1g" in physical interface of ACX7024, which resolved the issue.

Modification History

2025-03-28 : Article Created