Description


On Junos PTX and QFX10K platforms with node protection enabled on a Multicast Virtual Private Network (MVPN) scenario, multicast traffic loss will be seen when the number of child links in an aggregated ethernet (AE) interface for bypass Label Switched Path (LSP) egress interface is higher than primary LSP and one of the child links goes down on primary LSP egress interface.



User@Router> show mpls lsp name 172.16.2.7:100:5:mvpn:PRIMARY-MVPN extensive | no-more
 
Transit LSP: 1669 sessions
 
172.16.2.7
From: 172.16.2.3, LSPstate: Up, ActiveRoute: 0
LSPname: 172.16.2.7:100:5:mvpn:PRIMARY-MVPN, LSPpath: Primary
P2MP LSPname: 100:5:mvpn:PRIMARY-MVPN, Re-merge: Head
Suggested label received: -, Suggested label sent: -
Recovery label received: -, Recovery label sent: 662025
Resv style: 1 SE, Label in: 232234, Label out: 662025
Time left: 5301, Since: Thu May 1 20:36:38 2025
Tspec: rate 15Gbps size 15Gbps peak Infbps m 20 M 1500
Port number: sender 95 receiver 33192 protocol 0
P2MP branch id: 1884, Subgroup Originator: 172.16.2.3
Link protection desired
Type: Link protected LSP, using Bypass->172.16.1.94
1 May 1 20:36:39 Link protection up, using Bypass->172.16.1.94
Enhanced FRR: Enabled (Upstream), LP-MP for 172.17.249.66
Enhanced FRR: Enabled (Downstream), LP-MP is 172.16.2.205
PATH rcvfrom: 172.16.0.222 (ae7.0) 3 pkts
incoming message handle: P-63350678/3, Message ID: 233223143, Epoch: 16184696
Adspec: received MTU 1500 sent MTU 1500
PATH sentto: 172.16.1.94 (ae9.0) 3 pkts
outgoing message state: refreshing, Message ID: 214701875, Epoch: 16182353
RESV rcvfrom: 172.16.1.94 (ae9.0) 4 pkts, Entropy label: Yes
incoming message handle: R-63350683/4, Message ID: 98688384, Epoch: 15584337
RESV
 
 
 
User@Router> show mpls lsp bypass name Bypass->172.16.1.94 extensive | no-more
Ingress LSP: 5 sessions
 
172.16.2.205
From: 172.17.249.67, LSPstate: Up, ActiveRoute: 0
LSPname: Bypass->172.16.1.94
LSPtype: Static Configured
Suggested label received: -, Suggested label sent: -
Recovery label received: -, Recovery label sent: 301286
Resv style: 1 SE, Label in: -, Label out: 301286
Time left: -, Since: Thu May 1 16:45:14 2025
Tspec: rate 0bps size 0bps peak Infbps m 20 M 1500
Port number: sender 1 receiver 34484 protocol 0
Type: Bypass LSP
Number of data route tunnel through: 276
Number of RSVP session tunnel through: 0
Number of protected LSP instances: 276
Enhanced FRR: Enabled (Downstream)
PATH rcvfrom: localclient
Adspec: sent MTU 1500
Path MTU: received 1500
PATH sentto: 172.16.0.222 (ae7.0) 1 pkts
outgoing message state: refreshing, Message ID: 214656680, Epoch: 16182353
RESV rcvfrom: 172.16.0.222 (ae7.0) 1 pkts, Entropy label: Yes
incoming message handle: R-63336954/1, Message ID: 233169584, Epoch: 16184696
Explct route: 172.16.0.222 172.16.4.131 172.16.1.178 172.16.1.195 172.16.0.141 172.16.0.143 172.16.1.16 172.16.1.30 172.16.0.28 172.16.1.28 172.16.1.91 172.16.1.106 172.16.0.50
Record route: <self> 172.16.0.222 172.16.4.131 172.16.1.178 172.16.1.195 172.16.0.141 172.16.0.143 172.16.1.16 172.16.1.30 172.16.0.28 172.16.1.28 172.16.1.91 172.16.1.106 172.16.0.50
 
 
{master}
User@Router> show interfaces terse | match ae7
et-0/0/0.0 up up aenet --> ae7.0
et-0/0/1.0 up up aenet --> ae7.0
et-0/0/2.0 up up aenet --> ae7.0
et-0/0/3.0 up up aenet --> ae7.0
et-0/0/4.0 up up aenet --> ae7.0
et-0/0/5.0 up up aenet --> ae7.0
et-0/0/6.0 up up aenet --> ae7.0
et-0/0/7.0 up up aenet --> ae7.0
et-0/0/8.0 up up aenet --> ae7.0
et-0/0/9.0 up up aenet --> ae7.0
et-0/0/10.0 up up aenet --> ae7.0
et-0/0/11.0 up up aenet --> ae7.0
et-0/0/12.0 up up aenet --> ae7.0
et-0/0/13.0 up up aenet --> ae7.0
et-0/0/14.0 up up aenet --> ae7.0
ae7 up up
ae7.0 up up inet 172.16.0.223/31
 
{master}
User@Router>
 
 
{master}
User@Router> show interfaces terse | match ae9
et-3/0/4.0 up up aenet --> ae9.0
et-3/0/5.0 up up aenet --> ae9.0
et-3/0/6.0 up up aenet --> ae9.0
et-3/0/7.0 up up aenet --> ae9.0
ae9 up up
ae9.0 up up inet 172.16.1.95/31
 
Here number of links in primary path is less than the bypass.

Primary path : ae9
Bypass : ae7

Symptoms

 

After a child link in an AE interface used as egress interface for primary LSP goes down, if bypass LSP is using an AE interface with more child links than primary LSP, multicast traffic loss will be seen due to an error while programming multicast replication tree. This issue is only seen on MVPN with node protection scenario.

 

 vty command "show pechip trapstats" will have below trapcode incrementing when we see this issue.

DEV        TRAPCODE                                           count                 rate
=========================================================================================
...
0 ( 250) sw.egnh.cfg_discard                            79677850                67033


Solution


Pre-Occurrence: 
    Make sure that child link of Primary LSP's egress interface with highest child link is all in UP state.

Post-Occurrence: 
    Workaround is to remove the child link which has gone down from the Primary LSP egress interface or make sure child link state is UP.

Modification History

2025-09-08 : Article Created