acket loss is seen when an IRB interface is stitched to an LT interface

On all Junos MX and EX platforms, traffic loss will be seen when a L3 domain (either a VRF or default routing-instance) with an underlying IRB (Integrated Routing and Bridging) interface is stitched to another L2 domain (VPLS domain/ L2circuit/ bridge domain) with a LT (Logical Tunnel) interface acting in the access mode.

Sample Path

IP traffic source --- L3 domain --- irb.x --- lt-x/y/z.a --- lt-x/y/z.b ---> L2 domain

Configuration:

set interfaces lt-2/0/0 unit 7940 encapsulation vlan-ccc
set interfaces lt-2/0/0 unit 7940 mtu 9100
set interfaces lt-2/0/0 unit 7940 vlan-id 1310
set interfaces lt-2/0/0 unit 7940 peer-unit 7941

set interfaces irb unit 1310 enhanced-convergence
set interfaces irb unit 1310 family inet filter output 100m_filter_out
set interfaces irb unit 1310 family inet address 10.66.99.141/30

set bridge-domains bd1310 domain-type bridge
set bridge-domains bd1310 vlan-id 1310
set bridge-domains bd1310 interface lt-2/0/0.7941
set bridge-domains bd1310 routing-interface irb.1310

Packet loss on IRB to lt-x/y/z traffic flow.

 

As a workaround, enhanced-convergence can be configured on the IRB unit:

user@router# set interfaces irb unit 1310 enhanced-convergence

{master}[edit]
user@router# show | compare
[edit interfaces irb unit 1310]
+ enhanced-convergence;

{master}[edit]
user@router# commit synchronize and-quit
re0:
configuration check succeeds
re1:
commit complete
re0:
commit complete
Exiting configuration mode

The ultimate fix to avoid setting the enhanced convergence is in PR1724925:

https://prsearch.juniper.net/PR1724925