Description

We have seen that the LDP session do not become operational when ospf3 has ipsec-sa is active.

We have both v4/v6 addresses transport-preference as ipv6.

Symptoms

set protocols ldp transport-preference ipv6
set protocols ospf3 area 0.0.0.0 interface lo0.0 passive
set protocols ospf3 area 0.0.0.0 interface ae11.10 metric 256
set protocols ospf3 area 0.0.0.0 interface ae11.10 ipsec-sa sa1
set protocols ospf3 area 0.0.0.0 interface ae12.10 metric 256
set protocols ospf3 area 0.0.0.0 interface ae12.10 ipsec-sa sa1
set protocols ospf3 export OSPFv6

show ldp session                                   
 
  Address                           State       Connection  Hold time  Adv. Mode
213.239.236.93                      Nonexistent Closed        0          DU

show ldp neighbor 

Address                             Interface       Label space ID     Hold time
213.239.236.93                      ae11.10         213.133.126.11:0     14

Solution

The driver is marking incoming packets as coming from a helper interface (iflxxxx) instead of the main one (jdtdv0).

It does this because it cannot tell whether a packet needs a security check, so it sends everything through a path where that check can happen if required.

Because of this, the helper interface must listen to the same network addresses as the main interface. Otherwise, some important packets (like certain routing messages) will not be passed up correctly.

 

This is fixed via internal PR1919313 (as of now in below releases & all later releases).

23.2R2-S7-EVO

23.4R2-S8-EVO

25.4R2-EVO

26.1R1-EVO

26.2R1-EVO

 

Workaround is to deactivate ipsec-sa in ospf3.

set protocols ospf3 area 0.0.0.0 interface lo0.0 passive
set protocols ospf3 area 0.0.0.0 interface ae11.10 metric 256
set protocols ospf3 area 0.0.0.0 interface ae11.10 ipsec-sa sa1
deactivate protocols ospf3 area 0.0.0.0 interface ae11.10 ipsec-sa
set protocols ospf3 area 0.0.0.0 interface ae12.10 metric 256
set protocols ospf3 area 0.0.0.0 interface ae12.10 ipsec-sa sa1
set protocols ospf3 export OSPFv6
 
show ldp session                                   
 
  Address                           State       Connection  Hold time  Adv. Mode
2a01:4f8:0:3::8dd                   Operational Open          27         DU

Modification History

2026-02-19 : Article Created