Description

A GRE tunnel is setup between an PTX and an MX. GRE tunnel works fine in one direction (PTX->MX) but not in the other (MX->PTX)
Traffic is not decapsulated by the PTX and is not forwarded to its destination.

Symptoms

Traffic loss in one direction.
  
user@PTX-re0> show interfaces fti0.0
  Logical interface fti0.0 (Index 13202) (SNMP ifIndex 662)
    Description: tunnel GRE
    Flags: Up Point-To-Point Encapsulation: GRE
    Source address: 10.120.110.13/32, Destination address: 10.120.110.12
    Input packets : 0
    Output packets: 42251849
    Protocol inet, MTU: 4446
      Flags: Sendbcast-pkt-to-re, User-MTU
      Addresses, Flags: Is-Preferred Is-Primary
        Local: 10.10.30.26, Broadcast: 10.10.30.27
    Protocol iso, MTU: 9171
      Flags: None
    Protocol mpls, MTU: 4446, Maximum labels: 3
      Flags: User-MTU


 

Solution

Need to enable tunnel-termination on ingress interfaces to enable GRE decapsulation. For example: 
set interfaces et-0/0/0 unit 0 family inet tunnel-termination

 
Starting from 23.1R1-EVO "tunnel-termination" can be enabled globally:
set forwarding-options tunnel-termination

Modification History

2024-08-23 : Article Created