This article explains how to enable OAM protocol over the GRE tunnel with proper configuration.

In case, BGP is running over GRE with an IPv6 address, then the BGP neighbour might go DOWN after enabling the OAM protocol.

Generic routing encapsulation (GRE) tunnel interfaces do not have a built-in mechanism for detecting when a tunnel is down. Keepalive messages help the GRE tunnel interfaces detect when a tunnel is down.

Use the below configuration to correctly enable the OAM protocol over the GRE tunnel:

Keep-alive timers:

set protocols oam gre-tunnel interface gr-0/0/0.0 keepalive-time 3
set protocols oam gre-tunnel interface gr-0/0/0.0 hold-time 6

Note that the hold time must be at least twice the keepalive time.

GRE Configuration:

gr-0/0/0{
        unit 0 {
            tunnel {
                source 10.10.10.1;
                destination 10.10.10.2;
            }
            family inet6 {
                address 2001:xxxx:xxxx::/64;
            }
            family inet {                     << family inet is mandatory for enabling keep-alive
        }
    }
}

Mandatory statement:

set interfaces gr-0/0/0 unit <> family inet

Note: For proper operation of keepalives on a GRE interface, you must also include the family inet statement at the [edit interfaces interface-name unit unit] hierarchy level. If you do not include this statement, the interface is marked as down.

In case the issue is not resolved by the above steps,  please contact JTAC for further investigation.