Agent registration cache - how to avoid the look up

Hi all,

I have a scenario as below. Agent registration is working OK and the registration cache contains the 13byte cookie when sbc send out the registration to the third party sbc.

[soft phone behind NAT]----->[(Access) SBC (Core)] ------> [third party SBC ]------>[SIP server registrar ]

   SD Info:

    Contact: sip:50000-4k0jrqaqfnabd@10.X.X.X:5060

    Realm: realm-test

When there are incoming calls to the agent, the Invite RURI comes only with agent extension number without the cookie. Hence the registration cache look up fails. It seems third party sbc is not passing the contact header to SIP server.