Hi all,
My scenario is as follows:
I have All the CSCFs on the same IP using different ports.
P-CSCF advertises a public IP. Rest of the nodes including I-CSCF and S-CSCF listen local only.

Behavior: When an ACK or PRACK goes from P-CSCF to S-CSCF, the RURI changes such that alias parameter is removed.
Hence, P-CSCF ends up sending PRACK and ACK on private IP of UE.

Here's what the config looks like:

listen=udp:lo.ca.l.ip:6000 advertise pu.bl.ic.ip:6000
alias=pcscf-ims.domain.net

#!define WITH_NAT

Any hints?