hi,

i have kamailio+rtpengine acting as a SBC (private/public net interfaces)

kamailio 5.4.x/rtpengine 9.x/centos 7

using TOPOH module

modparam("topoh", "mask_ip", "public_IP")

i'm rewriting IPs in INVITE like this

 $var(ruri) = "sip:" + $(ru{re.subst,/private_IP/public_IP/g});
                $ru = $(ru{re.subst,/private_IP/public_IP/g});
                $tu = $(tu{re.subst,/private_IP/public_IP/g});
                $fu = $(fu{re.subst,/remote_private_IP/public_IP/g});
the same for route[WITHINDIALOG] and INVITE

i have problem with session timers using re-INVITE method

in the first INVITE SDP is correct

c=IN IP4 public_IP

but

in the reinvite is

c=IN IP4 private_IP

and remote SBC drop with 422 because SDP is changed and SDP version is not.

any tips / best practice?

thanks

Marek