It would appear as though when you are using SIP ALG (Service Passthrough > SIP > Standard Mode), Outbound Policies for WAN connection preference and Outbound NAT mappings are not obeyed for SIP traffic? I am wondering if anyone else has seen this?
We have 3 WAN connections, and for all traffic originating from our SIP server to the outside world, we have the Outbound Algorithm set to priority, with the following order specified (from highest to lowest):
When SIP traffic goes out of our network, it will apparently randomly select a WAN interface. We had all SIP traffic go out over WAN 3 for a few days, then it switched to going out over WAN 1. WAN 2 is up, and other traffic is going out over it - in fact, any traffic from the SIP server OTHER than SIP traffic goes out over WAN 2, like it should. We did have SIP traffic go our over WAN 2 previously, but after a few days it switched to another WAN connection just like the behavior described above.
I also tried changing the policy to enforced, and selected WAN 2, and traffic is still going out over WAN 1.
NAT mappings also appear to be ignored for SIP traffic with SIP ALG turned on. Originally we wanted SIP traffic to go out over specific additional IP’s in our IP blocks on our 3 WAN connections, but regardless of NAT Mappings programmed in, SIP traffic would always go out via the interface IP. We figured that SIP ALG was re-writing packet headers and putting in the interface IP, so we decided to remove the NAT mappings and just allow the SIP traffic to go out via interface IP’s.
This was fine, but later on we suddenly started seeing SIP traffic leaving WAN 2 going out one of the other IP’s in that IP block, instead of the interface IP address. Even worse, this was not the IP address we originally had in the NAT mapping for that connection, which already been deleted at this point - it was another random IP in that block.
We ended up putting NAT mappings back for SIP traffic to just use the interface IP’s for each WAN connection. That worked for a while, until we noticed the above issue with Outbound WAN priority not being followed, and were advised by our support company to remove the NAT mappings, as they may be interfering with the Outbound connection priorities…
So now we are back at just having outbound traffic priority set for SIP traffic, and it not being followed. No NAT mappings.
Is anyone else using SIP ALG and seeing this same issue? Regardless of whether the Peplink is rewriting SIP headers, if I tell it to route SIP traffic out over WAN 2 and WAN 2 is up, traffic should go out over WAN 2.