TIPS Multi-homed confusion

[Donb123]

Existing IncrediblePBX install runs great. I have a SIP trunk which is 1 hop away on a private subnet (Digium PRI gateway). I am adding a SIP trunk from an external provider and the link to that is a direct Internet IP that I've added as a second NIC. So I have a couple of private subnets setup with localnets and the external net is currently the old IP and NAT=never.

I've tried to make this work with an IP route to the -host of the new SIP trunk and leaving the default gateway as the private IP VLAN and that doesn't work. I've tried changing the external IP in SIP settings and that doesn't work.

If I disable the existing eth device then the external trunk works but I'm not able to get both at the same time. I would have thought that IP routing would handle this but I was apparently wrong. Any advice would be greatly appreciated!

 

[Samot]

This is a routing issue. You need to look at the routing on the system. If the two interfaces are eth0 (private) and eth1 (public) then you most likely have a default route that goes over eth0.

I would make the public facing trunk a Chan_PJSIP trunk so you can setup a public transport that binds to the public IP assigned to the PBX. That way requests source from that IP off the PBX and the routes for that IP and subnet should route normally. If they are still going out eth0 then you'll need to make a route for this that forces requests from that public IP to go out its gateway.

 

[Donb123]

I do in fact have a default route for the internal eth0. I did a route add -host x.x.x.x gw y.y.y.y.y (external device) and that pings and traceroutes.

I was using Chan_SIP. I'll try PJSIP.

 

[Samot]

I do in fact have a default route for the internal eth0. I did a route add -host x.x.x.x gw y.y.y.y.y (external device) and that pings and traceroutes.

I was using Chan_SIP. I'll try PJSIP.

Yeah the problem with Chan_SIP is it can bind to 0.0.0.0 (all interfaces) or x.x.x.x (specific interface) so it if it's 0.0.0.0 there's no guarantee it's actually sourcing from the host you have that route set for.

 

[Donb123]

Wait.. that means I have to get the SIP provider to change over to port 5061 or change all my internal devices to use 5061 since they're Chan_SIP already on 5060?

 

[Samot]

Wait.. that means I have to get the SIP provider to change over to port 5061 or change all my internal devices to use 5061 since they're Chan_SIP already on 5060?

Only the trunk needs to use 5061. So if you are registering to them, this won't be a problem. If you're using IP Auth and routing incoming requests from them based on IP/Port you need to update that.

 

[billsimon]

My tip would be to do your routing with a router and not with multiple NICs on a server.

 

[Donb123]

My tip would be to do your routing with a router and not with multiple NICs on a server.

I literally have a stand-alone fiber optic cable that uses public IP that is provided for the exclusive task of SIP. The existing network has a router and works quite fine.

 

[billsimon]

I literally have a stand-alone fiber optic cable that uses public IP that is provided for the exclusive task of SIP. The existing network has a router and works quite fine.

Yeah, I'm saying literally plug that into a router interface. It's what routers are meant for. The point is that you won't have to do anything special with the PBX; it will make the configuration easier.

 

[Donb123]

Yeah, I'm saying literally plug that into a router interface. It's what routers are meant for. The point is that you won't have to do anything special with the PBX; it will make the configuration easier.

Honestly, I've been thinking about doing that. I'm not making much progress it seems.