SIP Trunk failover and routing with multiple ISPs

[hallocje]

We have an IP Office 500 v2 and we have it configured as 1:1 NAT via our Cisco ASA firewall for the IPO. Our SIP trunk provider configures access via IP and does not do any other authentication. It works fine in that scenario. However, we have had a lot of issues with internet service and we now have a backup ISP for which internet access fails over in the event that the primary link goes down. When this happens, the inbound/outbound phone service stops working. The SIP trunk provider only does IP authentication, so we have to have an external IP for both ISPs configured for the IPO to work when internet fails over. We have a single internal IP, and we have 2 external IPs. I have looked through documentation and forum posts but just can't find anything with this scenario. Is there a way to configure two external IPs in the IPO and have it route properly depending on which ISP is providing internet service?

 

[TouchToneTommy]

A 2nd IPO configured with an SCN to your existing IPO can have the alternate ISP's public IP entered in the Network Topology and still have a default route through the alternate ISP

If SIP ALG's actually worked properly, your firewall could handle sending the proper public IP to the SIP carrier

We have a SDWAN provider, they publish a public IP that belongs to them, and routes to the site via whichever internet connection is up and running, so the ISP connection to the site can change, but the public IP will remain static

 

[mforrence]

We use Adtran 3140 router with SBC for this application - works like a champ.

Mike Forrence

http://www.goteamvox.com