Vigor routers support automatic load balancing which aggregate bandwidth across multiple WANs to optimize connectivity from LAN clients. However, since not all services are suitable for load balancing such as Internet banking sites, SIP calls, on-line games etc. The result is that Servers with high security levels will reject connections from different source IPs.

We will use a SIP call as an example. When a VoIP phone on the LAN sends a STUN request to the STUN server to discover the public IP via WAN1, it is possible that SIP registration to a SIP server is sent over WAN2, therefore the SIP phone will contain the IP address of WAN1 in the SIP message instead of the IP address of WAN2. This will result in the VOIP call not being established.

To prevent this connection problem, use the “Advanced” option for Load Balance Mode. This option is available in the latest firmware. It allows you to specify which traffic not be sent to the Load Balance pool.

WAN Load Balance Advanced Setting

You will also be able to configure range ports with firmware version 3.9.2 or later.