Has anyone experienced and problems with the NAT on this router?
I have several of these in use, with SIP endpoints behind them. The SIP endpoints connect to an Asterisk based VoIP service that does not have a NAT proxy.
Normally when the SIP endpoint registers the VoIP server shows its private LAN side IP address (192.168.x.x). What I'm seeing is that the first endpoint to register registers with the routers public WAN side IP address. This causes problems for calls to this endpoint, and transfers.
The endpoints that register after the first registration work fine. If you force the endpoint with the routers IP to reboot and use a different LAN side IP address it registers with the LAN side IP address and works fine. If one of the other endpoints then reboots it then picks up the problem.
Its is quite noticable that the problems only ever affects one SIP endpoint behind the router. We have an install with 3 endpoints and the problem moves around one of them, and we have an install with 25 endpoints, and only 1 is affected.
Its seems to me the first endpoint on the LAN requesting SIP registration on port 5060 is being sent out on the WAN side using port 5060, and for some reason the VoIP server decides the endpoint is not behind NAT and registers the public IP address the request came in on (i.e. the routers WAN IP address).
You do see the WAN side IP address as the registered address if the router and endpoints are configured to use port forwarding (i.e. the SIP and RTP ports are forwarded).
The reason I think that forcing an LAN side IP address change on the endpoint with a problem fixes it is that the time for the endpoint to reboot, get an IP address from DHCP, and register is less that the timer the router uses to hold open the NAT mapping. The means the SIP registration does not use port 5060 on the WAN side.
The problems reoccurs on other endpoints as once NAT mapping expires for the first session the next request for a new connection on port 5060 will go out on the WAN side on port 5060.
I would greatly appreciate any comments from other users of Cisco/Linksys routers that have had similar problems.
Rob.
I have several of these in use, with SIP endpoints behind them. The SIP endpoints connect to an Asterisk based VoIP service that does not have a NAT proxy.
Normally when the SIP endpoint registers the VoIP server shows its private LAN side IP address (192.168.x.x). What I'm seeing is that the first endpoint to register registers with the routers public WAN side IP address. This causes problems for calls to this endpoint, and transfers.
The endpoints that register after the first registration work fine. If you force the endpoint with the routers IP to reboot and use a different LAN side IP address it registers with the LAN side IP address and works fine. If one of the other endpoints then reboots it then picks up the problem.
Its is quite noticable that the problems only ever affects one SIP endpoint behind the router. We have an install with 3 endpoints and the problem moves around one of them, and we have an install with 25 endpoints, and only 1 is affected.
Its seems to me the first endpoint on the LAN requesting SIP registration on port 5060 is being sent out on the WAN side using port 5060, and for some reason the VoIP server decides the endpoint is not behind NAT and registers the public IP address the request came in on (i.e. the routers WAN IP address).
You do see the WAN side IP address as the registered address if the router and endpoints are configured to use port forwarding (i.e. the SIP and RTP ports are forwarded).
The reason I think that forcing an LAN side IP address change on the endpoint with a problem fixes it is that the time for the endpoint to reboot, get an IP address from DHCP, and register is less that the timer the router uses to hold open the NAT mapping. The means the SIP registration does not use port 5060 on the WAN side.
The problems reoccurs on other endpoints as once NAT mapping expires for the first session the next request for a new connection on port 5060 will go out on the WAN side on port 5060.
I would greatly appreciate any comments from other users of Cisco/Linksys routers that have had similar problems.
Rob.
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