HT812 - LAN DHCP BASE IP - auto adjust working?



When connecting an HT812 with the firmware to a router or modem assigning client devices IPs in the range to with the host as, the Base IP address for the LAN port has a default of which conflicts with the WAN IP host and is supposed to change based on the network mask ( so the subnet should be increased by 1 to

I cannot seem to get this to work which results in the ATA not working when connected to a modem/router with a host base IP of Changing the ATA DHCP Base IP or the host IP to something other than works but as I understand it, this function in the ATA should automatically detect and change it.



Can you advise where you saw or understood that the HT would automatically change its IP based upon a subnet mask?

I don’t know of any such device that will do that.
You can set the HT to DHCP and then either allow it to pick up a randomly assigned IP from the router’s DHCP server or, better yet, make a reservation in the router for a specified IP of your choice.
You can set the HT with a static IP of your choice.

Presumably, the subnet mask of /24 only allows the IPs within that segment as you have already stated. The HT knows nothing about the IP of the router and having it jump by a segment using that subnet mask would make it unreachable by the very network you connected it to.


When the ATA gets it’s WAN IP from the host device it would/should know if there is a conflict with the assigned gateway/WAN subnet compared to the LAN DHCP base IP

From the Admin guide for the HT8xx:
[LAN DHCP Base IP] - Base IP Address for a LAN port. Default factory setting is Note: When the device detects WAN IP is conflicting with LAN IP, the LAN base IP address will be changed based on the network mask – the effective subnet will be increased by 1. For example; will be changed to if net mask is Then the device will reboot

Based on this it would seem that if I connect a HT812 to a device such as a Sagemcom 5250 modem, both have DHCP addresses of so the HT812 should say Hey! I’m changing to


I think it means that if the wan IP of the ht is made to be the same as the lan IP of the ht…the ht lan IP will increment automatically. So, my reading is that if the wan of the ht is assigned the same IP as the ht lan, the lan IP of the ht will increment, not the wan. The ht has no idea of the router.

That’s how I read, but to be honest I never knew that. I will have to try and see.


Have still been working on this but no progress. The main reason for wanting this is to eliminate one of the points of failure users have, namely when the modem and ATA both have the base IP of Just trying to make the ATA more plug and play for users… Any help would be greatly appreciate as this seems to be a feature of the HT81x that is not working.


I had the same problem. My ASUS router uses as its default IP address. The Grandstream HT812 did not automatically renumber the LAN assignment as user Wintermute suggested. It took an hour of troubleshooting to figure out what the problem is - since I couldn’t get access to the web interface and the LAN IP address isn’t accessible through the telephone prompts, it wasn’t immediately apparent. At first I thought it was the subnet mask (the default is strangely set to, I can’t imagine anyone on a home LAN has a /16 space). Then I thought maybe the new RJ45 patch cable was defective. Last, I thought to try plugging directly into the LAN port and pulling a dynamic IP address (which clued me into the assigned subnet from what my computer pulled, leading me to guess what the LAN IP of the HT812 might be).

Glad I have 15 years of *nix admin / network admin experience. If I was a consumer, I probably would have returned the device as unusable. The web interface and documentation could really use some attention. Too many options - no hover-over help tooltips - manual just copy and pastes most options without explaining what they are. The “Basic” and “Advanced” tabs are not really indicative of what they are, either. Many options on “Basic” are fairly advanced.