If an ISP allocates a block public IP addresses to you, then you can set these up as an IP Routed Subnet or a Routing Usage LAN.

1. Go to WAN >> General Setup, configure a WAN profile according to what the ISP has provided.

2. Go to LAN >> General Setup, select the LAN profile you want to use for the public IP addresses. In the More Subnet field, click Add to add a subnet as follows:

a. IP: The router’s LAN IP (this can be the same IP as the Vigor3900’s WAN IP)
b. Subnet Mask: the subnet you want to use on the LAN. This should be equal to or smaller than the Subnet Mask configured on the WAN.
c. Mode: ROUTING
d. Save and then Apply the LAN profile.

3. Go to Routing >> Static Route >> LAN/WAN Proxy ARP. Bind the LAN profile and the WAN profile.

LAN/WAN Proxy ARP makes the Vigor3900 respond to the ARP request for the selected LAN network from the WAN side. For instance, if the Routing LAN PC uses IP 211.211.211.154 in the Vigor3900’s LAN network, and the Vigor3900 receives an ARP request from that IP on its WAN interface, with LAN/WAN Proxy ARP enabled, the Vigor3900 will respond to the ARP request on the WAN Gateway. If there is only a LAN client using the public IP in the Routing LAN, we can configure the LAN client’s IP only (with the subnet mask 32).

4. For the LAN host using the public IP, configure a static IP address at TCP/IP configuration, where the IP address should be different from that of the router, the subnet mask should be the same, and gateway should be the router’s LAN IP address.

5. Finally, go to Routing >> Policy Route. Create a rule to allow the Routing LAN network go via the corresponding WAN profile.

Additionally, if there is a second WAN which has a public IP addresses for the LAN host, you can add another subnet in the LAN profile.

Specify the second IP range to the second WAN at Routing >> Static Route >> LAN/WAN Proxy ARP.

And then create a policy route rule to allow the second Routing LAN go out through the corresponding WAN interface.

Trouble-shooting

If a PC with a public IP address cannot access the Internet after above configuration, please check:

  • If the public IP address has been used by another device.
  • If the router’s WAN Access Mode is “Static or Dynamic IP”. Make sure the subnet mask of the WAN interface is larger than that of LAN interface.

If none of the above helps, try changing the host’s Gateway from the router’s IP (211.211.211.153) to the WAN Gateway IP (211.211.211.158), and connect the host to the ISP Modem directly and try again.