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iPBX30 User Manual
6.2.3 Configuring DNS Relay
When you specify the device's LAN port IP address as the DNS
address, then the Internet Security Router automatically performs
"DNS relay"; i.e., because the device itself is not a DNS server, it
forwards domain name lookup requests from the LAN PCs to a
DNS server at the ISP. It then relays the DNS server's response to
the PC.
When performing DNS relay, the iPBX30 must maintain the IP
addresses of the DNS servers it contacts. It can learn these
addresses in either or both of the following ways:
• Learned through PPPoE or Dynamic IP Connection: If the
iPBX30 uses a PPPoE (see section 5.2.2 PPPoE or 5.2.3
PPPoE or Dynamic IP (see section 5.2.4 Dynamic IP)
connection to the ISP, the primary and secondary DNS
addresses can be learned via the PPPoE protocol. Using
this option provides the advantage that you will not need to
reconfigure the PCs or the iPBX30 if the ISP changes their DNS
addresses.
• Configured on the iPBX30: You can also specify the ISP's DNS
addresses in the WAN configuration page.
Follow these steps to configure DNS relay:
1. Enter LAN IP in the DNS Server IP Address field in DHCP
configuration page.
2. Configure the LAN PCs to use the IP addresses assigned by
the DHCP server on the Internet Security Router, or enter the
Internet Security Router's LAN IP address as their DNS server
address manually for each PC on your LAN.
Note: DNS addresses that are assigned to LAN PCs
prior to enabling DNS relay will remain in effect until
the PC is rebooted. DNS relay will only take effect
when a PC's DNS address is the LAN IP address.
Similarly, if after enabling DNS relay, you specify a
DNS address (other than the LAN IP address) in a
DHCP pool or statically on a PC, then that address
will be used instead of the DNS relay address.
Chapter 6
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