DNS server

Since the RFC prohibits a virtual router from offering additional services when the physical router is not the "owner" of the virtual IP address, the LANCOM DNS server requires special treatment. The LANCOM offers two options.

• The solution which conforms to the RFC works in the DNS forwarder. If an external IP address is entered as primary or secondary DNS server, then forwarding to the responsible virtual router functions automatically using the ICMP redirect treatment since the packet is simply forwarded to the virtual router. However, if no address is entered and no connection has been made to the remote station to which the packet should be forwarded, then the DNS forwarder checks to see if a virtual router is connected to the remote station.
  • If this is the case and the LANCOM is also the master for one of the virtual routers, then the connection is established and the packet is forwarded to the DNS server assigned to this connection.
  • If the LANCOM is not the master for all connected routers, then the packet is forwarded to the master of the first connected router.
  Note: This procedure only works when all routers behave in accordance with the RFC and use port forwarding. If all of the routers involved are LANCOM devices, then this requirement is fulfilled.
• With the second option, a virtual router reacts to DNS requests itself.
  • In order to enable this behavior, the option 'Internal Services' must be enabled. The LANCOM accepts the requests to the internal services (here, for example, DNS) via the virtual addresses as if it had been addressed through one of the physical addresses.
  • In the default setting (Off) the LANCOM behaves in accordance with the RFC and drops the corresponding packets.
  • The default setting is 'On'.
  If a virtual router is connected to the default route when using the internal services, then this will be assigned by the LANCOM DHCP server as the DNS server. If more than one virtual router is connected by the default route, then the router with the highest priority will be assigned (as is the case with gateway addresses).
  Note: This option can only guarantee trouble-free operation if all of the routers involved are LANCOM devices.