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 DNS server in the R&S®NC router requires special treatment. The device 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 site to which the packet should be forwarded, then the DNS forwarder checks to see if a virtual router is connected to the remote site.
- If this is the case and the device 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 device is not the master for all connected routers, then the packet is forwarded to the master of the first connected router.
Important: This procedure only works when all routers behave in accordance with the RFC and use port forwarding. If all of the routers involved are R&S®NC 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 R&S®NC device 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 R&S®NC behaves in accordance with the RFC and drops the corresponding packets.
- The default setting is On.
Important: This option can only guarantee trouble-free operation if all of the routers involved are R&S®NC devices.
