On Sat, 2010-08-07 at 19:12 +0100, Chris G wrote:
I have a Draytek Vigor 2802n ADSL router, a pretty 'normal' router, slightly up-market even.
...
However, when I try and use the Vigor router as DHCP server I get several problems:-
When I boot my desktop machine it complains that it can't resolve its own name (chris). Nothing on the local network is possible to resolve by name. When I do a 'host chris' or anything similar I get a series of messages saying "reply from unexpected source:". DNS queries are being sent to 192.168.1.1 (the router has set itself up as a DNS proxy) but replies appear to be from the real DNS servers at my ISP.
It does seem to me the router is doing something strange here. I would normally expect a DNS proxy to operate a cache which means it has to operate at application level. It has to look into the client requests, check the cache and, for a miss, check the next DNS server in the chain, cache the response and send it to the client.
What your router seems to be doing is more like NAT, i.e. forwarding the packets to the real DNS server, presumably with the router's public address as the source and then, when the reply is received, simply changing the destination address to the private (LAN) address and sending the packet on the LAN.
Regards, Steve.