Given a network with multiple VLANs and a single DHCP/DNS server is it possible to have multiple addresses for a single DNS server so each subnet looks like this:
10.10.20.0 with
default gw = 10.10.20.1
dns server= 10.10.20.1
10.10.21.0 with
default gw = 10.10.21.1
dns server= 10.10.21.1
While the actual DNS server resides at 10.10.20.100
I've very recently learnt the 3550 does not support NAT/PAT - which was how I planned to achieve this
The DHCP server can issue addresses with 10.10.20.100 as the DNS server and the requests are routed/allowed ok in our config, but we have a room full of training PCs with the DNS server statically defined as 10.10.21.1. The basic router (I guess the clue to me is in the name) which put the training room on a different subnet before buying the Cisco kit managed to forward the DNS requests from clients via 10.10.21.1 on to our DNS server - am I missing something obvious as a solution to this?
The PCs are regularly restored from images after courses have run so it's more of a headache to change the client PCs DNS server address in this case. If we do go down that route I would have them assigned static addresses via a hosts entry in DHCP server making life easier in the future.
We have an 877 router and 3550 switch - I started to consider there might be an answer by routing traffic back to the 877 to receive its routing decision but then all the lan traffic would be flowing down a 100Mbs bottleneck. In this sense I guess our problem is worse as the DNS server address is also the same as the default gateway address so I can't extend the VLANs up to the 877 (which currently only knows about the different subnets courtesy of static routes directing it back to the switch)
Alternatively I could put a quad port NIC in the DNS server - one address per port patched back to the different VLANs... but then this address will need to be different from the default gateway... I seem to have gone full circle! If I make the default gateway for each subnet the DNS/DHCP server and manipulate traffic with iptables we have a point of faliure with more moving parts than the Cisco kit and another bottleneck.
Is there a simple solution?
Please :-D
Thanks in advance.
With
