Router as DNS server / forwarder

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Feb 23rd, 2008
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I'm trying to setup my router as a dns server / forwarder, but the manuals are not really helping me out. What I'm trying to accomplish is the following:


The router should function as a DNS server. It should forward domain specific requests for domain1.local to for example 192.168.1.1 (dnsserver for domain1) and requests for domain2.local to 192.168.2.1 (dnsserver for domain2). All the other DNS requests should be forwarded to the DHCP learned DNS server from my ISP.


Any suggestions on how to accomplish this?

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scottmac Sat, 02/23/2008 - 06:11
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Please specify what equipment you are working with.


Cisco routers don't do DNS.


If the domains are on different interfaces, you could (probably) use policy-based routing to direct them to a segment other than the default.


With the information provided, since you (probably) have two different networks, and they are (probably) on different interfaces, then the router will direct that traffic to the different networks based on the address of the destination host anyway ...


A DNS request sent to the .2.1 DNS will by default be sent to the .2.0 network segment. A DNS request sent to the .1.1 DNS will, by default, be sent to the .1.0 network.


There are no un-addressed DNS requests floating around the network , waiting to be plucked out by a router and sent somewhere .... each request would have a (source and) destination address, and that's where the router will, by default, send it.


Policy-Based Routing permits you to look at specific information within the packet and make routing decisions based on that info, and, to some degree, change specific information within the packet.


Good Luck


Scott



2044418Puts Sat, 02/23/2008 - 06:40
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Hi I'm using a 1711 with 12.4(15)T3 IOS. The idea was that all the clients have the router's IP configured as DNS server.


Let's say that the clients are member of domain3.local (192.168.3.x). If they need DNS resolution they go and query the routers DNS. If the router receives a request for domain1.local, then the router should do a recursive or itterative request to the DNS server (a W2k3 server for example) responsible for domain1.local.


Thats what I like to accomplish.


All the segments have their own interfaces, but I'm not sure how policy based routing is going to help me out.

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