Cisco IOS as DNS Server

Unanswered Question
Apr 10th, 2007

Hi,

I was wondering if Cisco IOS can provide basic DNS services or DNS forwarding. I know IOS can be set up as a DHCP server, but can IOS be a basic DNS server as well?

Any help or insight would be appreciated!

Thank you.

I have this problem too.
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Collin Clark Thu, 04/12/2007 - 08:38

Sure, it's called DNS Proxy. It's not supported on all devices, so you'll have to check.

http://www.cisco.com/univercd/cc/td/doc/product/software/ios123/123relnt/800/rn830xc3.htm

DNS Proxy

In virtual private network (VPN), Point-to-Point Protocol over Ethernet (PPPOE), etc. PCs connected to the LAN may get Dynamic Host Configuration Protocol (DHCP) parameters including the IP addresses of the Domain Name System (DNS) server prior to the router connecting to the WAN to get the information over IP Control Protocol (IPCP). The objective with Proxy DNS (or caching-only name server) enables the router to receive DNS queries on behalf of the real DNS servers and proxy for the hosts on the LAN connected users. This enables the DHCP server to immediately send the hosts the router's own LAN address in lieu of the DNS server's IP address. The router forwards the DNS queries from local users to real DNS servers after the WAN connection comes up and caches the DNS records in response. Over the time, cache includes the DNS information most often requested by the local resolvers and this can reduce the overhead of packets to the WAN.

The router must obtain the correct DNS server information from the WAN in order for it to function as a proxy DNS server.

The global configuration command ip dns server enables DNS proxy server functionality on the router, and causes it to forward DNS queries to the actual DNS servers. The global configuration command dns-server address causes the router to respond to DNS queries with its own IP address.

HTH and please rate.

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