IP DNS server configuration in ASR 1006

[niral.damania]

Hi,

I have a ASR 1006 router in my environment and I want to make it a DNS server for some reason. I tried to configure the command IP dns server on the ASR but it does not accept the command. I also have a Cisco 7206 VXR router in my environment which acepts this command.

The IOS version of my ASR is

IOS-XE Software (PPC_LINUX_IOSD-ADVENTERPRISEK9-M), Version 15.1(3)S2.

Pls guide

Cheers, Niral

[Bilal Nawaz]

Hello Niral,

Please see DNS configuration guide for IOS-XE: http://www.cisco.com/en/US/docs/ios-xml/ios/ipaddr_dns/configuration/xe-3s/asr1000/Configuring_DNS.html It states that 'To use DNS, you must have a DNS name server on your network'

Hope this helps

Please rate useful posts and remember to mark any solved questions as answered. Thank you.

[Steve Fuller]

Hi Niral,

Unfortunately Cisco IOS XE currently only supports DNS resolver i.e., client functionality. The support for DNS server is currently only available in IOS, and not IOS XE. As per the Prerequisites for Configuring DNSin the Cisco IOS XE DNS Configuration Guide:

Prerequisites for Configuring DNS
To use DNS, you must have a DNS name server on your network

Regards

[Richard Merrett]

Hi, I realise this thread is a few years old, but it seems to relate to an issue/question I have on IOS XE on my 4451 ISR router. When I configure my client machines to use the router as the DNS server, name resolution fails. If I configure then to use 8.8.8.8 then everything works fine. So, I seem to have concluded that either the latest version of IOS XE still does not support DNS server functions, or I have some missing config. What is slightly confusing me is that I am able to configure 'ip host' entries on the router, such as 'ip host router.test.com 10.1.1.1' and I can see this in the config. However, since my client machines use 8.8.8.8 as their DNS server, they never see this ip host entry configured on the router. So, how do I configure my client machines to pick up DNS entries for hosts on the local network which are configured on the roter itself? I can't work this out? Also, is there any reason why IOS XE does not support DNS server functions? This seems to be a fairly basic router function, and I was under the impression that IOS XE was the latest and greatest Cisco operating system, and if this is true then why would it not support this? Thanks.

[Bilal Nawaz]

I think IOS XE or not, all you need to do is point your hosts DNS at the router, point the router's DNS server out to e.g. 8.8.8.8. Any local hosts you want to lookup, configure those records on the router. I think I did this before, and in theory it should work.

[Richard Merrett]

Hi, I did try that but it does not seem to work. On the IOS XE router I have configured two name servers (external) and then my clients use the router address as the DNS server, but name resolution fails when I do this. Exactly the same configuration but with the client machines using 8.8.8.8 works fine. As far as I can see DNS is all configured on the router and from the router itself (via telnet) everything works fine, just not from the clients.

i have exactly the same config on a Classic IOS 2951 ISR router and on that machine it all works fine and the clients use the router as the DNS server without issue. But on the 4451 box it doesn't work.

On IOS XE the command 'ip dns server' and 'ip dns orimary' do not work, so I cannot see any way to set the IOS XE device to be authorative for the local domain.

does anyone have this working, with the IOS XE router acting as DNS server for client machines?

[Richard Merrett]

It seems the latest IOS XE now has support for DNS Server functions, and I am able to point my clients to the router and the DNS requests get routed out to the name servers configured on the router. However, one thing I have noticed is thst the router always has an empty DNS cache, so it looks like it forwards every request to the external nameservers. Has anybody else used this new feature and is it possible to configure caching?

[Difan Zhao]

What version are you using? Does "show hosts" return anything? I am not using my router as the DNS server but I allow domain-lookup so if I try to resolve on the router itself I have the cache shown in "show hosts"