Change DNS to multiple Client Machines

[techjoe.2]

Hi All,

I have a scenario

A Cisco 2900 Router connected to Internet

A Catalyst Core Switch configured with all VLANs

Access Switches connected to End devices

Now the client machines are configured with Local DNS (the DC Address), DNS for Internet.

Now say if my DNS for Internet is down for some reason, what is the best way to change it so that it is reflected to all the client machines.

My idea is to use ip name-server on the Router and change it something like 8.8.8.8. But is there a better and an accepted way of doing it? Please provide me your valuable answers

[balaji.bandi]

If the router internet fails, even google DNS  not reachable, I do not see any solution here. until you have 2 different links to the Internet, in that case, your DNS still works on the route.

i suggest having a local DNS that is in your control. if you like you can use Google DNS.

[Georg Pauwen · Accepted solution]

Hello,

not sure I understand what you are asking...if the Google DNS server is down (which never happens anyway) or unreachable, you want to use a local DNS server ?

Are you using a DHCP server ? If so, most DHCP servers can assign primary and secondary DNS server addresses to the clients.

You could even use the Cisco router as DHCP server, and assign multiple DNS servers, which will be called in order:

ip dhcp pool LAN

network 192.168.1.0 255.255.255.0

default-router 192.168.1.1

dns-server 8.8.8.8 192.168.1.1

[techjoe.2]

Thanks for the solution, Do we mention the DNS provided by the ISP on the DHCP options?

[Georg Pauwen]

Hello,

that is an option. You can add the ISP provided DNS server, the DNS servers will be called in sequence.

[techjoe.2]

Thank you for the answer

[johnlloyd_13 · Accepted solution]

hi,

the 'ip name-server' is only for doing local DNS on the router itself, i.e. ping to google.com instead of an IP.

are you doing DHCP on the router, switch or on a separate server? i suggest adding a tertiary DNS for Internet name translation and push the policy to your client machines.

[techjoe.2]

Thanks for the answer, does the ip name-server specify the DNS, so that when client traffic hits the router it uses it for name resolution?

Where do we setup the tertiary DNS? on the Windows server?