DNS problem on cisco router

nitsg.gupta · ‎10-24-2009

Hi All,

i have a small network in which i have a router connected to a switch and all the hosts are connected to the switch in different vlans. router is acting as a L3 device to make communication possible between vlans.

problen is that when i ping ip address of google.com it pings but if I try to ping google.com from router, switch and PC it doesn't ping hence i cant browse the internet from my PC.

all the PCs are getting its ip address and other info from dhcp configured on cisco router.

and i've also configured the router for NAT.

what could be the problem.

plz help....

francisco_1 · ‎10-24-2009

Couple of thing to check...

Is the router issuing default gateway address to your hosts?

Does the router have a route to the internet?

nitsg.gupta · ‎10-24-2009

thanks for quick reply

yes, default route is configured thats y i m able to ping WAN ip address.

problem is only with fqdn or browsing.

Reza Sharifi · ‎10-24-2009

Nitin,

You need to configure the IP address of the name server

for example:

ip name-server 192.168.1.100

You also need to enable

ip domain-lookup

This command is enabled by default, but lots of operators disabled it.

HTH

Reza

nitsg.gupta · ‎10-24-2009

i have already configured above commands but still in trouble.

francisco_1 · ‎10-24-2009

you mentioned you can ping google ip from hosts but cannot access google web page?

nitsg.gupta · ‎10-24-2009

exactly..

francisco_1 · ‎10-24-2009

try enabling dns server on router and use 194.72.6.51 (This is a DNS server on the net)

dns-server 194.72.6.51

or setup dns manaully on a host and try it..

nitsg.gupta · ‎10-24-2009

i m using ISP dns and internet dns which is 4.2.2.2

francisco_1 · ‎10-24-2009

if you can ping but unable to bring up a web page sounds like dns resolution to me. do you wanna try the dns i gave you!

Reza Sharifi · ‎10-24-2009

Can you ping the DNS server (4.2.2.2)?

nitsg.gupta · ‎10-24-2009

some one blocked UDP port no 53 for some R&D. now users can browse the internet.

thank you very much for your time and help.

francisco_1 · ‎10-24-2009

ha!. Good to know problem is solved. :)