DHCP Gateway and DNS

Cisco 877 security bundle with plus feat...
June 29, 2010 at 23:07:03
Specs: Windows 7
I am just confused on the DHCP or the router setup. I setup the DHCP on the router and set the DNS server same with the ISP. The senior engineer said that I should setup the DNS server and the gateway with the same IP address. He said that the router has cache so any DNS resolve is save on the cache and it will save some bandwidth since the router will not forward all of the DNS resolution to the ISP DNS servers. Is this true or not? I am just confused because normally we put the DNS server of the ISP on the DHCP configuration of the router.

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#1
June 30, 2010 at 02:12:40
Yes, that's how DNS is designed to work. It will cache the upstream server's response for quicker replies.

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#2
June 30, 2010 at 06:34:33
So it means that it is recommended that if I configure DHCP server in the router, the gateway and the DNS server should be the same.

Is this the recommended one?

ip dns server
!
ip dhcp pool jeff
network 192.168.1.0 255.255.255.0
default-router 192.168.1.254
dns-server 192.168.1.254
!
ip name-server 4.4.4.4
ip name-server 4.4.4.2


I hope for your reply.


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#3
June 30, 2010 at 08:42:19
Any reason you are using Verizon's dns servers and not your isps?

"dns-server" I don't recognize this as a cisco command but it could just depend on IOS version.


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Related Solutions

#4
June 30, 2010 at 09:53:50
Sorry I just don't want to put the dns of my ISP. My main
concern is to make if my question is true. If you configure the
dns with the same ip of the router, you are saving bandwidth
because the router will not always forward the dns query to
your ISP for the same site because it will save it on it's cache.
I think also the command is correct for the cisco 877.

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#5
June 30, 2010 at 10:06:48
How many users on the lan side accessing the internet?

Under 50 I wouldn't bother.

configuring as a dns caching server takes resources on the router. DNS queries don't take a large amount of bandwidth and once resolved the local workstations dns cache contains the entry for next time.


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#6
June 30, 2010 at 13:50:54
It's more than 50 and the Internet bandwidth is 4mb. I was
thinking about that but my senior and my manager is saying
that many dns queries eats up bandwidth. I just didn't argue
for I might losing my job. I post it here to check if my idea is
corect and I think i am right that dns queries don't eat up
bandwidth.

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#7
June 30, 2010 at 14:46:21
Might as well do what they ask. I wonder if they know about the local MS DNS resolver cache.

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#8
June 30, 2010 at 21:22:12
Thanks for clearing up my mind.

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