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tomdlgns
Premium Member
join:2003-03-21

tomdlgns to JF05

Premium Member

to JF05

Re: Sonicwall NSA 240 - Intermittent DNS Issues

so it looks like the sonicwall is doing DHCP....

why not use the sonicwall address for the DNS servers on the network?

my NIC settings in the locations that i dont have a DNS server in place and use the sonicwall for DHCP :

ip address- 192.168.1.100
sub- 255.255.255.0
gate- 192.168.1.1

DNS- 192.168.1.1
DNS2- 8.8.8.8.8

sonicwall ip is 192.168.1.1
dhcp range typically starts at .100 and ends at .150

since i only have one sonicwall device, i use the free, public DNS server as a backup. but this would only come into play if the DNS servers provided by the ISP (hard coded in the sonicwall) are down or acting up. then it uses the secondary DNS i provided.

JF05
@comcastbusiness.net

JF05

Anon

Changing to the sonicwalls IP and with the public DNS server as the backup only results in the computer immediately switching to the public DNS server (8.8.8.8) because it doesn't get a response from the sonicwall.

Looking around in wireshark it looks like problems specifically with DNS only arise when the computer attempts the wrong DNS server for the internet connection. In which case the server responds that it is not an authority on the domain and the query is refused. So in general it has to be something else that is causing the congestion which also seems to affect DNS queries intermittently... Other things that have been becoming more apparent are extreme slowness inside the network when dealing with computer names, etc.

My only guess is some piece of hardware is on its way out, and is congesting the network or something is improperly configured causing general network slowness to arise. Last time we had a switch go out that began flooding the network with ARP, but that doesnt seem to be the issue right now...
tomdlgns
Premium Member
join:2003-03-21

tomdlgns

Premium Member

can you give us the output of ipconfig /all on a few workstations?

if all of the NIC cards DNS settings are pointing to the outside (ISP or public DNS), then how is internal DNS supposed to work?

something on your network should be desginated as the DNS server/role/function.

JF05
@comcastbusiness.net

JF05

Anon

It looks like the sonicwall can only forward DNS, so it would appear that yes, our network was set up without an internal dns server. The only thing I cannot explain is why the network worked without one for so long.
tomdlgns
Premium Member
join:2003-03-21

tomdlgns

Premium Member

is sonicwall your DHCP server?

i know i asked above, but lets keep this simple and start over.

if the sonicwall is doing DHCP, you can go in the scope settings and specify the DNS servers you want to use/what the sonicwall pushes out to the LAN.

use the same ip that you are using as the gateway. both gateway and DNS servers should be the inside address of the sonicwall.

i am assuming it is something like 192.168.1.1...10.10.10.1....something like that.

it has been working all this time because DNS is doing its job. you are using an external DNS server to get to your websites. but if you try to do stuff internally, i dont see how your network can match, lets say...server1 with an IP address on your network. since there is nothing telling it what the IP is.

i dont know that this will solve your problem, but i highly recommend that you change your scope options on the sonicwall DHCP settings and get that working properly before moving onto the next issue, assuming there is still an issue.

i'd also recommend doing ipconfig /flushdns on all the machines on the network after they have gotten the new DHCP info from the sonicwall.