slow dns with debian lenny & windows 2008 dns servers

[mbentley]

so i have an odd problem that i haven't been able to resolve in quite some time. i have a debian lenny laptop that uses my windows 2008 dns servers and the dns resolution can take anywhere from 4-7 seconds in firefox. nslookup seems to be instantaneous. from what i have read, many people have this problem but it is related to ipv6, however i have disabled it.

if i change my dns servers to point to my router, opendns or google dns, everything works fast so it seems that i has to be something with my window 2008 dns server. has anyone ever seen this before or know how to fix it? i've tried to set my dns servers to point to open dns and google dns and that didn't help either. i also noticed that dns lookups are slow no matter if they are addresses that are on my internal network or external to my home network.

any ideas at all? i'm absolutely out of ideas.

[kaltag]

Couple of things. Is the 2008 box using DNS forwarders or root hints? I've also had issues if autotuning is enabled on the NIC on the 2008 box with DNS and DHCP timeouts. I can't remember the command on the top of my head but it shouldn't be too had to find. If neither resolves the issue you could try a simple DNS service like dnsmasq. Install it on the linux box and configure it's forwarders to the 2008 box and an external DNS of your choice and configure your linux box to use itself for DNS.

[mbentley]

Couple of things. Is the 2008 box using DNS forwarders or root hints? I've also had issues if autotuning is enabled on the NIC on the 2008 box with DNS and DHCP timeouts. I can't remember the command on the top of my head but it shouldn't be too had to find. If neither resolves the issue you could try a simple DNS service like dnsmasq. Install it on the linux box and configure it's forwarders to the 2008 box and an external DNS of your choice and configure your linux box to use itself for DNS.

my 2008 dns servers are set up to use forwarders. i'll have to do some searching for what you mean about the autotuning settings. i've thought about setting up a local dns service but i figured i'll set that as a last resort as i still think i would run into the same problem when it is looking up a site that isn't cached.

another thing i have read about is messing with the hosts settings of /etc/nsswitch.conf, once again something i will have to read into more. the default settings are:

# /etc/nsswitch.conf
#
# Example configuration of GNU Name Service Switch functionality.
# If you have the `glibc-doc-reference' and `info' packages installed, try:
# `info libc "Name Service Switch"' for information about this file.

passwd: compat
group: compat
shadow: compat

hosts: files mdns4_minimal [NOTFOUND=return] dns mdns4
networks: files

protocols: db files
services: db files
ethers: db files
rpc: db files

netgroup: nis

[kaltag]

Sorry it took me a bit to find the right article but here it is. The article discusses what it is and how to turn it off.

http://www.mydigitallife.info/2007/03/22/disable-tcp-auto-tuning-to-solve-slow-network-cannot-load-web-page-or-download-email-problems-in-vista/

The symptoms and instructions apply to server 2008 as well. We had tons of networking issues on a couple 2008 boxes with this enabled.

[mbentley]

thanks for looking that up for me. i will try to disable it and see if the dns resolution speed improves.

[mbentley]

just to update, after doing that, it seems like it might be a little bit better (like the delay was cut in half or so) but still not quite where i expect it to be. another place for me to look will be the fact that i am on wireless. for all i know, there is some sort of issue with the wireless drivers. i'll have to check using a wired connection to see if there is a difference there.

[{PMS}fishy]

2008 or 2008 r2?

Maybe it is an eDNS issue.

http://weblogs.asp.net/owscott/archive/2009/09/15/windows-server-2008-r2-dns-issues.aspx


Fix

To disable EDns, you can do it from the command prompt, or by editing the registry.

From the command prompt, no restart of DNS is required. If from the registry, make sure to restart the DNS Server service.

Command prompt:
dnscmd /config /EnableEDNSProbes 0

No restart is needed. It takes effect immediately.

or Registry: </>
Create a DWORD called EnableEDNSProbes and set to 0 in HKLM\SYSTEM\CurrentControlSet\services\DNS\Paramet ers

Restart the DNS Server service for it to take effect.

[mbentley]

i'm just using 2008 (not r2)

[{PMS}fishy]

i'm just using 2008 (not r2)

Never mind then. It is only related to R2.