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High number of DNS requests?

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High number of DNS requests? - 6.Jan.2010 4:57:02 PM   
twnukowski

 

Posts: 3
Joined: 6.Jan.2010
Status: offline
Hi, I'm just starting into some troubleshooting steps to try and pinpoint some internet performance issues with ISA 2006. I started by analyzing the canned reports and found something odd.

First, the background of our setup:
ISA is running a 2 NIC Edge Firewall configuration. It's a DL360 G5, Quad core Xeon with 4GB RAM. We host a dozen sites or so, some of which can be bandwidth intensive (files of 100-200MB being downloaded). We also have Exchange 2007, about 30 iPhone users running Active Sync, and around 10 people working remotely over VPN. Incoming pipe is a dual T1 config @ 3Mb.

I ran a report for December and found an unusually high number of DNS requests. Here is the top 3:

No Protocol Requests % of Total Requests
1 DNS 2127310 33.30 %
2 http 1704194 26.70 %
3 LDAP (UDP) 498474 7.80 %

Thats well over 2 million requests in 31 calendar days. Does this seem abnormally high? I'm trying to pinpoint why the server and internet access seems to crawl. I believe it's due to bandwidth, but want to make sure it's not something else that could be malicious or misconfigured.


Thanks!

Tom
Post #: 1
RE: High number of DNS requests? - 7.Jan.2010 6:30:46 AM   
paulo.oliveira

 

Posts: 3472
Joined: 3.Jan.2008
From: Amazon, Brazil
Status: offline
Hi Tom,

how´s your ISA NICs configured (ip, mask, gw, dns)?

Regards,
Paulo Oliveira.

_____________________________

Microsoft Premier Field Engineer (PFE)
Blog: http://poliveirasilva.wordpress.com/
Twitter: https://twitter.com/poliveirasilva

(in reply to twnukowski)
Post #: 2
RE: High number of DNS requests? - 7.Jan.2010 8:31:28 AM   
twnukowski

 

Posts: 3
Joined: 6.Jan.2010
Status: offline
Hi Paulo,

Here is the config:

Internal - 192.168.xxx.1/24, no gateway. DNS is pointing to our internal AD DC/DNS servers. 192.168.xxx.9, .11, and .13.

External - xxx.xxx.xxx.46/27, gw-xxx.xxx.xxx.33, dns is set to our ISP's DNS servers. There are also 11 additional IP addresses assigned to this connection.

I should also point out, this ISA server is used as our one and only internal GW.

Thanks for your help!

Tom

(in reply to paulo.oliveira)
Post #: 3

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