ISA Firewall Tools: The DNS Cache Tool

The ISA Firewall resolves names on behalf of Web proxy and Firewall clients. When the ISA Firewall resolves names for these clients, it caches these entries for six hours. Some ISA Firewall admins might have problems with accessing certain Internet sites that change their IP addresses more frequently than every six hours (typically small business sites that use DDNS services for name resolution).

One way to dump the DNS cache on the ISA Firewall is to restart the Firewall service, but there should be a less disruptive way to remove old entries from the DNS cache. The solution is the ISA Firewall DNS Cache Tool.  You can download the DNS cache tools at:

For example, if you want to delete the DNS cache entry for, you would enter:

dnstools /C /SN




Email: [email protected]

MVP — Microsoft Firewalls (ISA)

About The Author

Leave a Comment

Your email address will not be published. Required fields are marked *

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.

Scroll to Top