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We are trying to use DynDNS with ISA 2000 but of course we have no idea what ports it rests on. We are not married to DynDns and our DSL modem does not support Dynamic DNS.

Online there are books related to the pairing but no other such information. All we want is an easy way to get the IP address since it changes constantly.

NOTE: According to TCP/View, DynDNS opens a random number of ports numbered 47xx

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Are you properly getting a dynamic IP with the ISA to begin with? – Oskar Duveborn May 15 '09 at 20:58
up vote 2 down vote accepted

The Perform Update section of the DNS Update API says that updates can be performed over HTTP or SSL-encrypted HTTPS (preferred).

The ports used are as follows.

HTTP ports: 80, 8245 
HTTPS port: 443

The update interface listens on ports 80 and 8245 for HTTP, and 443 for HTTPS. Port 8245 may be used to bypass transparent HTTP proxies. It is not necessary to open any incoming ports (or allow incoming ICMP) for updating.

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If I understand correctly, you want to let the DynDNS client update your public IP? For that you just need port 80.

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Was already set open. TCP/View shows DynDNS updater on random ports numbered 47xx, with anywhere between 1-3 processes being spawned. – Terry May 14 '09 at 17:51
That's odd. Are you using the official client? I'm not familiar with the Windows client, but maybe it is trying to get the public IP from several servers. Make it get it from only, and open that port on ISA Server. – Ivan May 14 '09 at 22:22
Yes we are using the official client. It seemed odd to me as well, so we will give what you suggested a shot. – Terry May 15 '09 at 16:35

The way that the DynDNS service works is by hosting the DNS service on their systems while you have a client that updates the record on their systems. There is truly nothing special about the service. If you are trying to determine what your external IP address is, you can always do a DNS query on the hostname you have assigned on the service. If you are not hosting any externally accessible services (such as a web server or VPN), then you could simply use a site that will tell you what your external IP is (or even view the DHCP address on the DSL modem which usually has a web-based interface.)

Off-topic: If you are doing any kind of serious hosting of services, I'd highly recommend either changing to a static IP service with your ISP, or for just web hosting, outsourcing to a dedicated hosting service.

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DynDNS and no-ip allow you to install a very lightweight client application on any machine on your network and it will update DNS for you as well.

The feature does not need to be built into the router.

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