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When to use host headers for multiple sites? - 17.Feb.2003 11:04:00 PM

AxleMunshine

Posts: 63
Joined: 13.Jul.2001
Status: offline

Hi,

I've seen a few posts about host headers and publishing multiple sites on a same IP with ISA.

But, I was wondering why we need to use host headers. If someone can explain, please do.

Here's something I tried. I have a multi-homed SBS server with IIS on the ISA Server (I am too broke for a second server, but it's coming!) and the setup follows the guidelines found in this site. I publish many web sites. The way to do it on a such a setup is to define sites in IIS using other ports than 80 (I usually use 12345) for the site. Then in ISA, the publishing rule redirects the request to the NAT address of the web site using the port used in ISS. This works fine. I even defined multiple web sites in IIS using the same IP but different ports. I do not use host headers. Always worked like a charm. This way, I don't have to define add a new NAT address to the server for each site on the internal side.

However, I was at one point where I got sick of adding new using multiple external IPs for each web site. I wanted to save some IPs! I told myself, heck, ISA uses FQDN for web publishing. Why not use the same external IP address for every site, since ISA redirects requests base on the address name?

I tried that with 2 sites. So, the setup is pretty simple:
- ISA listens on a single IP on port 80 for these two sites
- 2 publishing rules redirect each FQDN to the same internal IP, but with 2 different ports

I restarted the services and one of the sites was answering correctly to the outside and the inside. The other site was answering correctly to the outside, but not to the inside. It was perfect for the outside in both cases (without host headers). If the second site had worked internally, it would have been perfect, without using host headers.

I added host header definitions in IIS and clicked the host header checkbox in ISA's publishing rules. Then I restarted the services and got an error. I rebooted the server and everything is now perfect for the outside and the inside.

Sometimes, when resarting ISA (it rarely happens) after making changes, services will not restart and a RPC error shows up. In these cases I need to reboot. So, I am not sure the site wasn't responding internally because of missing headers or because there was a problem with the services.

I wonder if the host header option is really required??? If ISA uses FQDN and each IIS site has a different IP/port, why would host headers by required?

Thanks in advance,

Axle

Post #: 1

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RE: When to use host headers for multiple sites? - 18.Feb.2003 3:12:00 AM

tshinder

Posts: 47669
Joined: 10.Jan.2001
From: Texas
Status: online

Hi Axle,

Host headers aren't required, but you did run up against the limitation of using ports. While the alternate port numbers are transparent to external users, internal users do need to type the port in the URL.

HTH,
Tom

(in reply to AxleMunshine)

Post #: 2

RE: When to use host headers for multiple sites? - 18.Feb.2003 5:02:00 PM

AxleMunshine

Posts: 63
Joined: 13.Jul.2001
Status: offline

Hi Tom,

thanks for the answer. It conforts me to see I understand how things works.

On the other hand, it now works without supplying the port in the URL. This is because the local DNS resolves the FQDN to the external IP (which is shared). Since ISA does the external address to internal address/port mapping, I should not have to supply the port number. Usually, with web sites behind ISA, IPs need to be resolved to the internal NAT address. However, with web sites on IIS on the ISA Server, the DNS supplies an external IP.

Because of this, am I right in assuming I could still go without the host headers?

With your answer, I also still wonder what situation would need to use host headers? I don't see any from my experience.

Thanks again,

Axle

(in reply to AxleMunshine)

Post #: 3