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New Member

HTTP Probe and DNS names

Hi,

I think i have a very simple question.

I want to setup an HTTP probe to test for URL, like http://www.cnn.com/

When I specify such "request" command under probe confif menu, I would assume that ACE will need to perform name resolution for www.cnn.com, but I cannot find any reference on how to configure DNS servers on ACE....

Am I missing something, or maybe I cannot do HTTP probe request by name and it had to be in a format of

http://<ip address/?

Thank you,

David

5 REPLIES

Re: HTTP Probe and DNS names

Hi,

By default, the probe uses the IP address from the real server or server farm configuration for the destination IP address. (Although you can override this with the ip address command.)

The probe request URL doesn't include a domain name - just a path (and a method), something like "/digital/media/graphics.html" hence there is no need to configure a dns server.

HTH

Andrew.

New Member

Re: HTTP Probe and DNS names

Hi,

Ok, let me better explain what we have.

We have a serverfarm that runs web services with multiple websites hosted on the same servers. Example being http://www.abc.com and http://www.xyz.com. All sites share SAME IP address and the decision which content to present is based on HTTP headers.

When I configure HTTP probe for those I would like to make sure that I get proper HTTP response code (200-399) from each of the websites before ACE forwards the request.

I accomplished that on CSM by using HTTP probe and specifying the URL itself. Unfortunately i do not see such option in ACE :-(

If I test for "/something/index.html" it will be the same for all websites....

So i was wondering if it's possible to duplicate what I had done in CSM?

Thanks!

David

Cisco Employee

Re: HTTP Probe and DNS names

switch/Admin(config-probe-http)# header Host ?

header-value Specify probe http header value

switch/Admin(config-probe-http)# header Host

New Member

Re: HTTP Probe and DNS names

Hi,

My initial idea was to use the following command:

request method get url http://www.abc.com/

This is why I had my initial question about how will ACE resolve www.abc.com

Now thinking more about it I wonder if ACE even needs to resolve it at all.

I intend to apply the probe under rserver in serverfarm config, so ACE will know the IP address of where to send the probe from rserver configuration. If so, no DNS query is needed. ACE will just construct the packet and put relevant information in HTTP portion.... Am I correct?

If yes, what would be a difference is doing

header Host header-value "http://www.abc.com/"

vs

request method get url http://www.abc.com/

Thanks!

David

Cisco Employee

Re: HTTP Probe and DNS names

First the header command would be :

header Host header-value "www.abc.com"

So no http://

The difference between the 2, is that with the header value, the request will look like this :

GET / HTTP/1.1

Host: www.abc.com

With the other option using the request http://, the http request will look like this

GET http://www.abc.com HTTP/1.1

Host: 1.1.1.1

A normal request is the first one.

The 2nd type of request is used when going through proxies.

So, I'm sure the first one will work.

The 2nd could also work as well.

And indeed there is no need for name resolution here.

Gilles.

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