CPL Explanation

[JFerello]

Can anyone explain how this CPL works?

I don't understand the first regex in location and the first replace in location either.

<cpl xsi:schemaLocation="urn:ietf:params:xml:ns:cpl cpl.xsd">

<taa:routed>

<taa:rule-switch>

<taa:rule unauthenticated-origin=".*" destination="(.+)@cisco\.com>

<taa:location clear="yes" regex="(?!.*@ciscotp\.com)" replace="\1" source-url-for-message-regex="(.*)@(ciscotp)\.com" source-url-for-message-replace="\1.@\2.net">

<taa:proxy/>

</taa:location>

</taa:rule>

</taa:rule-switch>

</taa:routed>

</cpl>

[Wayne DeNardi]

Often when I want to check what a regex expression is doing if I am uncertain, I use https://regex101.com/.

So, if my interpretation is correct, it's checking for anything that has @ciscotp.com in the address, and then the second part makes it an address with @ciscotp.net instead.

[JFerello]

Wayne,

Thanks for the reply, I totally understand regex as a language, I am getting tripped up on the CPL part though.

For example, in the <taa:location> line there are (4) arguments for something that I would think only needs (2), for a source re-write I would only think you need to match the original source and then have the replacement source.

As for the (4) arguments, what does each one do and why?

1) regex="(?!.*@ciscotp\.com)"

2) replace="\1"

3) source-url-for-message-regex="(.*)@(ciscotp)\.com"

4) source-url-for-message-replace="\1.@\2.net"

[Wayne DeNardi]

Hi Justin, if you haven't sorted the issue yet, there's a CPL Reference in the Expressway Admin Guide (see pages 371-379).

The first regex is a negative lookup - so matches anything that has a location (ie the call destination) that isn't (.*@ciscotp\.com) and the second bit replaces it with itself (essentially leaving it alone).

The third and fourth bits change the source-url for anything that is a domain of ciscotp.com to ciscotp.net,

So, if I interpret it correctly, any calls to a destination that isn't a domain of ciscotp.com will get their source URL re-written to come from the ciscotp.net domain.  Any calls from ciscotp.com will stay as coming from ciscotp.com.