what does %1, %2 mean in dial plan rule?
The characters between the round brackets on the right side of equal sign in the matching patterns will be put in a buffer.
To refer to the n-th brackets buffer, use %<digit> (for example %1, %2 ...)
For example:
--------------------------In the above dial plan rule,
[Matching Pattern:]
$request = ^INVITE
To = sip:(.+)@
$alias.lookup("%1") = (.+)
[Deploy Pattern:]
To = sip:%2@
---------------------------
%1 refers to the content in the first brackets on the right side of equal sign in the matching patterns,
which is the brackets at line To = sip:(.+)@ in matching patterns.
%2 refers to the content in the second brackets on the right side of equal sign in the matching patterns,
which is (.+) in the $alias.lookup("%1") = (.+)