sip:response rewrite

Hi all, We have configured an irule that intercepts sip response and if the sip response code is equal to 503, it has to rewrite 503 in 500 and send it to outside of F5.

 

when SIP_RESPONSE {

 

if { [SIP::response code] == "503" } { SIP::response rewrite 500 "Service Unavailable" log local0. "After rewrite: [SIP::response code]" } }

 

In the ltm log, we have observed that the response code after the rewrite is actually 500, but analysing the tcpdump, to outside of F5 it is send 503.

 

How is it possible?

 

Regards