I try replace info PAI header by using subst() function in route block as below: route[3] { ... $var(fromU) = 22227777; ... subst('/^P-Asserted-Identity:(.*)sip:[^@]*@([a-zA-Z0-9.:]+)( .*)$/P-Asserted-Identity:\1sip:$var(fromU)@\2\3/ig'); ... ... forward(); exit; } but when I read ngrep command output I catch P-Asserted-Identity header as below: +++++++++++++++++++++++++++++++++++++++++++++++ before route[3] processing: INVITE sip:99992222@15.113.132.21:5060 SIP/2.0. ... P-Asserted-Identity: "Display Name 7777" <sip:7777@101.14.101.245>. ... +++++++++++++++++++++++++++++++++++++++++++++++ after route[3] processing: INVITE sip:99992222@15.113.132.21:5060 SIP/2.0. ... P-Asserted-Identity: "Display Name 7777" <sip:22227777@101.14.101.245>.P-Asserted-Identity: "Display Name 7777" <sip:7777@101.14.101.245>. ... +++++++++++++++++++++++++++++++++++++++++++++++ Is it normal or bug behaviors? Regards CMA