Hi Daniel, authentication is done in kamailio by querying the asterisk DB. Users appear in the location table, so I am assuming authentication is successful (or could I be wrong?), my modified AUTH code route[AUTH] { #!ifdef WITH_AUTH #!ifdef WITH_ASTERISK # do not auth traffic from Asterisk - trusted! if(route(FROMASTERISK)) return; #!endif #!ifdef WITH_IPAUTH if((!is_method("REGISTER")) && allow_source_address()) { # source IP allowed return; } #!endif if (is_method("REGISTER") || from_uri==myself) { # authenticate requests #!ifdef WITH_ASTERISK if (!auth_check("$fd", "sipusers", "1")) { #!else if (!auth_check("$fd", "subscriber", "1")) { #!endif auth_challenge("$fd", "0"); exit; } # user authenticated - remove auth header if(!is_method("REGISTER|PUBLISH")) consume_credentials(); } # if caller is not local subscriber, then check if it calls # a local destination, otherwise deny, not an open relay here if (from_uri!=myself && uri!=myself) { sl_send_reply("403","Not relaying"); exit; } #!else # authentication not enabled - do not relay at all to foreign networks if(uri!=myself) { sl_send_reply("403","Not relaying"); exit; } #!endif return; } Thanks, Daniel From: Daniel-Constantin Mierla &lt;miconda(a)gmail.com&gt; Sent: Mittwoch, 20. März 2019 14:51 To: Kamailio (SER) - Users Mailing List &lt;sr-users(a)lists.kamailio.org&gt;rg>; Daniel Meyer-Wendt &lt;dmeyer(a)ygomi.com&gt; Subject: Re: [SR-Users] Pseudo-Variable {$au} is NULL Hello, $au should be filled when the authentication is done. Are you doing it in kamailio, or the auth is done by asterisk? Cheers, Daniel On 20.03.19 12:39, Daniel Meyer-Wendt wrote: Hi All, I am updating our Kamailio from 4.0.6 to the latest 5.2.2, we use kamailio as LB in front of two asterisk server. My problem is that during registration forward to the asterisk servers {$au} is NULL This is the code we have, which is the one you find in most documentations $uac_req(furi)="sip:" + $au + "@" + $var(rip); I logged some Pseudo-Variable to see their contents: {$au} NULL {$aU} NULL {$Au} username@domain.com<mailto:username@domain.com> {$fU} username {$oU} NULL {$ru} rU: {sip:domain.com;transport=UDP and ended up doing this which works $uac_req(furi)="sip:" + $fU + "@" + $var(rip); Any idea what could be wrong? Thanks, Daniel _______________________________________________ Kamailio (SER) - Users Mailing List sr-users@lists.kamailio.org<mailto:sr-users@lists.kamailio.org> https://lists.kamailio.org/cgi-bin/mailman/listinfo/sr-users -- Daniel-Constantin Mierla -- www.asipto.com<http://www.asipto.com> www.twitter.com/miconda<http://www.twitter.com/miconda> -- www.linkedin.com/in/miconda<http://www.linkedin.com/in/miconda> Kamailio World Conference - May 6-8, 2019 -- www.kamailioworld.com<http://www.kamailioworld.com> Kamailio Advanced Training - Mar 25-27, 2019, in Washington, DC, USA -- www.asipto.com<http://www.asipto.com>