Hi Ali, Looking through the source code, its not that the port for I-CSCF is hard coded to 5060, its just that it defaults to 5060 if the following is set in the Kamailio.cfg file: dns_try_naptr=no which we had left it disabled. Well I assumed I had all the DNS worked out, I had NAPTR records set for the P,I and S-CSCF. Looking though the pcscf.cfg there is a setting for NETWORKNAME which is set to ims522.ims.org, and is a separate FQDN from the P,I,S-cscf FQDN’s. I always kept the NAPTR rec for ims522 as the same port of the P-CSCF (pcscf522) in DNS. Two things I needed to fix: 1. Enable the DNS NAPTR lookups: dns_try_naptr=yes 2. Modify the NAPR for ims522 to be that of 4060 Thanks to you and Amar for the pointing to DNS. _Martin From: sr-users &lt;sr-users-bounces(a)lists.kamailio.org&gt; On Behalf Of Ali Shirvani Sent: Tuesday, July 23, 2019 1:40 PM To: Kamailio (SER) - Users Mailing List &lt;sr-users(a)lists.kamailio.org&gt; Subject: [EXT] Re: [SR-Users] P-CSCF and I-CSCF ports Hi Martin, As Amar pointed out it may some DNS configuration. You can check the DNS entry of I-CSCF with: $ dig -t srv <FQDN of I-CSCF> Regards, Ali On Tue, Jul 23, 2019 at 7:15 PM Amar Tinawi <amar.tinawi@gmail.com<mailto:amar.tinawi@gmail.com>> wrote: Hello Martin I think you are missing the DNS part. On Tue, Jul 23, 2019, 5:30 PM Woscek, Martin W. <mwoscek@mitre.org<mailto:mwoscek@mitre.org>> wrote: Hi IMS users, I can configure the P-CSCF to use 5060, and the I-CSCF to use 4060 and both come up listening to their respective ports when each module is started. But the P-CSCF is hardcoded to use 5060 for the I-CSCF. Before I make code changes to the executable: Is there some additional configuration to allow for me to switch ports? Why is Kamailio IMS hardcoded and why not enforce it at the .cfg load time? Thanks, Martin _______________________________________________ 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 _______________________________________________ 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