Hello Daniel, Thanks for your reply. I did some debugging, I found that I am getting error like this, earlier this log was in DBG mode, changed to error and then I ran the load.. "auth:pre_auth: Invalid nonce value received (ret 2)" Problem is that this issue getting simulated every time. I am using auth module version of kamailio 4.1.5 , since I checked with latest kamailio version 4.3.2 , I didn't find any differences in this module. Please find my finding below Auth/nonce.c:check_nonce() b_nonce2_len=calc_bin_nonce_md5(&b_nonce2, cfg, secret1, secret2, msg); if (!memcmp(&b_nonce.n.md5_1[0], &b_nonce2.n.md5_1[0], 16)) // here where condition is getting failed and it is returning 2. Regards Surendra Hello, are there any error messages in the syslog? Maybe setting debug level for auth modules to 3 and looking at logs will help to reveal what is happening. Be sure syslog is in async mode, otherwise it will slow down processing. Cheers, Daniel On 16/10/15 08:42, Surendra.P wrote: