Hello, I tried to understand the concept of first hop in "replies" In the documentation ; For incoming SIP replies, it means that top Record-Route URI is 'myself' and source address is not matching it (to avoid detecting in case of local loops). Note that it does not detect spirals, which can have the condition for replies true also in the case of additional SIP reply receival. Here's an incoming reply received on 217.112.180.10. Via: SIP/2.0/UDP 217.112.180.10;branch=z9hG4bK723f.db3510ce15ac9bb6467e115ecc2fe2a7.0. Via: SIP/2.0/UDP 217.112.180.9;rport=5060;branch=z9hG4bK723f.741041093fec570744afcf44f2194581.0. Via: SIP/2.0/UDP 217.110.38.229:5060;rport=5060;branch=z9hG4bK0eB7070489d338025ed. Record-Route: <sip:217.112.180.9:5060;lr=on;ftag=7B84E4CBh3;did=4cf.c94;nat=yes>. Record-Route: <sip:217.112.180.10:5060;lr=on;ftag=7B84E4CBh3;did=4cf.448>. The Record-Route is 217.112.180.9 but the first proxy is 217.112.180.10.