**Description** We use below config to test the topology hiding function，when kamailio receive “update” message，doesn't send out，it will send to itself with destination port 5060；

**Troubleshooting** loadmodule "ndb_redis.so" loadmodule "topos_redis.so" loadmodule "topos.so" modparam("ndb_redis", "server", "name=srv8;addr=127.0.0.1;port=6381;db=2") modparam("topos", "storage", "redis") modparam("topos", "db_url", "redis://127.0.0.1:6381/2") modparam("topos_redis", "serverid", "srv8")

-------- Call flow UE-----------------PROXY-------------B2bua invite-------------->|------------------>invite 183<----------------|<------------------183 Prack------------ ->|------------------>Prack 200ok<-------------|<-----------------200ok update1---------->|-------------| |update2<---| 404<---------------|

**update1:** UPDATE sip:atpsh-5fc1a2c3-5749-2@172.18.67.40 SIP/2.0 Via: SIP/2.0/UDP 172.18.67.34:5062;branch=z9hG4bK-15000-1-0 From: tel:+8618768860000;tag=1 To: tel:32001232;phone-context=ims.mnc002.mcc460.3gppnetwork.org;tag=BH83c9DQXKgvp Call-ID: 1-15000@172.18.67.34 CSeq: 1002 UPDATE Allow: INVITE,ACK,OPTIONS,BYE,CANCEL,UPDATE,INFO,PRACK,NOTIFY,MESSAGE,REFER Contact: sip:+8618768860000@172.18.67.34:5062;zte-did=8-11-20481-2871-12-666-65535;Hpt=8ec8_16;CxtId=4;TRC=ffffff-ffffffff;audio;vid ;+sip.instance="urn:gsma:imei:86183004-974965-0";+g.3gpp.mid-call;+g.3gpp.srvcc-alerting;+g.3gpp.pss-srvcc-orig-pre-alerting;+g.3gpp csi-ref="urn%3Aurn-7%3A3gpp-service.ims.icsi.mmtel"

**update2:**

UPDATE sip:172.18.67.50;r2=on;lr=on;ftag=1;did=874.5af1;vsf=BwwcABoAAQcADwAICAYAcAEHMi4xOC42Ny4zNA-- SIP/2.0 Via: SIP/2.0/UDP 172.18.67.40:55067;branch=z9hG4bK296a.feb7a8004f743a745739026289e0010e.0 From: tel:+8618768860000;tag=1 To: tel:32001232;phone-context=ims.mnc002.mcc460.3gppnetwork.org;tag=BH83c9DQXKgvp Call-ID: 1-15000@172.18.67.34 CSeq: 1002 UPDATE Allow: INVITE,ACK,OPTIONS,BYE,CANCEL,UPDATE,INFO,PRACK,NOTIFY,MESSAGE,REFER Max-Forwards: 70 Require: precondition Supported: histinfo,replaces,precondition,100rel,timer User-Agent: IM-client/OMA1.0 HW-Rto/V1.0 P-Access-Network-Info: 3GPP-E-UTRAN;utran-cell-id-3gpp=4600039c6b98855b;network-provided;sbc-domain=luypsbc22bzx.0371.101.ha.chinamobi .com P-Charging-Vector: icid-value=No1ZR2PilD-0000a442-0d-0000816e-001;orig-ioi=chinamobile Content-Type: application/sdp Content-Disposition: session Content-Length: 743 Contact: sip:btpsh-5fc1a2c3-5749-2@172.18.67.50

below ip and port are configured for kamailio; 172.18.67.40:55067 172.18.67.50:5060

**Additional Information** version: kamailio 5.4.2 (x86_64/linux) flags: USE_TCP, USE_TLS, USE_SCTP, TLS_HOOKS, USE_RAW_SOCKS, DISABLE_NAGLE, USE_MCAST, DNS_IP_HACK, SHM_MMAP, PKG_MALLOC, Q_MALLOC, F_MALLOC, TLSF_MALLOC, DBG_SR_MEMORY, USE_FUTEX, FAST_LOCK-ADAPTIVE_WAIT, USE_DNS_CACHE, USE_DNS_FAILOVER, USE_NAPTR, USE_DST_BLACKLIST, HAVE_RESOLV_RES ADAPTIVE_WAIT_LOOPS 1024, MAX_RECV_BUFFER_SIZE 262144, MAX_URI_SIZE 1024, BUF_SIZE 65535, DEFAULT PKG_SIZE 8MB poll method support: poll, epoll_lt, epoll_et, sigio_rt, select. id: compiled on 20:13:39 Nov 9 2020 with gcc 4.8.5