Technical Tip: How to confirm if FortiGate is using SIP Session Helper or SIP ALG
Products
FortiGate
FortiGate v5.2
Description
This article explains how to confirm if SIP traffic is being handled by SIP ALG or by SIP Session Helper.
Solution
By default, FortiGate is using SIP ALG to process SIP traffic.

To verify it checking configuration and counters:
Show full system settings | grep default-voip-alg-mode
FGT2 # show full system setting | grep default-voip-alg-mode

#set default-voip-alg-mode proxy-based

Proxy-based – default SIP ALG mode
Kernel-helper-based – SIP session helper

To verify counters based on the mode:

1) If SIP Sessions Helper is handling the SIP traffic, the command below will display counters:
#diagnose sys sip stat
FW80CM3912****** # diagnose sys sip status
dialogs: max=65536, used=0
mappings: used=0
dialog hash by ID: size=4096, used=0, depth=0
dialog hash by RTP: size=4096, used=0, depth=0
mapping hash: size=4096, used=0, depth=0
count0: 0
count1: 0
count2: 012
count3: 0
count4: 0


2) If SIP ALG is handling the SIP traffic, the command below will display counters:
#diag sys sip-proxy stat
FW80CM3912****** # diag sys sip-proxy stat
sip stats
vdom name: root
---------------------------
     active-sessions: 0
     calls-attempted: 0
     calls-established: 0
     calls-failed: 0
      calls-active: 0
     registers-active: 0
              |     received  |     blocked   |  unknown form |  long headers
     req-type |    req    resp|    req    resp|    req    resp|    req    resp
     UNKNOWN         0       0       0       0       0       0       0       0
     ACK             0       0       0       0       0       0       0       0
     BYE             0       0       0       0       0       0       0       0
     CANCEL          0       0       0       0       0       0       0       0
     INFO            0       0       0       0       0       0       0       0
     INVITE          0       0       0       0       0       0       0       0
     MESSAGE         0       0       0       0       0       0       0       0
     NOTIFY          0       0       0       0       0       0       0       0
     OPTIONS         0       0       0       0       0       0       0       0
     PRACK           0       0       0       0       0       0       0       0
     PUBLISH         0       0       0       0       0       0       0       0
     REFER           0       0       0       0       0       0       0       0
     REGISTER        0       0       0       0       0       0       0       0
     SUBSCRIBE       0       0       0       0       0       0       0       0
     UPDATE          0       0       0       0       0       0       0       0
     PING            0       0       0       0       0       0       0       0
     YAHOOREF        0       0       0       0       0       0       0       0
 FW80CM3912****** #
Last Modified Date: 09-10-2019 Document ID: FD38087