Disable SIP ALG
An ALG is an 'Application Layer Gateway'. Typically it's software in a router that inspects VoIP traffic and modifies the information inside in order to try and help make VoIP work better. In practice they tend to make things worse. you may end up with one way audio, no audio or be unable to register.
Disabling an ALG on your router may well help with any VoIP problems. Here are some notes on various routers that we've come across:
Technicolor
To completely disable the SIP ALG, you will need to connect via Telnet to your router. connection unbind application=SIP port=5060 saveall exit
Billion 7800
- Click on ADVANCED, then CONFIGURATION
- Click on VIRTUAL SERVER
- Click on ALG
- Select DISABLE
- click on APPLY, then click on SAVE CONFIG
Neatgear
From Wan Setup Menu: go to NAT Filtering and uncheck the box next to "Disable SIP ALG"
Vigor2750, Vigor2130
telnet in and:
kmodule_ctl nf_nat_sip disable kmodule_ctl nf_conntrack_sip disable
Vigor2760
In the web interface, under Network > NAT, click the ALG tab then set the SIP ALG off
TP Link
telnet in to the router and:
ip nat service sip sw off
If SIP ALG is disabled successfully, it will show Nat Sip v2 switch off! This will reset when rebooted and will need to be set again.
More info:
- More info on: VoIP-Info