CenturyLink Fiber is a great platform that works very well with both our Hosted system and SIP trunks. Latency is very low, and in general the connection is very stable. We do have one requirement, though, that CenturyLink turn off their SIP ALG which is basically a method of rewriting SIP packets for enterprise networks. Since we already do this internally, this can interfere with our system and cause infrequent periods where an incoming call won't make it through. This happens in cycles of around 60 seconds or so.
To disable this, simply call the number below and request the following after the circuit has been installed, or make sure to work with the provisioning engineer at CenturyLink to disable the following settings as they install. You can also request this on the CenturyLink "Command Central" site where they allow you to enter a ticket.
IP Helpdesk – 877-886-6515 (Option 2)
For CenturyLink Ethernet/Fiber circuits, the following needs to happen:
[edit security]
+ alg {
+ dns disable;
+ ftp disable;
+ h323 disable;
+ mgcp disable;
+ msrpc disable;
+ sunrpc disable;
+ rsh disable;
+ rtsp disable;
+ sccp disable;
+ sip disable;
+ sql disable;
+ talk disable;
+ tftp disable;
+ pptp disable;
+ }
[edit security zones security-zone untrust]
- screen untrust-screen;
Qwest@155-BELLE-WA-I# commit and-quit
commit complete
Migrated from Confluence on 2026-02-03
Original Confluence Article