NEC Univerge SV9100 Manual page 439

Issue 2.0
The green arrow in the diagram above represents the data packets leaving the IP
phone destined for the SV91000 on the Headquarters LAN. The firewall on the
Headquarters network is not configured to recognize the UDP ports used by the
NEC equipment thus blocking them from resulting in registration failure. To solve
this issue the ports used by the NEC VoIP equipment must be opened in the
firewall allowing the NEC traffic to pass through onto the SV9100.
The ports that are required open on the Headquarters location are 5080 (UDP) for
signaling and the voice ports which depend on how many IPLE ports are installed.
IPLE UDP Ports : 10020~10531

The ports that need to be opened on the Remote network are 5060 (UDP) for
signaling and ports 3462 and 3463 for voice (UDP).
VPN
Another common feature is the use of the Internet as the WAN between customer
locations. When this is done VPNs are typically used between the locations. A
VPN (Virtual Private Network) is a private data network that maintains privacy
through the use of tunneling protocols and security features over the public
Internet. This allows for remote networks (with private addresses), residing behind
NAT routers and/or firewalls, to communicate freely with each other. When
building the VPN tunnels, throughout the network, they must be assigned as a
fully meshed network. This means that every network is allowed direct connection
to each and every other network in the topology. Network equipment limitations
may sometimes restrict this ability resulting in no voice path on VoIP calls
between sites. When this happens Peer-to-Peer must be disabled in the SV9100.
The downside to disabling Peer-to-Peer is using more DSPs and consumption of
additional bandwidth at the MAIN location.
8-48 IP Multiline Station (SIP)