Remote Ua Behind Nat; Sip Signaling Messages - AudioCodes Mediant 4000 SBC User Manual

CHAPTER 13 Network
Parameter
'Target Start Port'
target-start-
port
[NATTranslation_
TargetStartPort]
'Target End Port'
target-end-port
[NATTranslation_
TargetEndPort]

Remote UA behind NAT

This section describes configuration for scenarios where the device sends signaling and media
packets to a remote UA that is located behind NAT.

SIP Signaling Messages

By default, the device resolves NAT issues for SIP signaling, using its NAT Detection mechanism.
The NAT Detection mechanism checks whether the endpoint is located behind NAT by comparing
the source IP address of the incoming UDP/TCP packet (in which the SIP message is received)
with the IP address in the SIP Contact header. If the packet's source IP address is a public address
and the Contact header's IP address is a local address, the device considers the endpoint as
located behind NAT. In this case, the device sends the SIP messages to the endpoint using the
packet's source IP address. Otherwise (or if you have disabled the NAT Detection mechanism),
the device sends the SIP messages according to the SIP standard (RFC 3261), where requests
within the SIP dialog are sent using the IP address in the Contact header and responses to
INVITEs are sent using the IP address in the Via header.
If necessary, you can also configure the device to always consider incoming SIP INVITE
messages as sent from endpoints that are located behind NAT. When this is enabled, the device
sends responses to the INVITE (to the endpoint) using the the source IP address of the packet
(INVITE) initially received from the endpoint. This is useful in scenarios where the endpoint is
located behind a NAT firewall and the device (for whatever reason) is unable to identify NAT using
its regular NAT Detection mechanism. This feature is enabled per specific calls using the 'Always
Use Source Address' parameter in the IP Groups table (see
is disabled, the device's NAT detection is according to the settings of the global parameter, 'SIP
NAT Detection' parameter (see below procedure).
➢
To enable the NAT Detection feature (global):
1. Open the Transport Settings page (Setup menu > Signaling & Media tab > SIP Definitions
folder > Transport Settings).
2. From the 'SIP NAT Detection' drop-down list (SIPNatDetection), select Enable:
3. Click Apply.
Defines the optional starting port range (0-65535) of the global
address. If not configured, the ports are not replaced. Matching
source ports are replaced with the target ports. This address is set in
the SIP Via and Contact headers and in the 'o=' and 'c=' SDP fields.
Defines the optional ending port range (0-65535) of the global
address. If not configured, the ports are not replaced. Matching
source ports are replaced with the target ports. This address is set in
the SIP Via and Contact headers and in the 'o=' and 'c=' SDP fields.
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Mediant 4000 SBC | User's Manual
Description
Configuring IP Groups). If this feature