Grandstream Networks WP820 Administration Manual page 34

Network Settings
Outbound Proxy Configures the IP address or Domain name of the Primary Outbound Proxy,
Media Gateway, or Session Border Controller. It's used by the phone for Firewall
or NAT penetration in different network environments. If a symmetric NAT is
detected, STUN will not work and ONLY an Outbound Proxy can provide a
solution.
Secondary Configures the IP address or Domain name of the Secondary Outbound Proxy,
Outbound Proxy Media Gateway, or Session Border Controller. Secondary outbound proxy will be
used when the primary outbound proxy fails.
DNS Mode Selects DNS mode to use for the client to look up server. One mode can be
chosen.
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Default is A Record.
DNS SRV Fail-over
The option will decide which IP is going to be used in sending subsequent SIP
Mode
packets (ex: Register refresh requests) after the list of IPs for SIP server host is
resolved with DNS SRV.
• Default (prefer server with lowest SRV priority):
The phone will always prefer to send SIP requests to the available server having
the lowest priority, and in case it's down it contacts the next one, but once the
server having lowest priority is UP again, the phone will switch over to this one.
• Saved one until DNS TTL (Stay on responding IP until DNS timeout):
On this mode, the phone will resolve DNS SRV records and tries to send the
request to the server having lowest priority and if it doesn't respond, it will move
on to the next IP until one of the servers responds, once this happen the phone
will keep contacting this responding IP until DNS timeout (30 minutes) before
starting over.
• Saved one until no response (Stay on responding IP until its failure):
On this mode, the phone will send SIP requests to the last responding IP, and it
doesn't failover/switchover to the next one until this responding server is down.
A Record: resolves IP Address of target according to domain name.
SRV: DNS SRV resource records indicate how to find services for various
protocols.
NAPTR/SRV: Naming Authority Pointer according to RFC 2915.
WP820 Administration Guide
Version 1.0.1.15
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