Version 6.6 279 October 2014
Installation & Operation Manual 31. Configuring the MGCP/MEGACO Protocols
31.4 Media Gateway Controller Addressing
There are two alternative methodologies for addressing the MGC:
via FQDN name
via IP addresses
31.4.1 Via FQDN Name
When the MGC is addressed via FQDN name, the FQDN is resolved to the IP
address through the DNS server. The DNS server can return a single IP address or a
list of up to 10 IP addresses.
The Media Gateway boards' restart procedure is complete only when the DNS server
responds to a DNS query successfully. If a DNS resolution fails, the Media Gateway
board keeps trying to resolve the FQDN name until the resolution succeeds and a
valid set of IP addresses is received. The first IP address returned by DNS is
considered to be a Primary Call Agent IP address.
Redundant DNS servers may be configured as an alternative means of FQDN name
resolution.
31.4.2 Via IP Addresses
If the MGC is to be addressed via IP addresses, you must provision a fixed list of IP
addresses. Up to 10 IP addresses may be defined. The priority of the IP addresses is
specified via the Activity Order parameter – the lower the value, the higher the
priority. The IP address with the highest priority (lowest Activity number) is considered
to be the Primary Call Agent IP and the rest of the addresses are considered to be
Redundant Call Agent IPs.
The Media Gateway board always sends its events/alarms to the Primary Call Agent
IP, unless a protocol-specific mechanism is used to modify this default behavior (e.g.,
Notified Entity element in MGCP messages).
If the Primary Call Agent IP address stops responding, the Media Gateway board's
retransmission mechanism sends commands to the 1
st
Redundant Call Agent IP,
then to the 2
nd
Redundant Call Agent IP, etc.
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