Cisco Cisco Expressway Maintenance Manual
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Small/Medium systems: 1 pair of RTP and RTCP media demultiplexing ports are used. They can either be
explicitly specified or they can be allocated from the start of the general range of traversal media ports.
explicitly specified or they can be allocated from the start of the general range of traversal media ports.
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Large systems: 6 pairs of RTP and RTCP media demultiplexing ports are used. They are always allocated from
the start of the traversal media ports range.
the start of the traversal media ports range.
Configuring Ports for Connections From Traversal Clients
Each traversal server zone specifies an H.323 port and a SIP port to use for the initial connection from the client. Each
time you configure a new traversal server zone on the Expressway-E, you are allocated default port numbers for these
connections:
time you configure a new traversal server zone on the Expressway-E, you are allocated default port numbers for these
connections:
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H.323 ports start at UDP/6001 and increment by 1 for every new traversal server zone.
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SIP ports start at TCP/7001 and increment by 1 for every new traversal server zone.
You can change these default ports if necessary but you must ensure that the ports are unique for each traversal
server zone. After the H.323 and SIP ports have been set on the Expressway-E, matching ports must be configured on
the corresponding traversal client. Note that:
server zone. After the H.323 and SIP ports have been set on the Expressway-E, matching ports must be configured on
the corresponding traversal client. Note that:
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The default port used for the initial connections from MXP endpoints is the same as that used for standard RAS
messages, that is UDP/1719. While you can change this port on the Expressway-E, most endpoints will not
support connections to ports other than UDP/1719, therefore we recommend that you leave this as the
default.
messages, that is UDP/1719. While you can change this port on the Expressway-E, most endpoints will not
support connections to ports other than UDP/1719, therefore we recommend that you leave this as the
default.
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You must allow outbound connections through your firewall to each of the unique SIP and H.323 ports that are
configured on each of the Expressway-E’s traversal server zones.
configured on each of the Expressway-E’s traversal server zones.
The following table shows the default ports used for connections to the Expressway-E.
Protocol
Call signaling
Media
Assent
TCP/2776: listening
port for H.225 and
H.245 protocols
port for H.225 and
H.245 protocols
The RTP and RTCP media demultiplexing ports in Large system are always
allocated from the start of the general range of traversal media ports
(UDP/36000-36011*). In Small/Medium systems the media demultiplexing
ports can either be explicitly specified or they can be allocated from the start
of the traversal media ports range.
allocated from the start of the general range of traversal media ports
(UDP/36000-36011*). In Small/Medium systems the media demultiplexing
ports can either be explicitly specified or they can be allocated from the start
of the traversal media ports range.
H.460.18/19 TCP/1720: listening
port for H.225
protocol
protocol
TCP/2777: listening
port for H.245
protocol
port for H.245
protocol
The RTP and RTCP media demultiplexing ports in Large systems are always
allocated from the start of the general range of traversal media ports
(UDP/36000-36011*). In Small/Medium systems the media demultiplexing
ports can either be explicitly specified or they can be allocated from the start
of the traversal media ports range.
allocated from the start of the general range of traversal media ports
(UDP/36000-36011*). In Small/Medium systems the media demultiplexing
ports can either be explicitly specified or they can be allocated from the start
of the traversal media ports range.
RTP and RTCP media non-demultiplexing ports are allocated from the
remainder of the traversal media ports range: UDP/36002-59999*.
remainder of the traversal media ports range: UDP/36002-59999*.
SIP
SIP call signaling
uses the same port as
used by the initial
connection between
the client and server.
uses the same port as
used by the initial
connection between
the client and server.
Where the traversal client is an Expressway, SIP media uses Assent to
traverse the firewall.
traverse the firewall.
Table 3 Default traversal port connections
* The default media traversal port range is 36000 to 59999, and is set on the Expressway-C at Configuration
> Traversal Subzone. In Large Expressway systems the first 12 ports in the range – 36000 to 36011 by default – are
always reserved for multiplexed traffic. The Expressway-E listens on these ports. You cannot configure a distinct
range of demultiplex listening ports on Large systems: they always use the first 6 pairs in the media port range. On
Small/Medium systems you can explicitly specify which 2 ports listen for multiplexed RTP/RTCP traffic, on the
Expressway-E (Configuration > Traversal > Ports). If you choose not to configure a particular pair of ports (Use
configured demultiplexing ports = No), then the Expressway-E will listen on the first pair of ports in the media
traversal port range (36000 and 36001 by default).
> Traversal Subzone. In Large Expressway systems the first 12 ports in the range – 36000 to 36011 by default – are
always reserved for multiplexed traffic. The Expressway-E listens on these ports. You cannot configure a distinct
range of demultiplex listening ports on Large systems: they always use the first 6 pairs in the media port range. On
Small/Medium systems you can explicitly specify which 2 ports listen for multiplexed RTP/RTCP traffic, on the
Expressway-E (Configuration > Traversal > Ports). If you choose not to configure a particular pair of ports (Use
configured demultiplexing ports = No), then the Expressway-E will listen on the first pair of ports in the media
traversal port range (36000 and 36001 by default).
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Cisco Expressway Administrator Guide
Firewall Traversal