User`s guide

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Backup IP Addresses
This page contains a table that is used to specify alternative IP addresses to use when the
router fails in an attempt to open a socket. These addresses are used only for socket
connections that originate from the router and are typically used to provide back-up for XOT
connections, TANS (TPAD answering) connections or any application in which the unit is
making outgoing socket connections.
When a backup address is in use, the original IP address that failed to open is tested at
intervals to check if it has become available again. Additionally, at the end of a session, the
unit will remember when an IP address has failed and use the backup address immediately
for future connections. When the original IP address becomes available again, the router will
automatically detect this and revert to using it.
The table has the following four column headings:
IP Address a.b.c.d
This text box should contain the original IP address to which the back-up address relates.
Backup IP address a.b.c.d
This text box should contain the backup address to try when the router fails to open a
connection to the previous IP address.
Retry Time s (seconds)
This text box contains the length of time (in seconds) that the router will wait between
checks to see if a connection can be made to IP Address.
Try Next
In the case that a connection to the primary IP address has just failed, this text box
determines whether a connection to the backup IP address should be attempted
immediately or when the application next attempts to open a connection. When checked,
the socket will attempt to connect to the backup IP address immediately after the
connection to the primary IP address failed and before reporting this failure to the calling
application, e.g. TPAD. If the backup is successful this means that the application will not
experience any kind of failure even though the router has connected to the backup IP
address.
When unchecked, the socket will report the failure to connect back to the calling application
immediately after the connection to the primary IP address has failed. The router will not try
to connect to the backup IP address at this stage. The next time that the application
attempts to connect to the same IP address, the router will instead, automatically connect
to the backup IP address.
As is usual for these tables, the Add button and Delete button are used to add and delete
entries to and from the table respectively.
Send “Backup IP” system messages to IP Address: a.b.c.d
The IP address in this text box specifies the destination to which system messages notifying
of the unavailability of an IP address should be sent. This allows the router to send UDP
messages to other routers to notify them that an IP address has become
available/unavailable. Devices that receive the IP address available/unavailable messages
Will search their own backup IP address tables for the IP addresses indicated and tag those
addresses as available/unavailable as appropriate.
Chaining IP Addresses
It is possible to chain backup IP addresses by making multiple entries in the table.
For example, if the backup IP address for the original IP address appears as the IP address
in the next row, along with a new backup IP address for that IP address, then when, the
original IP address becomes unavailable, the router will try the backup IP address and if