Advanced Network Settings descriptions
Digi TransPort User Guide
497
Backup IP addresses
This page contains a table that is used to specify alternative IP addresses to use when the router
fails when attempting 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 router 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 router
remembers when an IP address has failed, and uses the backup address immediately for future
connections. When the original IP address becomes available again, the router automatically
detects this, and reverts to using that IP address.
The table has the following four column headings:
IP Address a.b.c.d
The original IP address to which the back-up address relates.
Backup IP address a.b.c.d
The backup address to try when the router fails to open a connection to the previous IP
address.
Retry Time s (seconds)
The length of time, in seconds, the router waits between checks to see if a connection can be
made to IP Address.
Try Next
When 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 attempts 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, such as TPAD. If the backup is
successful, the application will not experience any kind of failure, even though the router has
connected to the backup IP address. When unchecked, the socket reports the failure to
connect back to the calling application immediately after the connection to the primary IP
address has failed. The router does 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
instead automatically connects to the backup IP address. Use the
Add
and
Delete
buttons to
add and delete entries to and from the table.
Send “Backup IP” system messages to IP Address: a.b.c.d
The destination IP address 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 search their own backup IP address tables for the IP
addresses indicated, and tag those addresses as available/unavailable as appropriate.
