RuggedCom RuggedRouter RX1100 - Manual (Page 182)

18. Link Backup
Revision 1.14.3 182 RX1000/RX1100™
18. Link Backup
18.1. Introduction
This chapter familiarizes the user with:
• Configuring link backup
• Obtaining system status
• Testing link backup
18.1.1. Link Backup Fundamentals
Link backup provides an easily configured means of raising a backup link upon the failure of a
designated main link. The main and backup links can be Ethernet, CDMA or Dial Modem, TE1, DDS,
ADSL or T3. The only requirement is that the main link be a "permanent" link raised at boot time.
The feature can back up to multiple remote locations, managing multiple main:backup link
relationships. When the backup link is a modem, many "profiles" of dialed numbers can exist (each
serving as a distinct backup link).
The feature can back up a permanent high speed WAN link to a permanent low speed WAN link. This
is used when OSPF cannot be employed, such as on public links.
The feature can be used to migrate the default route from the main to the backup link.
The time after a main link failure to backup link startup and the time after a main link recovery to
backup link stop are configurable.
The status of the system and a method of testing fail over is provided.
18.1.1.1. Path Failure Discovery
In order to discover the failure of a primary path (here, through Network A) the link backup daemon will
both inspect the link status of the main link and send a regular ping to a designated host. In this way,
failures of network links within the cloud are discovered. It is essential that the host always respond
to the ping. Another option is to configure a dummy address within the router and ping that address.