3Com Version 4.3 Chapter 12. Failover

Chapter 12. Failover

The3Com VCX IP Telecommuting Module failover function makes it possible to have a hot standby unit which

alwayshas the current conﬁguration and which automatically takes over when the active unit goes down. The two

unitsbecome a failover team.

Thisfunction requires that one interface on the Telecommuting Module is dedicated for failover and can’t be used

foranything else.

Note:This means that failover can only be used when the Telecommuting Module is used in DMZ mode.

Thisis a short description of what 3Com Failover can do and what is required to make it work.

Failoverrequires two Telecommuting Modules„ and both units must run the same software version. Any expansion

moduleson the active unit must also be present on the standby.

Theunits must be located in a way which makes it possible to connect them with a cross-over network cable. You

mustalso connect the other interface on the standby unit to the same router/switch as the active Telecommuting

Module.

TheFailover function allows you to create failover teams out of two Telecommuting Modules, where one unit is

activeand the other a standby unit. The standby stays in constant contact with the active unit to check if it’s working

andto ask for new conﬁguration whenever the conﬁguration is changed on the active Telecommuting Module.

Whenthe active unit fails, the standby takes over, with the same conﬁguration (including IP addresses).

Ifeither of the units stops working, or if the active unit can’t connect to the standby unit via the cross-over cable,

theTelecommuting Module won’t accept new changes to the conﬁguration. This is because there is no way for the

activeTelecommuting Module to transfer the changes to the standby unit. If this should happen, and there is no way

toreestablish the connection between the two units, the active unit must change mode to a standalone unit (which

breaksthe failover team) to allow changes in the conﬁguration.

Updateinterval 30s

Maximumfailover time 30s + time to apply conﬁguration

TCP/UDPconnections (session management) kept after

failover No

TCP/UDPconnections (packet ﬁlter) kept after failover Yes

SIPregistrations kept after failover Yes

SIPcalls kept after failover No

Forthe failover function to work properly, you must conﬁgure the Telecommuting Modules in the right way,and

connectthem correctly. Here is a short guide on how to do this.

Tocreate a new failover team, you must initiate the two Telecommuting Modules in differentways. The ﬁrst

TelecommutingModule is made a member of the team by web interface conﬁguration, the second is added to the

teamby means of connecting to it via the serial cable or console.

Thefollowing procedure will produce a correctly conﬁgured Telecommuting Module 1 team member:

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