User`s manual

Supplement to DT-6061 User's Manual (Platform) for

IP -LTCN Application

04/23/02

Datatek Applications Inc.

• The other DT-6061 is already active, so this standby updates its internal time-of-day from the

active and continues to poll.

• The other DT-6061 is also in standby, so a brief negotiation follows, and one of them

becomes active, while the other remains in standby.

The standby periodically polls the active. If the active DT-6061 fails to respond to probes from the

standby (for approximately 25 seconds), the standby takes over as active by starting up the IP-

LTCN application on itself.

The active also tracks the status of the other DT-6061, and remembers the most recent poll from

the standby. If polls from the standby are overdue, the active initiates polling at a low frequency.

The physical proximity of the two DT-6061's must be near enough on the LAN to provide a

reasonably reliable connection between the two DT-6061’s. There can be intervening hubs and

ethernet switches. However, the subnetwork portion of the IP address of both DT-6061’s must be

the same. Since each DT-6061 serves as the standby machine for the other, the two DT-6061’s

should have different power sources, i.e. be on different power circuits.

If the network connection between the active and standby is broken, the network becomes

partitioned, the standby cannot receive responses from the active, and then the standby will take

over as active (at least on the portion of the network where it remains connected). When the

connection is reestablished, the two actives soon see each other (because an active initiates

polling when the standby has not been seen) and respond to this impermissible situation by

rebooting. Upon reboot, they negotiate to choose a new active and standby. Note that a reboot

takes less than 30 seconds to complete.

2.5.1 CONFIGURATION FOR HIGH AVAILABILITY

Two new configuration objects are required for the high availability option: ippublic and ipother.

Each DT-6061 has its own IP address that was configured in step 2.1 above. High availability

configuration requires choosing a third IP address, ippublic that has the same network portion of

its IP address as the two DT-6061's addresses. This public address is the one to be advertised to

all other network elements that might be configured to interoperate with this DT-6061 pair. High

availability is enabled by configuring each DT-6061 with both ipother (the ipaddr of the other DT-

6061) and ippublic. Each DT-6061 must then be rebooted to enter high availability mode.

On each DT-6061, key-in the following from the DT-6061 console:

Syntax: ippublic <ipaddress>

ipother <ipaddress>

reboot

The initial setup of a pair of DT-6061’s is now complete.

Tip: If your installation has already been running with a single DT-6061, and now a second DT-

6061 is being added to enable the high-availability option, make the ippublic address the same

as the IP address of the existing DT-6061, and give it a new IP address. This way, the IP

addresses in the DT-4000’s and DT-2020/DT-2020I

converted SAMs used by various network

elements to point at the DT-6061 will not have to be changed.

The DT-2020 and DT-2020I are two products available from Datatek Applications, Inc which permit the

conversion of an existing SAM8, SAM16, SAM64, SAM128 or SAM504 (with 128 ports or less) for use