System information

AS/400 IBM Network Station: Techniques for Deployment in a WAN

1.2.4 Broadcast Boot for AS/400

The broadcast boot support in IBM Network Station Manager for AS/400

Release 3 provides the capability to boot multiple Network Stations on the

same subnet. This broadcast boot is performed in parallel through a single

transmission. In situations where large numbers of IBM Network Stations

start up at the same time, heavy network usage or boot storms can result.

Trivial File Transfer Protocol (TFTP) Subnet Broadcast (or Broadcast Boot) is

a solution to balancing your network traffic during these boot storms because

it reduces LAN usage and AS/400 CPU utilization.

The reason boot storms may occur is that the AS/400 server is trying to

deliver the boot kernal file to every IBM Network Station in the network. When

the TFTP Subnet Broadcast option is enabled and multiple IBM Network

Stations request their boot files, the server stages the boot file download and

only distributes it

once

. Essentially, the first Network Station on the subnet

which requests its boot file becomes the

master

. When other IBM Network

Stations on the same subnet request their boot files, the

master

serves them.

It passes on the files received during its initialization. The

master

continues

its role until it has completed its initialization. Once completed, the

master

role passes to the next IBM Network Station that requests the kernal file. This

sequence continues until new IBM Network Station assumes the role of

master

You must enable the TFTP Subnet Broadcast option on both the AS/400

server and the IBM Network Station. By default, the TFTP Subnet Broadcast

option is enabled on your AS/400. However, as shown in Figure 3 on page 11,

you should verify this by typing in

CHGTFTPA and ensure that the

Enable Subnet

Broadcast

parameter value is set to *YES. You must then start up the Network

Station Manager from your browser, and as shown in Figure 4 on page 11,

select the Hardware/Workstation Setup Task to change the

Enable Broadcast

Boot

Ye s.