Increasing Broadcast Message size

[Cathy Squires]

Hello,

I have a K420 server running HPUX 10.20. (No cracks please, I know it's ancient. ;) Currently the broadcast messages that are being sent out are approx 1232K, but the max size configured on the K420 is 1024K so the messages are getting split in 2 and bogging down the network with excess broadcasts.

I'm pretty sure there is a way to increase the max size of the broadcast messages, but as of yet, have not found where to make the change. I would really appreciate any help available in increasing the message size.

tks in advance
Cathy Squires

[Steven E. Protter]

If the ndd utility exists on 10.20 thats the tool you may want to use for changing this.

You'll have to do a man page or further research, because I don't know which parameter it is.

SEP

[Dave Olker]

Hi,

ndd doesn't exist on 10.20. On 10.20 the "equivalent" tool is nettune. I checked the available parameters with nettune and didn't see anything that would likely affect broadcast packet size.

Just to be sure, what MTU size is configured for the interface sending these broadcast packets? (check with lanadmin -m ) If the MTU size of the interface then it would explain the broadcast behavior you're seeing. In that case, changing the MTU size of the interface might make the difference. Just a thought...

Dave

[Dave Olker]

Sorry, meant to say - if the MTU size of the interface is set to 1024, then it would explain the broadcast behavior.

Dave

[Cathy Squires]

Hello,

Thanks for the info, but the MTU size = 1500. Anyplace else I can check? I'm looking on this end, but info on 10.20 is getting really scarce.

ecs

[Brian Hackley]

Cathy,

Just a little curious:

Are these Ethernet broadcasts, or are they IP broadcasts?

You also said 1232K/1024K ? Do you mean 1232 bytes or 1232 Kilobytes?

Here some possible help from nettune:
ip_forward_directed_broadcasts:

If ip_forward_directed_broadcasts is 0, we will check if the destination address in the packet matches with any of the broadcast addresses of all interfaces in the system and inhibits any forwarding.
If ip_forward_directed_broadcasts is 1, and the destination address of the packet does not match the addresses of the interface that it comes in, the packet will be passed to ip_forward().


Default Values:
This value can only be turned on or off.
ON:1
OFF: 0
Default: 1

Usable Commands:
Get the actual value of this tunable:

nettune -l ip_forward_directed_broadcasts

Turn of the forwarding:

nettune -s ip_forward_directed_broadcasts 0

---------------------
ip_forwarding:

This tunable controls the way a hosts forwards packets.
If someone sends a packet to this host he tries to figure out if it is possible for him to put it out on another interface to bring the packet nearer to it's destination.
This is done due to the routing information that exist on the host.
In most cases if two interfaces are configured for a host, these two interfaces are connected to different subnets.
So IP-forwarding makes sense here, because packets were sent to this host to get delivered into another subnet.

Default Values:
This value could only be turned on or off.
ON: 1
OFF: 0
Default: 1 (ON)

Usable Commands:
Get the actual setting for ip_forwarding:

nettune -l ip_forwarding
Turn off the ip_forwarding:

nettune -s ip_forwarding 0
-------------------------

Hope that helps, Brian Hackley