Enabling broadcast limit on ProCurve 5400zl series

[BOVC]

Hi,

I've worked with the 5300xl series before, and back then to enable broadcast limit, all you had to do was to well... enable it :)

Now, with these 5400zl series, it is enabled per port with a percentage specified.

Can anyone tell me what the recommended setting is? On or off - and if ON, with what percentage setting?

Thanks in advance,
Rasmus

BTW - you cannot read about this in the manual from HP. They write about it as if it is the 5300 series thay're talking about.

[Matt Hobbs · Accepted solution]

30% has been a number that has been floating around procurve land as the default broadcast limit since the 4000M days.

It really is up to you though, most networks I can never imagine seeing 30% of traffic being broadcast-traffic.

What this command does is help in the event of something sending out excessive broadcast traffic, be it from an application, a faulty NIC, or maybe a loop in the network.

Without broadcast-limit you would usually find the network to be completely unusable until you found the culprit.

Personally I don't enable it as I've found most broadcast storms are caused by loops in the network, and spanning-tree is better suited to take care of this.

Since it also affects multicast traffic, there is potential for it to slow down things like ghosting applications, or video streaming. With gigabit links this isn't so much of a concern though as there is probably more than enough bandwidth there.

Before enabling it you should take these things into consideration to see if the advantages outweigh the disavantages for your particular network.

[Marcus_20]

Matt,
I have a 5308xl that just does L2 switching. I have both igmp and broadcast-limit enabled. Do you mean this is a bad idea?

Can you ellaborate on the subject?

Best regards,
Marcus

[Matt Hobbs]

With the broadcast-limit also limiting multicast traffic, I've never tried it out myself to see exactly how it affects it. I think there is a potential for degraded performance depending on what percentage of bandwidth the multicast traffic is using.

I'm not sure what the majority of multicast traffic is on your network. If it's ghosting, then I wouldn't imagine much of a performance hit as it will always be limited by the slowest client anyway.

If you have a lot of multicast video traffic then if there was a problem, you'd already be noticing it.

Best thing to do would be to disable the broadcast-limit in your network and see if there is a performance improvement with your multicast application.