broadcast-limit not working or what do i not do right?

[franklimstrand]

Hi members

(HP E5406 zl)

This is configured on my port:

interface C23
   broadcast-limit 30
   name "bofh"
   no power-over-ethernet
   exit

So on my linux workstation i run the (slightly modified) 'udp1' from the libnet (c library) package:
./udp1 -s 1.1.1.1.666 -d 255.255.255.255.1 -n 9999999999 -p thisismypayload

So with 'tcpdump' i see:

15:25:47.093263 18:03:73:e8:3a:d4 > ff:ff:ff:ff:ff:ff, ethertype IPv4 (0x0800), length 1510: (tos 0x0, ttl 64, id 242, offset 0, flags [none], proto UDP (17), length 1496, options (NOP,EOL))
    1.1.1.1.666 > 255.255.255.255.667: [udp sum ok] UDP, length 1448

This is an example of broadcast traffic right? With this pattern i can easily saturate my 1Gbps network link and a short test of this is "felt" in the network. I thought this should be limited so what do i not get?

With regards
Frank

[Richard Brodie_1]

Pick one of:

1. It's a percentage of the nominal bandwidth, so still a lot.
2. Is for outbound traffic on the specified port.

[franklimstrand]

Hi Richard

Thank you for answering.

This is outbound traffic (from my linux pc) and we have just tried lowering the broadcast-limit to 5% and then 1% but still i can easily saturate my 1Gb link with broadcast traffic. I am doing 3-4 seconds tests at the time as the broadcast traffic is causing trouble for some services in the network.

/FrankL

[Richard Brodie_1 · Accepted solution]

Outbound traffic from the POV of the switch, that is. If your PC is on port C23, then it won't filter it; you would need to apply the rule to all the other ports.

[franklimstrand]

Hi Richard

Yeah, you are right (just tested) - thank you. Not quite what we expected but now we know what we are up against.

/FrankL