Server Fault is a question and answer site for system and network administrators. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I has a simple freebsd 9.0 machine.But everytime i start my freebsd and use command dmesg. There aren't any hardware information there but full of

         "Limiting icmp unreach response from 1293 to 200 packets/sec"


Does any one there can tell me why this happen? And how can i erase this ?

share|improve this question
You forgot to ask a question. – David Schwartz Jun 20 '12 at 3:55
Sorry. for my poor english. – altman Jun 20 '12 at 4:02
What is the server doing? When does it happen? (All the time? Only when you run specific networking testing or analysis tools?) – David Schwartz Jun 20 '12 at 4:12
up vote 1 down vote accepted

It seems that your machine is being hit by UDP packets which are destined to closed ports. So, it is generating ICMP unreachable responses and this message tells you that the current limit 200 packets/sec has been reached. You need to find the reason of such a traffic. Packet capturing tools like tcpdump/wireshark are very useful to diagnose such problems. You can find the packets received by your machine and who is sending them.

share|improve this answer
Thank you. I will follow your thought. – altman Jun 24 '12 at 13:06

Also you can disable this messages by sysctl:

sysctl -w net.inet.tcp.blackhole=2
sysctl -w net.inet.udp.blackhole=1

More info in man blackhole

share|improve this answer

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.