DHCP Drops Packets

[Bjarne Blichfeldt]

Hi


> I also noticed that there was these options as well
> 
> sysctl net.ipv4.udp_wmem_min
> sysctl net.ipv4.udp_rmem_min

To be honest, I found it very hard to find exact documentation for linux tunables, but for the original issue the important
stuff is net.core.*.max values.
More info here :
http://wwwx.cs.unc.edu/~sparkst/howto/network_tuning.php

> 
> Is it worthwhile to change those, maybe instead of the TCP ones? Because the
> performance issue from Bjarne was modify tcp which is not part of DHCP correct
> (unless we're talking about fail over)?
> net.ipv4.tcp_rmem = 4096 87380 16777216
> net.ipv4.tcp_wmem = 4096 65536 16777216
> 
> Now I have to figure out how to make it permanent.

As Alex wrote, just put it into /etc/sysctl.conf:
/etc/sysctl.conf
# Network buffer settings ! Important !
net.core.rmem_max = 16777216
net.core.wmem_max = 16777216
net.ipv4.tcp_rmem = 4096 87380 16777216
net.ipv4.tcp_wmem = 4096 65536 16777216


> 
> We almost lost the service to be placed on Windows. So I'm glad we avoided
> that.
I know what you mean. When I was hit by this, I was sweating big time for a couple of days. I had replaced the windows dhcp servers
with linux/ isc-dhcp last year and I had windows people and network people all over me. Not funny.



Regards,
Bjarne