DHCP Drops Packets

Nathan McDavit-Van Fleet nmcdavit at alcor.concordia.ca
Fri Nov 12 18:15:32 UTC 2010


FYI I tried it without changing the [rw]tcp fields and just the other ones
and it works perfectly without errors. 

I also ended up getting some big errors with the server itself with a
"Neighbour table overflow". I wasn't sure what was going on but I was able
to at least resolve it so far with this:

http://nice3z.myfinejob.com/node/3

I'm thinking it's either because there is so much traffic to the server now
that the arp tables are getting really full (lots of subnets being spanned
via ip-helper) OR because I had put a host entry in my /etc/hosts of
"255.255.255.255 dhcp". I added that because an online guide had recommended
it fod DHCPd setup while I was trying to fix the caching issue. 

Nathan Van Fleet


> -----Original Message-----
> From: dhcp-users-bounces+nmcdavit=alcor.concordia.ca at lists.isc.org
> [mailto:dhcp-users-bounces+nmcdavit=alcor.concordia.ca at lists.isc.org]
> On Behalf Of Alan Buxey
> Sent: Friday, November 12, 2010 10:33 AM
> To: Users of ISC DHCP
> Subject: Re: DHCP Drops Packets
> 
> Hi,
> 
> > sysctl net.ipv4.udp_wmem_min
> > sysctl net.ipv4.udp_rmem_min
> >
> > 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.
> 
> 2 ways. the common way is to integrate them with sysctl - eg place them
> in the /etc/sysctl.conf
> file - it will then be pulled in at start-time.
> 
> alternatively, add commands to rc.local
> 
> > We almost lost the service to be placed on Windows. So I'm glad we
> avoided that.
> 
> ouch. thats a nasty knee-jerk reaction. ISC DHCPD on Linux is soo much
> better than
> any windows thing.  theres a reason why all appliance solutions use ISC
> DHCPD and Linux.
> 
> (higher performance etc can be with ISC DHCPD on a BSD platform.... but
> for some, the BSD
> learning experience is steep and harsh)
> 
> alan
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> dhcp-users at lists.isc.org
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