TR: [Performances using option 82] + [Issue with same transaction ID]

FAGART Thomas tfagart at
Sun Jul 16 10:08:40 UTC 2006


I don't know, if this is the correct mailing list, to ask this question could anybody tell me whether he's had such an experience ...



We're using isc-dhcp with DHCP option 82. This enables us to map a circuit-id (router subinterface) with a fixed ip for each customer.

We use the following config
class "abonne_xxx_bas-hdf64-01-4/0:551:551" {       #abonnexxx
     match if option agent.circuit-id = "bas-hdf64-01:GigabitEthernet 4/0.551:551"; }

And then

pool {
   allow members of "abonne_xxx_bas-hdf64-01-4/0:551:551";
   range a.b.c.d;
   default-lease-time 78000;
   max-lease-time 200000;

This has been working properly for more than two years now.

But now we "deliver" IPs to more than 5000 customers and our dhcpd.conf is quite heavy (about 30 000 lines of configuration)

ossau# more /usr/local/etc/dhcpd.conf | wc -l

We have the feeling that dhcpd begins to be slower when it answers to DHCP request. (Especially when it's loaded or when we reduce dhcpd lease time).

If we reduce dhcpd lease time to much, it happens that our dhcp relay and the servers can't even handle all the request properly ...

Our servers are V120 from SUN with 1Gb of RAM.

real memory  = 1073741824 (1024 MB)
avail memory = 1025818624 (978 MB)
cpu0: Sun Microsystems UltraSparc-IIe Processor (648.00 MHz CPU)

Does anybody has such a configuration or knows how we could optimize things so that our servers could be able to deal with more and more requests ?

Also unfortunately the CPEs that does the DHCP request does not follow RFCs, they always use the same transaction ID instead of choosing it randomly, (meaning that each CPE customers use Transaction ID 1234).

I'm quite sure this affects our DHCP servers especially when there are a lot of request at the same time.

Could anybody tell me whether this is "really" bad or doesn't matter ?

Thanks for your answers and sorry for this long mail.

Thomas Fagart
Responsable Exploitation
Société AXIONE 
26, Avenue des Lilas 
64062 PAU cedex 9
Tel : 05 40 03 10 42
GSM : 06 23 65 78 87
Fax : 05 59 14 86 50 
E-mail : thomas.fagart at

More information about the dhcp-users mailing list