ISC-dhcp subnet limit?
Rob Morin
rmorin at datavalet.com
Fri Jan 29 15:58:10 UTC 2016
Hey Denis, thanks for the response...
I was just using apt to install isc-dchp server on ubuntu 14.04
Server is quad core xeon with 8 gigs of ram with a software raid 1 disks
But maybe i should consider your way...
I was just doing some testing using a ramdisk for the
/var/lib/dhcp/dchpd.leases files
Our leases are short for special reasons... 20 minutes
so on a dev machine i created a ramdisk of 2 gigs, and backup the leases
files to a hard disk each 5 mins, and on restart the
/etc/init/isc-dhcp-server.conf will copy the files from backup to
/ramdisk then start dhcp
on dev it works fine... but i may consider your way now...
we tend to shy away from compiling stuff.. :(
Even after 24 hours after start of the peer never came out of recovery
mode, not sure why..
Currently we made dhcp-2 a standalone server and it currently has 217335
leases in it, but i will need to double that at least in coming weeks..
Server is currently ....
top - 10:55:08 up 22:55, 2 users, load average: 2.00, 1.99, 1.93
Tasks: 116 total, 1 running, 115 sleeping, 0 stopped, 0 zombie
%Cpu0 : 0.9 us, 0.5 sy, 0.0 ni, 25.8 id, 72.8 wa, 0.0 hi, 0.0 si,
0.0 st
%Cpu1 : 1.4 us, 0.5 sy, 0.0 ni, 74.3 id, 23.4 wa, 0.0 hi, 0.5 si,
0.0 st
%Cpu2 : 0.0 us, 0.0 sy, 0.0 ni,100.0 id, 0.0 wa, 0.0 hi, 0.0 si,
0.0 st
%Cpu3 : 0.5 us, 0.0 sy, 0.0 ni, 99.5 id, 0.0 wa, 0.0 hi, 0.0 si,
0.0 st
KiB Mem: 8092320 total, 5007076 used, 3085244 free, 164496 buffers
KiB Swap: 7810044 total, 0 used, 7810044 free. 4129916 cached Mem
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+
COMMAND
12979 root 20 0 565060 559220 2524 D 2.3 6.9 15:08.17 dhcpd
1713 syslog 20 0 255848 2924 2428 S 0.9 0.0 3:16.05
rsyslogd
215 root 20 0 0 0 0 S 0.5 0.0 2:00.89
jbd2/md2-8
412 root 0 -20 0 0 0 S 0.5 0.0 1:13.95
kworker/0:1H
14300 root 20 0 0 0 0 S 0.5 0.0 0:41.33
kworker/0:2
1 root 20 0 33620 4284 2824 S 0.0 0.1 0:01.19 init
I will try your suggestion on dev machine
Do you use or know of a tool that i can use to simulate dhcp request for
testing on my dev machine?
Thanks for your help!
Rob Morin
Montreal, Canada
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On 2016-01-29 9:58 AM, Denis Laventure wrote:
>
> Hi Rob,
>
> I can't help for issue on your interface problem but I think I can
> help with the performance.
>
> I used to have performance problem with my failover setup and someone
> at ISC told me to change some value in the code to get debug
> information about memory usage.
>
> Add this to the file "includes/dhcpd.h"
>
> #if !defined (REPORT_HASH_PERFORMANCE)
>
> # define REPORT_HASH_PERFORMANCE 1
>
> #endif
>
> Compile and start the daemon and you should get something like this on
> screen and in the log:
>
> dhcpd: DHCP name hash: Contents/Size (%): 106/401 (26%). Min/max: 0/2
>
> dhcpd: DHCP code hash: Contents/Size (%): 106/254 (41%). Min/max: 0/1
>
> dhcpd: NWIP name hash: Contents/Size (%): 11/17 (64%). Min/max: 0/2
>
> dhcpd: NWIP code hash: Contents/Size (%): 11/17 (64%). Min/max: 0/1
>
> dhcpd: FQDN name hash: Contents/Size (%): 8/13 (61%). Min/max: 0/2
>
> dhcpd: FQDN code hash: Contents/Size (%): 8/13 (61%). Min/max: 0/1
>
> dhcpd: VIVCO name hash: Contents/Size (%): 1/127 (0%). Min/max: 0/1
>
> dhcpd: VIVCO code hash: Contents/Size (%): 1/127 (0%). Min/max: 0/1
>
> dhcpd: VIVSO name hash: Contents/Size (%): 1/127 (0%). Min/max: 0/1
>
> dhcpd: VIVSO code hash: Contents/Size (%): 1/127 (0%). Min/max: 0/1
>
> dhcpd: ISC name hash: Contents/Size (%): 2/3 (66%). Min/max: 0/1
>
> dhcpd: ISC code hash: Contents/Size (%): 2/3 (66%). Min/max: 0/1
>
> dhcpd: Relay Agent name hash: Contents/Size (%): 5/11 (45%). Min/max: 0/1
>
> dhcpd: Relay Agent code hash: Contents/Size (%): 5/11 (45%). Min/max: 0/1
>
> dhcpd: Server-Config Option name hash: Contents/Size (%): 67/136
> (49%). Min/max: 0/4
>
> dhcpd: Server-Config Option code hash: Contents/Size (%): 67/136
> (49%). Min/max: 0/1
>
> dhcpd: data: hardware: no raw packet or lease is available
>
> dhcpd: data: hardware: no raw packet or lease is available
>
> dhcpd: data: hardware: no raw packet or lease is available
>
> dhcpd: data: hardware: no raw packet or lease is available
>
> dhcpd: data: hardware: no raw packet or lease is available
>
> dhcpd: data: hardware: no raw packet or lease is available
>
> dhcpd: Config file: /dhcpd/dhcpd.conf
>
> dhcpd: Database file: /dhcpd/dhcpd.leases
>
> dhcpd: PID file: /var/run/dhcpd.pid
>
> dhcpd: Wrote 0 class decls to leases file.
>
> dhcpd: Wrote 0 deleted host decls to leases file.
>
> dhcpd: Wrote 0 new dynamic host decls to leases file.
>
> dhcpd: Wrote 48578 leases to leases file.
>
> dhcpd: Host HW hash: Contents/Size (%): 1420/22501 (6%). Min/max: 0/4
>
> dhcpd: Host UID hash: No table.
>
> dhcpd: Lease IP hash: Contents/Size (%): 70324/100003 (70%). Min/max: 0/5
>
> dhcpd: Lease UID hash: Contents/Size (%): 8708/100003 (8%). Min/max: 0/3
>
> dhcpd: Lease HW hash: Contents/Size (%): 9036/100003 (9%). Min/max: 0/3
>
> "Lease IP hash" is where you should look.
>
> By default the server use a lease hash size value of 100003. I had
> over 350000 leases so I was exceeding that value and the server was
> very slow to start.
>
> To change the size you must edit the file "includes/dhcpd.h" and find
> LEASE_HASH_SIZE and replace the value. This value must be a prime
> number (I used 400009).
>
> -# define LEASE_HASH_SIZE 100003
>
> +# define LEASE_HASH_SIZE 400009
>
> Compile and start again. That was the answer for me.
>
> One other thing with the failover setup, the peer will always be in
> recover state when starting for the duration of the "MCLT" (time in
> second) in your failover definition (1800 in your case), so it will be
> in recover start for 30 minutes. I use 300 (5 minutes).
>
> Le texte aurait été plus facile à écrire en français mais comme la
> liste est en anglais et que ça peut aider d'autres personnes alors je
> me suis forcé. En espérant que ce soit clair pour toi !
>
> Denis Laventure
>
> Université du Québec à Chicoutimi
>
> *De :*dhcp-users-bounces at lists.isc.org
> [mailto:dhcp-users-bounces at lists.isc.org] *De la part de* Rob Morin
> *Envoyé :* 27 janvier 2016 20:12
> *À :* dhcp-users at lists.isc.org
> *Objet :* ISC-dhcp subnet limit?
>
> Hello all, my first post here, so please be gentle J
>
> I have inherited 2 dhcp servers, one primary(dhcp-1) & one
> secondary(dhcp-2) running isc-dhcpd-4.2.4 on Ubuntu 14.0(Trusty)
>
> We are having a few issues, and I cannot seem to figure out whats
> going on. I have a few questions, maybe someone can help me with.
>
> Is there a max limit to how many subnets can be used in the pools? As
> currently we are using just over 6000 subnets
>
> Currently our secondary dhcp-server is always in recovery mode, not
> sure why?
>
> Does it matter if a DISCOVER comes in on eth1 but OFFER goes out on eth0?
>
> My primary server /etc/dhcpd.conf file
>
> authoritative;
>
> log-facility local7;
>
> option domain-name "dyn";
>
> option domain-name-servers 172.30.64.210, 172.30.64.220;
>
> default-lease-time 1200;
>
> max-lease-time 3600; # 1h
>
> include "/etc/dhcp/dhcpd_pools.conf";
>
> # Include the primary configuration
>
> include "/etc/dhcp/dhcpd_primary.conf";
>
> /etc/dhcp/dhcpd_primary has the following
>
> ## PRIMARY
>
> failover peer "tdl-dhcp-failover" {
>
> primary; # declare this to be the primary server
>
> address 172.30.128.9;
>
> port 647;
>
> peer address 172.30.128.10;
>
> peer port 647;
>
> max-response-delay 30;
>
> max-unacked-updates 10;
>
> load balance max seconds 3;
>
> mclt 1800;
>
> split 128;
>
> }
>
> Exert from dhcpd_pools file, starts like this….
>
> subnet 10.32.0.0 netmask 255.255.255.0 {
>
> option routers 10.32.0.1;
>
> pool {
>
> failover peer "dhcp-failover";
>
> range 10.32.0.5 10.32.0.254;
>
> }
>
> }
>
> And finishes like this, with all the subnets in between…
>
> subnet 10.57.255.0 netmask 255.255.255.0 {
>
> option routers 10.57.255.1;
>
> pool {
>
> failover peer "dhcp-failover";
>
> range 10.57.255.5 10.57.255.254;
>
> }
>
> }
>
> Example Exert from logs on both serves of a client that could not get
> an IP
>
>
> from dhcp-1
> Jan 27 18:30:31 dhcp-1 dhcpd: DHCPDISCOVER from fc:e9:98:bc:a8:7b
> (iPhone) via 10.50.170.1
> Jan 27 18:30:31 dhcp-1 dhcpd: DHCPOFFER on 10.50.170.93 to
> fc:e9:98:bc:a8:7b (iPhone) via 10.50.170.1
>
> from dhcp-2
> Jan 27 18:53:55 dhcp-2 dhcpd: DHCPDISCOVER from fc:e9:98:bc:a8:7b via
> 10.50.170.1: peer holds all free leases
> Jan 27 18:54:04 dhcp-2 dhcpd: DHCPDISCOVER from fc:e9:98:bc:a8:7b via
> 10.50.170.1: peer holds all free leases
>
> Never see the ACK.
>
> Any suggestion would be greatly appreciated.. :
>
> Thanks…
>
> Rob
>
> Montreal Canada
>
>
>
> _______________________________________________
> dhcp-users mailing list
> dhcp-users at lists.isc.org
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