ISC-dhcp subnet limit?
Rob Morin
rmorin at datavalet.com
Thu Feb 4 18:43:53 UTC 2016
Would a too low lease_hash prevent users from getting a lease or IP at a
certain point? I had this issue last night where i was running on stock
apt-get install and after we moved one more controller to that server ,
people started not being able to get leases....
With the increase of lease_has after a restart i get this
Feb 4 13:41:49 localhost dhcpd: Lease IP hash: Contents/Size (%):
1664250/400009 (416%). Min/max: 3/5
Feb 4 13:41:49 localhost dhcpd: Lease UID hash: Contents/Size (%):
0/400009 (0%). Min/max: 0/0
Feb 4 13:41:49 localhost dhcpd: Lease HW hash: Contents/Size (%):
0/400009 (0%). Min/max: 0/0
Feb 4 13:41:49 localhost dhcpd: Server starting service.
So i should up it until i have space??
Rob Morin
Gestionnaire des systèmes | Senior Systems Administrator
Tel: 514 385-4448 #174
DATAVALET.COM
5275, chemin Queen-Mary, Montréal (Québec) H3W 1Y3 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
>
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