ISC-dhcp subnet limit?
Rob Morin
rmorin at datavalet.com
Thu Jan 28 02:21:48 UTC 2016
Fyi, each server is a quad core xeon with 8 gigs of ram, one server will have its disk replaced as its not a raid and it has a high wait time of 95% all the time, secondary server has a raid1 same specs as first server and wait time is under 5% most of the time.
Both servers have bonded(lacp) nics so total bandwidth is 2 gigs(2x1gig ports)
Rob Morin
Gestionnaire des systèmes | Senior System administrator
T 514 385-4448 #174 DATAVALET.COM
5275, chemin Queen-Mary, Montréal (Québec) H3W 1Y3 Canada
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-----Original Message-----
From: dhcp-users-bounces at lists.isc.org [mailto:dhcp-users-bounces at lists.isc.org] On Behalf Of Rob Morin
Sent: Wednesday, January 27, 2016 9:18 PM
To: Users of ISC DHCP <dhcp-users at lists.isc.org>
Subject: RE: ISC-dhcp subnet limit?
Thanks for the quick reply Dave, on each of the servers there are 2 vlans, one is internal/admin(VLAN01) and one is dmz(VLAN02), where the requests/discovers come in. From my testing so far it seems that a discover comes in on vlan02, and the offer and ack go out on vlan01. I do not think this is an issue as per our network guys, but I thought I would mention it.
Discover comes in via vlan02 through a firewall, but when it goes out on vlan01 there is no firewall.
Here is /etc/dhcp/dhcpd.conf of secondary
authoritative;
log-facility local7;
option domain-name "dyn";
default-lease-time 1200; # 20 minutes to match the default clients session duration max-lease-time 3600; # 1h include "/etc/dhcp/dhcpd_secondary.conf"; include "/etc/dhcp/dhcpd_pools.conf";
Here is the "/etc/dhcp/dhcpd_secondary.conf file
## SECONDARY
failover peer "dhcp-failover" {
secondary; # declare this to be the secondary server address 172.30.128.10; port 647; peer address 172.30.128.9; peer port 647; max-response-delay 30; max-unacked-updates 10; load balance max seconds 3; # mclt 1800; #No "split" statement on secondary }
Our lease time is short as per client request, we cannot alter it, its in the contract.
As for users, there are 10's of thousands of users at any given time...
Here is a very recent log exert on secondary..
Jan 27 21:10:29 dhcp-2 dhcpd: DHCPDISCOVER from 68:d9:3c:56:a6:bb via 10.49.66.1: not responding (recovering) Jan 27 21:10:29 dhcp-2 dhcpd: DHCPDISCOVER from 10:a5:d0:17:34:96 via 10.37.5.1: peer holds all free leases Jan 27 21:10:29 dhcp-2 dhcpd: DHCPREQUEST for 10.37.104.252 (172.30.129.9) from 5c:8d:4e:a2:06:ff via 10.37.104.1: not responding (recovering) Jan 27 21:10:29 dhcp-2 dhcpd: DHCPREQUEST for 10.50.33.204 (172.30.129.9) from 90:e7:c4:d3:7d:51 via 10.50.33.1: not responding (recovering)
Here are some misc log entries that you might find useful...
Jan 27 14:45:03 dhcp-1 dhcpd: Wrote 1169142 leases to leases file.
Jan 27 15:29:21 dhcp-1 dhcpd: Wrote 1169401 leases to leases file.
Jan 27 16:17:35 dhcp-1 dhcpd: Wrote 1169721 leases to leases file.
Jan 27 15:50:25 dhcp-1 dhcpd: peer dhcp-failover: disconnected Jan 27 16:19:38 dhcp-1 dhcpd: peer dhcp-failover: disconnected
Jan 27 16:16:39 dhcp-2 dhcpd: peer dhcp-failover: disconnected Jan 27 16:18:55 dhcp-2 dhcpd: peer dhcp-failover: disconnected Jan 27 14:15:51 dhcp-2 dhcpd: Wrote 0 leases to leases file.
Jan 27 15:28:38 dhcp-2 dhcpd: Wrote 29890 leases to leases file.
Jan 27 15:35:41 dhcp-2 dhcpd: Wrote 29920 leases to leases file.
Jan 27 15:50:28 dhcp-2 dhcpd: Wrote 29920 leases to leases file.
Any help appreciated...
Rob
Montreal, Canada
-----Original Message-----
From: dhcp-users-bounces at lists.isc.org [mailto:dhcp-users-bounces at lists.isc.org] On Behalf Of dave c
Sent: Wednesday, January 27, 2016 9:02 PM
To: Users of ISC DHCP <dhcp-users at lists.isc.org>
Subject: Re: ISC-dhcp subnet limit?
Curious why your network seems to have 6,000 subnets all living in a single vlan...
But, in order to diagnose the partner issue, we'd need to see the partner config segments as well.
To answer whether it matters if requests arrive on eth1 and answers go out on eth0, the real question is what are the differences between them. Does one go out to a firewall while the second is a direct connection? I don't see a statement in your config telling dhcpd which IP address/port to listen and respond on. You can force it to use eth1 if you feel it should be doing so.
I'm also wondering why your lease time is so short. That would seem to generate a lot of traffic to the dhcp server that otherwise wouldn't be needed. How many users are there in these 6,000 subnets?
Dave
On 1/27/16 19:12, Rob Morin wrote:
> 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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> dhcp-users at lists.isc.org
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>
--
Dave Calafrancesco
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