ISC-dhcp subnet limit?

José Queiroz zekkerj at gmail.com
Thu Jan 28 16:27:38 UTC 2016


2016-01-27 23:12 GMT-02:00 Rob Morin <rmorin at datavalet.com>:

> 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?
>

Hi Rob, I saw from other messages that you're using bonded interfaces. I
understand that, as far as you start using bonded interfaces, you must
attach your DHCP server to the logical interfaces (bond0, bond1, etc), not
the physical ones. When you do that, the system will direct the packets to
one of the physical interfaces in a suitable way.

You've also said on other messages that you have two VLANs, and I
understand that your servers are capable of sending do1q labeled frames. If
so, you must have at least two logical interfaces ontop your bonded
interface; if so, you must attach your DHCP server to the vlan interfaces
(vlan1, vlan2, etc.). Keep in mind, also, that your L3 Switch (or whatever
equipment is doing your inter-vlan routing) may act as a "dhcp relay", so
you don't need that your DHCP server talks to all of the vlans, as far as
it haves connectivity with the dhcp relay.


>
> 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;
>
> }
>
>
Could you please show the configuration of your secondary DHCP server? Just
the "failover peer section" may be enough.
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