Multi-subnet/vlan and failover

[Gregory Sloop]

So, I've done a fair bit of reading and searching - and this general
template is what I thought would work, but it doesn't.

Let me post the dhcp.conf file and then discuss what's wrong and ask
for pointers.

---
authoritative;
#ddns-update-style interim;
ignore client-updates;
#option host-name = config-option server.ddns-hostname;

#include "/etc/rndc.key";

option domain-name              "somedom.local";
option domain-name-servers      10.1.1.190,10.1.2.1,10.1.1.17;
option time-offset              -18000; # Pacific Standard Time
option ntp-servers              10.1.1.14
one-lease-per-client off;

#4 hour lease
default-lease-time 14400;
max-lease-time 14400;
option ip-forwarding off;

failover peer "dhcp-failover" {
  primary; # declare this to be the primary server
  # Address if THIS dhcp server, or what address to listen ON
  address 10.1.1.1;
  port 647;
  # Address of the DHCP fail-over peer.
  peer address 10.1.1.2;
  peer port 647;
  max-response-delay 60;
  max-unacked-updates 10;
  #load balance max seconds 3;
  mclt 3600;
  split 0;
}

    subnet 10.1.1.0 netmask 255.255.255.0 {
        range 10.1.1.1 10.1.1.254;
        option routers                  10.1.1.1;
        option subnet-mask              255.255.255.0;
        failover peer "dhcp-failover";
    }

    subnet 10.1.2.0 netmask 255.255.255.0 {
        range 10.1.2.1 10.1.2.254;
        option routers                  10.1.2.1;
        option subnet-mask              255.255.255.0;
        failover peer "dhcp-failover";
    }

    subnet 10.1.3.0 netmask 255.255.255.0 {
        range 10.1.3.1 10.1.3.254;
        option routers                  10.1.3.1;
        option subnet-mask              255.255.255.0;
        failover peer "dhcp-failover";
    }

---
Now, I've disabled DDNS updates for simplicity sake. Once I get the
multi-subnet/VLAN setup and failover working I'll add that back.

Perhaps that impacts things somehow, so if you'll keep that in mind,
I'd appreciate it.

So, when I try this config I get an error saying that a failover needs
to be inside a shared network block.

But if I do that, I've been told [read] that the DHCP server won't
know how to assign the different subnets. [This would apply to a
network where I wanted to share all the 10.1.1.1-10.1.3.254 as a
single pool/block and assign any station any IP in the whole block.]

But I have a L3 switch and I want these assigned to each VLAN.

---
So, I setup the conf file without a shared-network and it works fine
with the L3 DHCP helper/proxy. Clients on VLAN1 get 10.1.1.0 blocks
and VLAN2 get 10.1.2.0 blocks etc.

So, with the "failover" block commented out, it works charmingly! Very
cool!

---
But I *also* want to use failover.

And when I put in a fail-over outside a shared-network, it complains
that it must be inside a shared network.

So, how to I use fail-over AND maintain the subnet grouping above?

---
I'll keep reading, but I've tinkered with this quite a bit and for the
life of me, I can't see how one would go about it.

-Greg




-- 
Gregory Sloop, Principal: Sloop Network & Computer Consulting
503.251.0452 x121 Voice | 503.251.0452 Fax
www.sloop.net
mailto:gregs at sloop.net