Multi-subnet/vlan and failover
Gregory Sloop
gregs at sloop.net
Fri May 10 00:08:42 UTC 2013
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
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