From: John Underhill (stepnwlf@magma.ca)
Date: Sat Jun 12 2004 - 15:10:55 GMT-3
Unfortunately this doesn't scale very will on a /24 subnet.. What I mean to
do, is move away from centralized address management, and have access
routers handle dhcp for the local fabric. Right now I am using an active
cluster dhcp/dns solution, but for security reasons, (lease spoofing,
particularly for wireless, and more restrictive traffic policies at access
points..), I would like to go with a distributed solution. The only problem
is redundancy.. I was thinking of using HSRP to load share on redundant
gateways, and splitting the scope between the two dhcp servers, each
assigning different gateways.. the only problem is, there are 200+ nodes on
this segment, so if one of the DHCP servers goes down, a divided scope will
not have enough address space to service the network. So what I was thinking
was: could I log both dhcp servers to a central database on a server, let
them both use the same scope, and maintain redundancy and the full address
space, while avoiding address assignment conflicts. So the question becomes,
what does the 'ip dhcp database tftp://x.x.x.x/filename' do exactly? I am
under the impression, that it stores mappings for recovery purposes, but how
dynamic is it? Do the servers simply write to the file, or do they do a
lookup in the database before assigning an address? If it was the latter, I
could have both servers connected to the same database to avoid address
conflicts, and load share the gateways.
----- Original Message -----
From: "Kenneth Wygand" <KWygand@customonline.com>
To: <stepnwlf@magma.ca>; <ccielab@groupstudy.com>
Sent: Saturday, June 12, 2004 1:38 PM
Subject: Re: DHCP Failover
> John,
>
> Just set up two DHCP servers on the same segment but have each one lease
out a non-overlapping subset of the dynamic IP addresses in that range. This
works perfectly. If you'd like, I can explain how this actually works behind
the scenes once I get to a real computer (on a blackberry right now). Let me
know and hope this helps.
>
> Ken
> --------------------------
> Sent from my BlackBerry Wireless Handheld
>
>
> -----Original Message-----
> From: nobody@groupstudy.com <nobody@groupstudy.com>
> To: ccielab@groupstudy.com <ccielab@groupstudy.com>
> Sent: Sat Jun 12 12:52:42 2004
> Subject: DHCP Failover
>
> I was wondering if by using the (ip dhcp database tftp://x.x.x.x/filename,
> maybe in conjunction with the update arp - secure dhcp..), could I create
> overlapping scopes, and use this for redundancy? This file will store the
> binding information, but I'm wondering if the dhcp servers consult this
file
> before leasing an address, or is it simply warehousing the binding
> information.. Can someone think of some other way to create a
> redundant/failover dhcp solution using ios dhcp?
>
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