DHCP out of addresses

[Guest]

My DHCP server is out of addresses. We are using a simple class C subnet and
are approaching 250 machines on the network. What I'm wondering is should we
look to start subnetting or expand our subnet mask to a /23 or so. Does
anyone have any good documentation on what we should do?

Thanks for any info!

 

[Kurt]

There's no right or wrong way, but it really depends on your infrastructure
and what services you're running, what kind of clients you have.
If you're a broadcast based NetBIOS network (No Active Directory, DNS or
WINS), you'll need to go with the wider open subnet mask. If you run WINS or
an Active Directoy with DNS and and all of your clients are capable, you can
go with additional subnet(s). If you do, you'll either need a DHCP server on
each subnet, or a DHCP relay. You'll also need a router and broadcast
isolation to make it all work properly. If you're just adding a few hosts,
the simple thing to do is open up the subnet mask, especially if you
configure with DHCP. Check your current lease time, and set it for 1 day,
then reconfigure your DHCP to issue additional addresses and the new subnet
mask. Then, over the weekend all DHCP leases will expire and everybody
should get the updated settings, after which you can extend your lease time
back to wherever it was. You'll also need to set the new subnet mask on
printers and statically configured hosts or they won't be able to talk to
addresses oustide of the scope of their subnet mask.

....kurt

 

[Phillip Windell]

Keep it simple and don't fool around with masks. Just add another /24 IP
Block and use a router between them. Ethernet begins to loose effieciency
after 250-300 hosts any so don't go make the single segment bigger than it
is. If you have that many host then they can also afford a "LAN Router", or
you can build one out of an old NT4 workstation box or Linux box. NT4
Workstation can easily operate as a simple router without needing RRAS or
the Server OS.

--
Phillip Windell [MCP, MVP, CCNA]
www.wandtv.com
-----------------------------------------------------
Understanding the ISA 2004 Access Rule Processing
http://www.isaserver.org/articles/ISA2004_AccessRules.html

Microsoft Internet Security & Acceleration Server: Guidance
http://www.microsoft.com/isaserver/techinfo/Guidance/2004.asp
http://www.microsoft.com/isaserver/techinfo/Guidance/2000.asp

Microsoft Internet Security & Acceleration Server: Partners
http://www.microsoft.com/isaserver/partners/default.asp

Deployment Guidelines for ISA Server 2004 Enterprise Edition
http://www.microsoft.com/technet/prodtechnol/isa/2004/deploy/dgisaserver.mspx