DHCP on a windows server or switch

[steyler]

I have this on going disagreement with our Windows admin about DHCP. My preference is run DHCP on the switches but he says it's a function of a Windows server. I'm trying to make an argument to take over dhcp but have only come with "it will save spare the network of broadcasts". Also that it relates to IP addressing. Does anyone have an opinion on which is the better way? Windows server or switch? Thanks.

 

[vipergg]

Hate to go against you but it most instances servers at least in a bigger enviroment is the way most people go . Its less of a load on the switches and I think you have more config options on a server , maybe someone else can chime in as I don't do a lot of work on dhcp servers . It justs seems it would be a pain to put them on switches , you would have to set it up on multiple switches and try to keep everything synchronized , just seems like more problems than it is worth where as servers are really setup to do this . I think dhcp on cisco gear is really setup for small setups maybe a few vlans in a office where they don't want to invest in servers .

 

[ADB100]

I have to agree with vipergg on this as well. DHCP (on Windows servers) offers more flexibility than doing this on IOS platforms. One thing that is becoming more common now is Vendor Class Identification which is only really supported on Windows. VCI's are great if you have overlapping Vendor Options - Vendor Option 43. Most DHCP Clients now indicate what they are through Option 60, this allows your DHCP server to send specific options to different clients from the same DHCP scope.
Plus central administration of DHCP makes it easier to manage. If you have lots of Cisco switches and you create local DHCP scopes on each, surely this is more of a burden to manage than a pair of centrally located DHCP Servers?

HTH

Andy

 

[burtsbees]

Andy---are you talking about passing information for, say, different IP phones and maybe Novell devices? Is this what these "options" are?

Burt

 

[ADB100]

Burt, Sort of.... With VCI's the DHCP Client sends Option 60 which is a text string. The DHCP Server can use this to send specific information to the client. It has two uses - the 1st is you can restrict what information gets sent to the client - for example you might want to disable NetBIOS over TCP/IP for Windows 2000 clients but not for Windows 98 clients. The 2nd is if you have two vendors that use the same Option and you need to send different information to the two different types of clients. For example Cisco Aironet LWAP Access Points use Vendor Option 43 to locate the Wireless Controller, Ericsson IP Phones also use Vendor Option 43 to discover the Voice VLAN and locate their Software Server. Without Vendor Classes you have an overlap here, with Vendor Classes you can send different Option 43 information to different clients in the same DHCP Scope.

If you have access to a Windows 2000/2003 DHCP Server right click on the Server in DHCP Manager and the option 'Define Vendor Classes' is available. Three are pre-defined by default - Microsoft Windows 2000 Options, Microsoft Windows 98 Options and Microsoft Options. You can add your own to this list and they become available when configuring options from the Advanced Tab.

Andy

 

[steyler]

Thanks for the input. At my previous job we had nothing but 6509's at the access layer with Sup32 and also 6509's at the distribution layer running Sup720's. We ran dhcp on the access layer 6509's. In truth, I don't have any idea what a Windows box is capable of in terms of DHCP. I'm curious if they can do reservations for specific machines based on mac address? On the face of it it doesn't seem to me the mac would be sent when using IP helper. So when I have a thousand static NATs for machines and I want ensure each machine retains its IP I create a reservation based on MAC. This spares me from DHCP changing desktop IP's and then having to go through NAT to remove and re-create new NATs. I also think that there could be some benefits when the day comes we start using NAC but I'm not versed well enough in NAC to speak to it. Thoughts?

 

[burtsbees]

Thanks Andy.
Steyler...you had 6509's at the access and distribution layers? What did you have at the core? That's an interesting set up, to say the least...

Burt

 

[brianinms]

DHCP on a Windows Server is a million times better, in addition Active Directory runs a million times better as the DNS table is dynamically populated. In addition you can do a reservation on a Windows server with a few mouse clicks.

 

[steyler]

Thanks for the input guys. We can close this one out.