router or domain controller for DHCP?

[shaferbus]

I'm hoping for some guidance from the masters...

Our network is behind a Cisco 881 router, which currently serves DHCP. I am about to upgrade our server to SBS2010, and I'm wondering if I should have that serve DHCP instead. I thought that made sense since it is also the DNS server for the network.

However, from what I've been able to find online, it seems that Cisco always expects its router to be the DHCP server.

What is the "best practice", and why?

 

[Ali147gta]

Do you mean SBS2011?

SBS also expects for it to be the DHCP server. However you can work around it

You may also get issues with none ms dhcp relay and group policy

http://support.microsoft.com/kb/2459530

Had this and took ages to find the solution

iMachiavellian - think dissident

 

[iggsterman]

Relaying issues will only have to be considered if your DHCP server and client are on different subnets. Otherwise DHCP clients could not care less where they get DHCP handoff. DNS and DHCP services do not have to be and often are not collocated. I'd leave the DHCP with the router as I trust Cisco's implementation more. Matter of opinion of course.

 

[Ali147gta]

Unfortunately that's not true, I've had a client where the group policies were not being applied and the fix was to apply the hotfix as specified in the article above.

DHCP supplied in this case by a watchguard firewall... Installed the patch on the affected machines, hey presto, all decide to work.

I'd normally agree with your statement about leaving DHCP on the router, but when it comes to SBS well, it's just a pain in the neck at times !

iMachiavellian - think dissident

 

[iggsterman]

What is not true, specifically? Also, from the KB article that you are referring to:
[tt]"You may experience this issue if the Windows 7 DHCP client is communicating with a Microsoft Windows-based DHCP Server through a non-Microsoft Relay Agent, such as a Layer 3 network switch."[/tt]
Where is the OP does it say that the traffic is relayed? How does this scenario even apply in their case?

 

[ADB100]

If there is a Windows server there that running DHCP on won't be a burden then I'd use that.
I have two reasons:
Management - in an environment with multiple sites and multiple DHCP servers you can manage them all from the same Windows MMC. Having to telnet around to different routers/switches can be a pain.
DHCP Vendor Classes - Windows DHCP service supports Vendor Classes which make DHCP much more flexible and allows for clients wanting overlapping options - Option 43 springs to mind... IOS doesn't support Vendor Classes.

 

[iggsterman]

This IOS configuration command
[tt]option 43 ascii "Comma Separated IP Address List"[/tt]
takes care of that. I am not going to argue with MS-centric points of view. We run multiple DHCP scopes on IOS equipment. This includes data and voice with all options required to configure the latter. As I said, matter of opinion.

 

[shaferbus]

Wow, thanks for the input!

Yes, I did mean SBS2011... I'm upgrading to Office 2010 and adding a 2008R2 server too, so my head is starting to spin!

We're not running a huge or complex network. A dozen workstations behind the one Cisco router, over a T1. I've got the new server on the network now (different domain name so it doesn't interfere with our old SBS machine). It doesn't seem to be having issues being a DHCP client, but on the other hand it's not the production machine yet!

All things being equal, I'd prefer DHCP on the SBS machine just for the ease of use. However, I'm not entirely sure how to disable DHCP on the router for this subnet without screwing something else up (It doesn't take long to get out of my depth with IOS). We have a DMZ set up on another VLAN that needs addressing, PLUS we use the router for a VPN endpoint, and I'm not entirely sure how the 881 would handle assigning virtual IP's for that with DHCP turned off...

I'm really afraid of opening a can of worms unneccesarily!

 

[tphethai]

this may help DHCP

 

[ADB100]

My comment about Vendor Classes is important if you have devices requesting Option 43 but actually want different data and so you have a clash. Without vendor classes you can't have two different devices request the same option and have different responses. We have Aastra IP Phones and Cisco Lightweight Access points - both expect Option 43 but the data is different for each device.
Vendor Classes work by the client informing the DHCP Server via Option 60 what they are - 'Cisco AP c1130', 'Aastra IP-Phone' etc. With Windows DHCP you can define Vendor Classes for each client type and then configure specific options for each of them even if they overlap.

You can't do this with IOS.

Andy