DHCP and VLANing Question

Skidilliplop · 22 Apr 2009 at 11:49

Good noon to you.

I'm torn whether this should go in enterprise solutions or networks but i'll try here first

I have a load of HP ML350 G4 and G4p servers. They have the HPNC7761 NICs in. I know they support VLAN tagging but what I need to know in order to make a network design decision is how this setup presents to the OS (Server 2003 Standard R2 SP2). Does the NIC just read the tag and ensure replies are tagged to go back onto the same vlan or is it a little more clever than that and does the OS see separate virtual adapters for each VLAN? (as with broadcom BACS) Just need someone that's done it before to say Yay or Nay.

For those that care why....
Situation is one VLAN is becoming two. I have servers that need to talk directly to both VLANs. One of which Provides a DHCP service. One of my primary concerns is whether it can still run DHCP for one of the VLANs but not the other using a single network card. In windows DHCP config I only know of ways to bind DHCP to a NIC not a VLAN. Hence if virtual adapters are created per VLAN setting this up is easy. Else perhaps not.

Tui · 22 Apr 2009 at 18:04

Using HP Network Configuration Utility will create an adapter for each VLAN.

Is it just for DHCP that you are wanting a direct connection? Presumably you will be routing between the two VLANs so you should be able to do DHCP relaying - generally by the router itself, so you just need a DHCP server connected to one of the networks.

Skidilliplop · 23 Apr 2009 at 09:36

Tui said:
Using HP Network Configuration Utility will create an adapter for each VLAN.

Is it just for DHCP that you are wanting a direct connection? Presumably you will be routing between the two VLANs so you should be able to do DHCP relaying - generally by the router itself, so you just need a DHCP server connected to one of the networks.

It's not jsut DHCP, there are other servers hosting other things that need this also. Traditional routing won't work as some of the kit involved has a IP belonging to the other VLAN and this cannot be changed as it's medical kit and getting the vendor out to do it will cost upwards of £1000 unless it's broken. Eventually the subnets will be geographic and proper routing will be used but it's not feasible at present given time scales, costs and the palava of getting 4 or 5 vendors on site at once to make the changes. Not to mention the hours of downtime this will take.

It's a mess

One that I'm cleaning up gradually.

Cheers for the info, I'd figured that'd be the case but worth checking before I report to the board "yes it can be done" and find out it can't.

Confused · 24 Apr 2009 at 16:50

I'm glad you're the one sorting this out and not me!

I sensed from a long time ago this would be a major pain!

Euphoria · 24 Apr 2009 at 21:33

i dont understand how routing will not work, between the VLANS with a single DHCP, aslong as you have the route tables setup and the DHCP, VLAN tagging this shouldnt be a problem. VLANS talking to one another is down to whatever network security you have in place and whether or not you allow this on your network.

I have the one DHCP serving over 32,000 users/ devices over a lot of VLANs (more than 30) and it works fine. If you have the network infastructure in place you can do it within seconds.

But as Tui said the configuration utility will configure the 802.1q on a windows box, you just need to add the vlans which will appear as NICS in your OS.