VLAN Question 1

[Molenski]

Hi there,

First of all, I've been in IT for about 5 years but only dealt with software; building servers etc. I was really bored of this and decided to do my CCNA which I passed last month. Luckily, I've managed to get a transfer over to our comms team to get some actualy experience. So basically, I'm a complete newbie but looking forward to getting involved.

With this in mind, and also with the fact that we work on secure networks which are built to a specification we don't get involved with there is a slight problem. I would like to look at implementing VLANs at a few of our sites (6 or 700 users and a fair amount of switches). Only problem is, we have one DHCP scope and one DHCP server. We can't change this. So I was (in my novice way) thinking, we could maybe use VLSM and somehow create VLANs that way. Not sure how to go about it, I suppose in the real world you would use static IP or multiple DHCP servers? Can anybody give me some advice? Sorry if this thread is a bit burbled but I really am just starting out!

Cheers in advance.

Molenski
As my bessie bud Kev always says - Get involved!!!

 

[baddos]

You would still need another DHCP scope or server to support the added subnets. You don't want to assign 700 hosts addresses manually do you?

 

[Molenski]

Appreciate that this would be a terrible idea but isn't there some sore of command that I can use to point workstations to the DHCP server on another subnet? Isn't there an IP-Helper command that can be used? Any advice would be cool.

Molenski
As my bessie bud Kev always says - Get involved!!!

 

[chieftan]

Primarily you would be looking at having to impliment something at layer 3.
IP Helper addresses are used for a layer 3 device to forward broadcasts (Layer 3 is designed to stop this normally).
You could also use a relay agent (BootP).

DHCP DSC is a broadcast and any DHCP that can hear responds.

 

[Molenski]

OK, thanks for your help on this. Not really sure exactly where to go from here but I'll keep pluggin' away!

Molenski
As my bessie bud Kev always says - Get involved!!!

 

[vipergg]

You would indeed use helper addresses at the layer 3 interface for each subnet , this helper address would be the address of your dhcp server . A dhcp request starts as a broadcast , with the helper address configured this converts this request to a unicast to the dhcp server.

 

[Molenski]

OK, I understand this a bit more now I think. Don't suppose you have a link to a page with detailed info on how I'd carry this out do you? Would be great if you have.

Cheers.

Molenski
As my bessie bud Kev always says - Get involved!!!

 

[chieftan]

Try the following, it may explain a bit more

http://www.ciscopress.com/articles/article.asp?p=330807&seqNum=9&rl=1

 

[Molenski]

Thanks a lot, really appreciate your help on this!

Molenski
As my bessie bud Kev always says - Get involved!!!