Does this cisco switch support dhcp per vlan basis?

Unanswered Question
Aug 20th, 2010

My goal is to have a switch where each port is an isolated vlan, but where the switch also acts as dhcp on each port/vlan. I understand that this will require a scope being created for every vlan on the switch. That way all guests can connect their ethernet cable, get a dhcp, be secure from all other guests but still have internet access through the same router everyone else is sharing.

Obviously the switch must support 802.1q, but are there any other special requirements in order to have dhcp running on ever single vlan? I have been considering purchasing this SLM2024 switch but must make sure I will be able to do what I wish before buying it

Thanks in advance!

I have this problem too.
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Leo Laohoo Fri, 08/20/2010 - 19:08

My goal is to have a switch where each port is an isolated vlan

I'm no expert of this category of switch but are you talking about Private VLAN?

kyukim Fri, 08/20/2010 - 21:52

Hi, Poul.

1. Yes and No.

    Switch ports in same vlan will talk other.

    If you want, yes you can make each switch port to belong to all different vlans and isolate them, so that your guest can't see each other's traffic.

    But, that requires you need to create 24 vlans, 24 SVIs (interface Vlan for inter-vlan routing) and 24 DHCP pools and you need to create ACL to block each vlan not to talk each other through inter vlan routing.

And, SLM2024 doesn't support SVI. Only MLS switches support SVI. Without SVI, then you need to connect a router on a stick to do inter-vlan routing.

    As leolaohoo mentioned, you can achieve above goals with private vlan to isolate each port to only itself.

    Private vlan makes each port don't talk each other even in same vlan but talk to default gateway.

    But, SLM2024 doesn't support private vlan. You need at least 3550 or above.

2. Yes, you need to create DHCP pool (or scope) for each vlan (or Subnet) on SW to make DHCP server to assign proper address to hosts from each vlan.

3. There is no other requirement for DHCP.

    But, I am not sure if you are going to set up DHCP server on other device as SLM2024 is not running IOS and don' think switch can be a DHCP server.

SUMMARY.

SLM2024 can't achieve your goals by itself. You need a router to do inter-vlan routing and dhcp server role.

You can buy a multilayer SW like CISCO 3550 and it supports private vlan, inter-vlan routing and dhcp server role.

KK

poulwittig1990 Sat, 08/21/2010 - 10:57

Thank you very much for your informative post. I believe the best bang for buck would be purchasing the SLM2024 or similar switch, and upgrading the router to one which would support creating multiple dhcp scopes for each private vlan.

Best Regards,

Poul

Leo Laohoo Sat, 08/21/2010 - 17:41

upgrading the router to one which would support creating multiple dhcp scopes for each private vlan

Routers don't "understand" Private VLAN.  It's the switch.  Cisco Catalyst range of switches will support Private VLANs and multiple DHCP scope without breaking a sweat.  The most affordable one, in my humble opinion, would be the Cisco Catalyst WS-C2960-24TC.  It's a 24-port, 10/100BaseTx with two 10/100/1000BaseTx uplink ports.

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