Layer 2 Switch as DHCP server

[Harsha A.]

Hello All,

I am building a small lab utilizing Collapsed Core Design.

1 Nexus 3548 is acting as a Core Switch and there are multiple 2960x Catalyst Switches acting as Access Switches.

My Nexus Switch is running Layer 3 LAN Enterprise License + Base License and I have noticed that the license does not support DHCP server.

Now I am forced to use 2960x as DHCP server. Is it a good practice to run DHCP server on a Layer 2 Switch ? 

Please let me know your thoughts! 

Regards,

Harsha

[Leo Laohoo]

There's nothing wrong or right in using a 2960X as a DHCP server.  

Personally, I'd choose something as cheap as a Raspberry Pi or Beagle Bone to do DHCP work like in a lab (powered up by the USB port).  

The reason why I'm reluctant to use a switch because sometimes a switch needs to be rebooted or the config gets erased (accidentally).  

[Harsha A.]

Hello Deepak,

Thank you for your input.

Well this is just a lab environment and there are no L1 or L2 Engineers other than me :) 

Hello johnlloyd_13,

This network will run Multicast and since my Nexus 3548 doesn't support DHCP server feature, I had think about using 2960x as DHCP server. (The license I have, supports DHCP Snooping and Relaying and doesn't support Server feature)

Hello Leo Laohoo,

Agreed that Raspberry Pi should suffice in this case, but since this is just a lab environment I am not worried much about the switch getting rebooted.

I tried to lab up this setup and for some reason the DHCP didn't work. Can you guys please go over the config and let me know what did I miss.

L3 Switch is connected to L2 Switch using a Port Channel (LACP Active) and DHCP scope is activated on the L2 Switch. 

Using a Static IP on the client, the client is able to ping the L3 VLAN Interface, but the client is not able to fetch DHCP IP from the Access Switch.

Thanks,

Harsha

[johnlloyd_13]

hi,

is this just a purely layer 2 switching lab? if it's a lab you can configure DHCP on any device (or switch) as long as it's documented for easy and quick reference.

if you're routing between VLANs using a router (or L3 switch), it would be wise to configure DHCP service on a router since all configurations (i.e. IP addressing, VLAN gateway, routing, etc) and troubleshooting are being performed on this device.

[Deepak Kumar]

Hi Harsha,

There is nothing wrong with access switch as DHCP server but many times we need to replace or reboot switch during the down time or in production hours. That may be become a issue with you. otherwise no issue.

And second issue is related to L1 or L2 network engineer rights. Many times we will assign full access to L1 engineer on Access switch. If your Policy allowed to assign rights to L1 engineer then no problem. 

Regards,

Deepak Kumar

www.deepuverma.in