Bootprelay configuration

  • 0
  • 1
  • Question
  • Updated 7 months ago
  • Answered


We have a D series Extreme switch and would like to enable bootprelay so clients can receive their addresses from the companies DHCP server.

I see the commands are (assuming just the default vlan is configured)

 "configure bootrelay add <dhcp_server_ip>"

"enable bootprelay vlan"

However the document also says the VLAN must have an ip address and IP forwarding must be enabled which is where I am confused.

This device will not be routing, just acting as a simple switch. Do I need to configure IP addresses and IP forwarding to make Bootprelay work when the device is not being used as a router?



Photo of laurie


  • 90 Points 75 badge 2x thumb

Posted 7 months ago

  • 0
  • 1
Photo of Ram

Ram, Employee

  • 1,450 Points 1k badge 2x thumb
The following KB Article would help us on How to configure Bootprelay using EXOS:-

Bootprelay needs to be enabled on the switch that is routing. As long as the device has L2 connectivity up to the routing switch bootprelay will take over from there.
Photo of Pala, Zdenek

Pala, Zdenek, Employee

  • 7,974 Points 5k badge 2x thumb
What is the switch type? You mentioned D (enterasys operating system), but commands are for X series (exos operating system)
Photo of Frank


  • 3,490 Points 3k badge 2x thumb
As far as I understand it, if you're not routing, then you don't need to configure bootprelay. I'm assuming that the clients are on the same network/vlan as the server.
Photo of Patrick Voss

Patrick Voss, Employee

  • 11,214 Points 10k badge 2x thumb
Hello Laurie,

To confirm what Ram and Frank said you do not need to configure bootprelay on a switch that is not routing. The discovers will make it to the routing device via L2 and that device should be the one configured to absorb the discovers to be relayed to the DHCP server.
Photo of Paul Thornton

Paul Thornton

  • 1,324 Points 1k badge 2x thumb
Following on from what others have said - bootprelay (or any other form of 'dhcp helper' technology) is fundamentally an L3 function, and needs to run on the router of the network not a an L2-only switch.

Clearly if that switch has IP addresses, and is routing, then it is the right place for this to be applied - but it sounds like in your case you need to enable it on whatever device is the default router for your VLANs.
Photo of laurie


  • 90 Points 75 badge 2x thumb


Thanks for the replies. I now understand that bootprelay is an L3 function.

The default router for this network is an externally managed device so we were hoping to configure the Extreme device with the bootprelay function since we mange this device ourselves.

Would it be possible to do the following to achieve what we want?

1) Configure Extreme device with ip address and give it a gateway address of the managed router (

2) Configure vlan "VLAN2" add ports 1 - 12 untagged

3) Configure vlan "VLAN2" ip-address

4) Enable ipforwarding "VLAN2"

5) Enable DHCP Relay

6) Enable bootprelay vlan VLAN2

7) Configure bootprelay add <dhcp-server>

8) Setup new scope for

9) Configure dhcp parameters on MS dhcp server
   003 Router set to  (ip address of extreme switch)

Photo of Matthew Hum

Matthew Hum

  • 362 Points 250 badge 2x thumb
The D2-series is a L2 switch only. in addition it runs EOS, not XOS, so those are not options for you. If you are insistent on running your own DHCP server there are some different options for you.

1. you could pass a tagged/trunked link to your server.
    a. enable VLAN 802.1Q tagging to your interface
    b. enable NIC teaming on the interface and create new interfaces on each tagged VLAN
    c. enable additional scopes in your DHCP server

2. have an existing linux server on a trunk link and use dhcrelay to forward the DHCP requests to your windows DHCP server (or have linux handle the DHCP server with dhcpd)

3. get an additional L3 switch trunked with all your VLANs and enable bootprelay/ip-helpers on that.
Photo of laurie


  • 90 Points 75 badge 2x thumb
Hi Matthew

You're completely correct. This was mentioned earlier and I should have chased that down before continuing. Thanks for explaining the problem at a beginner level.