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Getting DHCP Option 43 to work with Juniper EX/SRX and Aruba

Hi,

 

I was setting up a new 3400 Controller and was looking into using DHCP Option 43 for Aruba AP Controller Discovery. I found a great tech document discussing DHCP Option 43 when you are using Microsoft/Linux DHCP Server's but there is nothing out there discussing how to get it to work with Juniper.

 

In our enviorment, we are using a Juniper EX3300 switch in Stack as our Office core switch and also as our DHCP server. I was able to get the DHCP Option 43 to work and I thought I would share it with you all.

 

This is applicable to SRX Series firewalls running DHCP as well.

 

Here is a command you would use to  configure option 43 on a Juniper:

 

juniperswitch# set system services dhcp option 43 byte-stream "hexadecimal string"

 

The "hexadecimal string" consits for three parts - Type + Length + Value.

 

For Aruba or Cisco - the Type field is always - 0xf1.

 

The Length field is the number of Controller Managememnt IP addresses multiplied by 4 in Hex. In our case there was only one Controller Management IP address so, the Length field is - 1 * 4 = 4 = 0x04.

 

The Value field is the IP address of the Controller in Hex. In our case, the IP address was 10.0.192.25 which translates to 0x0a 0x00 0xc0 0x19.

 

So the command you would add to your DHCP scope configuration is:

 

juniperswitch# set system services dhcp option 43 byte-stream "0xf1 0x04 0x0a 0x00 0xc0 0x19"

 

One other thing you may want to remember is to specify this DHCP option under the same DHCP scope/VLAN in which your AP's reside.

 

Here is a Juniper KB document discussing what I have explained above for Cisco. But it works with Aruba as well.

Valued Contributor II

Re: Getting DHCP Option 43 to work Juniper EX/SRX and Aruba

Hi Anup.

 

Published very usefull article. thanks :)

Cheers,
Venu Puduchery,
[Is my post helped you ? Give Kudos :) ]
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