How to configure ‘DHCP option 43’ on Enhanced Layer 2 Software (ELS)

The DHCP Option 43 feature helps the Access Point (AP) to associate with the Wireless controller (WLC) in an L3 environment (AP in one network and WLC in another network). The AP boots up, performs POST, then sends a DHCP request.
The switch sends out a DHCP offer; an IP address to use, a default gateway to use, and also the 43 TLV option. The TLV contains the IP address of the WLC, with which the AP needs to be associated.
The ‘byte-stream’ option is not available on ELS. Users need to configure the DHCP option 43 instead.
CLI (legacy DHCP server)
set system services dhcp option 43 byte-stream “105 112 58 49 48 46 50 53 53 46 50 48 56 46 49 48 44 49 48 46 50 53 53 46 50 48 56 46 49 49”
ELS DHCP server
Option 1:
set access address-assignment pool VLAN-POOL family inet dhcp-attributes option 43 string ip:20.0.0.10,20.0.0.11
Option 2:
set access address-assignment pool DHCP-POOL family inet dhcp-attributes option 43 hex-string 69703A32302E302E302E31302C32302E302E302E3131
Example:
Single IP defined for option 43 as “20.0.0.10” (ip:20.0.0.10 / 69703A32302E302E302E3130) / http://www.asciitohex.com/
Multiple IP defined for option 43 as “20.0.0.10” and “20.0.0.11”(ip:20.0.0.10,20.0.0.11 = 69703A32302E302E302E31302C32302E302E302E3131 ) / http://www.asciitohex.com/
Option 2 is used to define option 43 in the following example:
Topology : [ WLC ] (20.0.0.10 ) —– V20 —- [ QFX3500 ] —– V10 —- [ AP ] Example : Single IP defined for option 43 as “20.0.0.10”

Example : Multiple IP defined for option 43 as “20.0.0.10” and “20.0.0.11”

 

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James Palmer

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