Bounce ports on VLAN change

[sebschrader]

On VLAN change usually the IP network of a client changes and the client is supposed to request a new IP address via DHCP. A VLAN change however is transparent for the client and occurs only on the NAS (switch). By bouncing the port (disabling and re-enabling the client's port on the switch after the a few seconds) the client will typically perform a new DHCP request.

There are several ways to do this

• The port can be disabled and enabled by a management API of the switch (e.g. via SNMP IF-MIB::ifAdminStatus messages)
• Some vendors have implemented vendor-specific RADIUS attributes that can be provided in RADIUS Change-of-Authorization (CoA) messages:
  • HP provides HP-Port-Bounce-Host
  • Cisco provides the value subscriber:command=bounce-host-port for its Cisco:Avpair attribute.
  • ALE devices can automatically perform a port bounce, if they detect a VLAN change due to an CoA message