4-40
Cisco Wireless LAN Controller Configuration Guide
OL-17037-01
Chapter 4 Configuring Controller SettingsWireless Device Access
Configuring Client Roaming
Configuring Client Roaming
The Cisco UWN Solution supports seamless client roaming across lightweight access points managed
by the same controller, between controllers in the same mobility group on the same subnet, and across
controllers in the same mobility group on different subnets. Also, in controller software release 4.1 or
later, client roaming with multicast packets is supported.
You can adjust the default RF settings (RSSI, hysteresis, scan threshold, and transition time) to fine-tune
the operation of client roaming using the controller GUI or CLI.
Intra-Controller Roaming
Each controller supports same-controller client roaming across access points managed by the same
controller. This roaming is transparent to the client as the session is sustained, and the client continues
using the same DHCP-assigned or client-assigned IP address. The controller provides DHCP
functionality with a relay function. Same-controller roaming is supported in single-controller
deployments and in multiple-controller deployments.
Inter-Controller Roaming
Multiple-controller deployments support client roaming across access points managed by controllers in
the same mobility group and on the same subnet. This roaming is also transparent to the client because
the session is sustained and a tunnel between controllers allows the client to continue using the same
DHCP- or client-assigned IP address as long as the session remains active. The tunnel is torn down, and
the client must reauthenticate when the client sends a DHCP Discover with a 0.0.0.0 client IP address or
a 169.254.*.* client auto-IP address or when the operator-set session timeout is exceeded.
Inter-Subnet Roaming
Multiple-controller deployments support client roaming across access points managed by controllers in
the same mobility group on different subnets. This roaming is transparent to the client because the
session is sustained and a tunnel between the controllers allows the client to continue using the same
DHCP-assigned or client-assigned IP address as long as the session remains active. The tunnel is torn
down, and the client must reauthenticate when the client sends a DHCP Discover with a 0.0.0.0 client IP
address or a 169.254.*.* client auto-IP address or when the operator-set user timeout is exceeded.
Voice-over-IP Telephone Roaming
802.11 voice-over-IP (VoIP) telephones actively seek out associations with the strongest RF signal to
ensure the best quality of service (QoS) and the maximum throughput. The minimum VoIP telephone
requirement of 20-millisecond or shorter latency time for the roaming handover is easily met by the
Cisco UWN Solution, which has an average handover latency of 5 or fewer milliseconds when open
authentication is used. This short latency period is controlled by controllers rather than allowing
independent access points to negotiate roaming handovers.
The Cisco UWN Solution supports 802.11 VoIP telephone roaming across lightweight access points
managed by controllers on different subnets, as long as the controllers are in the same mobility group.
This roaming is transparent to the VoIP telephone because the session is sustained and a tunnel between
controllers allows the VoIP telephone to continue using the same DHCP-assigned IP address as long as
