Руководство По Проектированию для Cisco Cisco Aironet 350 Mini-PCI Wireless LAN Client Adapter
2-19
Enterprise Mobility 4.1 Design Guide
OL-14435-01
Chapter 2 Cisco Unified Wireless Technology and Architecture
Roaming
Layer 3 Roam—Asymmetrical Mobility Tunnel
In a Layer 3 roaming scenario, traffic returning to the wireless client goes through the anchor WLC. The
anchor WLC establishes an Ethernet-over-IP (EoIP) tunnel to forward client traffic to the foreign WLC
where it is then delivered to the client. All traffic originated by the client is forwarded out the
corresponding VLAN interface to which the WLAN is mapped to at foreign WLC. The client's original
IP address and default gateway IP (MAC) address remain the same. All traffic, other than that which is
destined for the local subnet, is forwarded to the default router where the foreign WLC substitutes the
client's default gateway MAC address with the MAC address of the default gateway associated with
dynamic interface/VLAN at the foreign controller.
anchor WLC establishes an Ethernet-over-IP (EoIP) tunnel to forward client traffic to the foreign WLC
where it is then delivered to the client. All traffic originated by the client is forwarded out the
corresponding VLAN interface to which the WLAN is mapped to at foreign WLC. The client's original
IP address and default gateway IP (MAC) address remain the same. All traffic, other than that which is
destined for the local subnet, is forwarded to the default router where the foreign WLC substitutes the
client's default gateway MAC address with the MAC address of the default gateway associated with
dynamic interface/VLAN at the foreign controller.
illustrates a client Layer 3 roam using an asymmetrical mobility tunnel.
Figure 2-9
Layer 3 Roaming
Using
, the following occurs when a client roams across a Layer 3 boundary:
1.
The client begins with a connection to AP B on WLC 1.
2.
This creates an ANCHOR entry in WLC 1’s client database.
3.
As the client moves away from AP B and begins association with AP C, WLC 2 sends a mobility
announcement to its peers in the mobility group looking for the WLC with information for the client
MAC address.
announcement to its peers in the mobility group looking for the WLC with information for the client
MAC address.
4.
WLC 1 responds to the announcement, handshakes, and ACKs.
5.
The client database entry for the roaming client is copied to WLC 2, and marked as FOREIGN. PMK
data (master key data from the RADIUS server) is also copied to WLC 2. This facilitates fast
roaming for WPA2/802.11i clients because there is no need to undergo full re-authentication with
the RADIUS server.
data (master key data from the RADIUS server) is also copied to WLC 2. This facilitates fast
roaming for WPA2/802.11i clients because there is no need to undergo full re-authentication with
the RADIUS server.
Controller 1
Controller 2
190688
LWAPP
LWAPP
LWAPP
LWAPP
Client Database
MAC, WLAN, IP, Sec, ANCHOR...
Mobility
Announcement
Subnet A
Subnet B
AP A
AP B
AP C
AP D
Client Database
MAC, WLAN, IP, Sec, FOREIGN...
Ethernet IP Tunnel
Copy