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© 2008 Cisco Systems, Inc. All rights reserved. IUWNE v1.0—2-1
Basic Cisco WLAN Installation
Roaming
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Mobility Groups, Mobility Domains
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Controller > General
A Cisco Wireless LAN Controller (WLC) can only reside in a single mobility group.
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Controller > Mobility Management > Mobility Groups
There are two methods to define the mobility group: Add a member using either the New or Edit All option, in which all members are represented in a text format.A controller can know members of other mobility groups.
© 2008 Cisco Systems, Inc. All rights reserved. IUWNE v1.0—2-5
Roaming Concept
Roaming refers to movement of clients across Cisco APs while transmitting
Roaming can occur across different mobility groups, but must be within a mobility domain
The Cisco WLC can reside in only a single mobility group The following should be consistent for mobility groups:
– Mobility group membership
– Code across all member controllers
– LWAPP mode across all member controllers
– ACLs configured on all member controllers
– WLAN configuration
– Virtual IP address Two types of roaming
– Intrasubnet roaming (Layer 2)
– Intersubnet roaming (Layer 3)
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Cisco Wireless Layer 2 Roaming
Single Cisco WLC
Multiple Cisco WLCs in the same subnetwork
Transparent to the client
The session is sustained during connection to the new AP
The client continues using the same DHCP-assigned or static IP address
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Client Roaming Within a Subnetwork
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Cisco Wireless Layer 3 Roaming
Multiple Cisco WLCs in different subnetworks
Transparent to the client
The session is sustained during connection to the new AP
Tunnel between the anchor Cisco WLC and foreign Cisco WLC along with special handling of the client traffic by both controllers allows the client to continue using the same DHCP or client-assigned IP address while the session remains active
Set up via either a symmetric or asymmetric tunnel
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Client Roaming Across Subnetworks
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Roaming Example—Preroaming
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Roaming Example—Layer 3 Asymmetric
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Roaming Example—Layer 3 Asymmetric (Cont.)
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Roaming Example—Layer 3 Symmetric
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Roaming Example—Layer 3 Symmetric(Cont.)
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Symmetric or Asymmetric Tunnelling
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Roaming: Tunnels (Symmetric Example)
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Cisco Wireless Mobility Anchor
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Cisco WirelessMobility Anchor Considerations
A foreign session to the anchor is set up ahead of client IP address determination.– The foreign controller will have no knowledge of Layer 3 client
information.
Web authentication is supported, but authentication will occur on the mobility anchor as opposed to the local controller.
This mobility anchor function is only available on Cisco 4400 Series Wireless LAN Controllers and Cisco WiSM blades.– 2100/WLCM can be foreign controller, but not anchor the guest
tunnel.
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WLANs > Mobility Anchors
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Controller > Mobility Management > Mobility Anchor Config
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Summary
Controllers can be part of the same mobility group, which allows them to exchange information about clients.
Roaming occurs when a stations changes connection point while transmitting.
At Layer 2, credentials are passed from one controller to the other to ensure seamless mobility.
At Layer 3, roaming can be symmetric or asymmetric, to maintain the client IP address or complete connection to the original subnet.
When roaming is asymmetric, the mobility anchor feature allows a partial symmetric configuration based on the WLAN.
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