Cisco Cisco Aironet 350 Mini-PCI Wireless LAN Client Adapter Design Guide
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Enterprise Mobility 4.1 Design Guide
OL-14435-01
Chapter 2 Cisco Unified Wireless Technology and Architecture
Roaming
6.
A simple key exchange is made between the client and AP, the client is added to WLC 2’s database,
which is similar to the anchor controller’s entry, except that the client entry is marked as FOREIGN.
which is similar to the anchor controller’s entry, except that the client entry is marked as FOREIGN.
7.
Data being sent to the WLAN client is now EoIP tunneled from the anchor WLC to the foreign WLC.
8.
Data sent by the WLAN client is sent out a local interface VLAN at the foreign controller.
The 'asymmetrical' Layer 3 roaming procedure described above solves the challenge of roaming
transparently across Layer 3 boundaries; however, the asymmetric flows can cause other issues in the
upstream network. This is especially true if wireless client traffic is expected to flow bi-directionally
through adjacent appliances or modules such as firewalls, NAC and or IPS/IDS appliances. Or, for
example, if uRPF checks are enabled on next hop routed interfaces, traffic is dropped after the client
roams to a different subnet. This is the reason why a symmetrical mobility tunnel capability was
introduced to the Cisco Unified Wireless solution.
transparently across Layer 3 boundaries; however, the asymmetric flows can cause other issues in the
upstream network. This is especially true if wireless client traffic is expected to flow bi-directionally
through adjacent appliances or modules such as firewalls, NAC and or IPS/IDS appliances. Or, for
example, if uRPF checks are enabled on next hop routed interfaces, traffic is dropped after the client
roams to a different subnet. This is the reason why a symmetrical mobility tunnel capability was
introduced to the Cisco Unified Wireless solution.
Layer 3 Roam—Symmetrical Mobility Tunnel
Beginning with WLC Release 4.1 and later, the WLCs can be configured to support dynamic,
bi-directional tunneling between the foreign AP/WLC and the anchor WLC as shown in
bi-directional tunneling between the foreign AP/WLC and the anchor WLC as shown in
.
Figure 2-10
Layer 3 Roam—Symmetrical Mobility Tunnel
The WLC's Layer 3 mobility handoff procedure remains unchanged. However, WLC Release 4.1 makes
use of existing capabilities associated with the solution's auto anchor tunneling mechanism to create a
dynamic symmetrical tunnel when a client performs a Layer 3 roam.
use of existing capabilities associated with the solution's auto anchor tunneling mechanism to create a
dynamic symmetrical tunnel when a client performs a Layer 3 roam.
Controller 1
Controller 2
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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
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