Cisco Cisco 2504 Wireless Controller 문제 해결 가이드
In current WLC architecture, it is mandatory to map the Wireless Local Area Network (WLAN) to an
interface/VLAN and the default mapping is to the management interface. The limitation is that only one
WLAN can be mapped to a single interface/VLAN. This limitation requires availability of a single large
subnet in dense deployments, which may not be feasible for many users because of existing network design
and IP subnet allocation in their network. Existing features like AP Groups and AAA override may help to
some extent, but are unable to meet the complete requirement and may not be feasible in all kinds of user
deployments. The same limitation also exists in guest anchor setups where guest clients in remote locations
always receive an IP address from a single subnet mapped to a WLAN at an anchor location. Also, an IP
address assignment to wireless guest clients is not dependent on foreign locations and all guest clients at
different foreign locations will get an IP address from same subnet, which again is not feasible for many users.
interface/VLAN and the default mapping is to the management interface. The limitation is that only one
WLAN can be mapped to a single interface/VLAN. This limitation requires availability of a single large
subnet in dense deployments, which may not be feasible for many users because of existing network design
and IP subnet allocation in their network. Existing features like AP Groups and AAA override may help to
some extent, but are unable to meet the complete requirement and may not be feasible in all kinds of user
deployments. The same limitation also exists in guest anchor setups where guest clients in remote locations
always receive an IP address from a single subnet mapped to a WLAN at an anchor location. Also, an IP
address assignment to wireless guest clients is not dependent on foreign locations and all guest clients at
different foreign locations will get an IP address from same subnet, which again is not feasible for many users.
Integration of VLAN Pooling or the VLAN Select feature in release 7.0.116 provided a solution to the
restriction where the WLAN can be mapped to a single interface or multiple interfaces using an interface
group. Wireless clients associating to this WLAN receive an IP address from a pool of subnets identified by
the interfaces in a round robin fashion.
restriction where the WLAN can be mapped to a single interface or multiple interfaces using an interface
group. Wireless clients associating to this WLAN receive an IP address from a pool of subnets identified by
the interfaces in a round robin fashion.
In WLC release 7.2, the VLAN Select feature (which is supported only on the newer WLCs like 5508,
WiSM−2, 7500, and 2500) was modified and now supports VLAN Select with a new modified algorithm. In
the previous implementation, using the round robin algorithm was causing clients to obtain new IP addresses
on every re−association, thus depleting IP addresses fast from the available DHCP pools. The new algorithm
is based on the Clients MAC address and operates in this way:
WiSM−2, 7500, and 2500) was modified and now supports VLAN Select with a new modified algorithm. In
the previous implementation, using the round robin algorithm was causing clients to obtain new IP addresses
on every re−association, thus depleting IP addresses fast from the available DHCP pools. The new algorithm
is based on the Clients MAC address and operates in this way:
When a client associates to a WLAN on a controller, an index is calculated based on the MAC
address of the client and the number of interfaces in the interface group using a hashing algorithm.
address of the client and the number of interfaces in the interface group using a hashing algorithm.
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Based on this index, an interface is assigned to the client.
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Whenever this client joins the controller, the hashing algorithm always returns the same index and the
client is assigned to the same interface.
client is assigned to the same interface.
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If the interface is dirty, then a random index is generated and the interface is assigned based on that
random index.
random index.
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If that interface is still dirty, then a fall back to round robin implementation occurs.
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Note: In order to support the new VLAN Select feature on legacy controllers (such as the 4400 Series, WiSM,
and 2100 Series) with the same MAC−based algorithm, the VLAN Select feature was modified in release
7.0.230 and now operates in the same fashion as release 7.2.
and 2100 Series) with the same MAC−based algorithm, the VLAN Select feature was modified in release
7.0.230 and now operates in the same fashion as release 7.2.
This flow chart illustrates the DHCP address selection when the MAC Hashing algorithm is used in the
interface/interface group configuration:
interface/interface group configuration: