what's the algorithm for interface groups assingments on wlc 5508?

[victorcossio]

I'm trying to find a trustworthy source about the assignment algorithm of wireless traffic when many wireless clients send traffic to WLAN associated with an interface group, let's say with 4 VLANs. 

the documentation below doesn't say anything about which algorithm is used. is round-robin? hashing of some form(with MAC/IP)? what else?

https://www.cisco.com/c/en/us/td/docs/wireless/controller/8-5/config-guide/b_cg85/ports_and_interfaces.html#interface-groups

I hope you can clarify this.

greetings.

[jagan.chowdam]

Refer "Interface Group" section from the link. It is round robin fasion.

https://www.cisco.com/c/en/us/td/docs/wireless/controller/8-10/config-guide/b_cg810/ports_and_interfaces.html

• Upon a client's connection to a WLAN managed by a controller, a hash index is computed utilizing the client's MAC address and the interface group's quantity of interfaces.

• This index dictates the assignment of an interface to the client.

• Upon subsequent connections to the controller, the hashing algorithm consistently yields the same index for the client, ensuring assignment to the same interface.

• In cases where the designated interface is marked as "dirty," a random index is generated to facilitate interface assignment.

• Should the designated interface remain in a "dirty" state, a fallback to a round-robin approach is enacted.

Jagan Chowdam

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[victorcossio]

Jagan

I am bit confused by your answer. you claim that is round robin but the description below clearly states it as hashing with MAC. 

so which one is the verdict?

also. the link you are referring to doesn't contain the information you provide. with a quick Ctrl+F search for you will see this. where did you get the information in your answer?

thanks in advance.

[Rich R · Accepted solution]

See https://www.cisco.com/c/en/us/td/docs/wireless/controller/technotes/8-6/b_Cisco_Wireless_LAN_Controller_Configuration_Best_Practices.html#concept_4CBC85029ED6485984F92D8D460E2015
It uses hash by default but can switch to round robin as noted.
Also note the feature was previously called VLAN Select.

[eglinsky2012]

Regarding hashing the MAC address to preserve VLAN assignment, does this work with multiple WLCs (including a mix of 9800/8540) in a mobility group? For example, if a client on WLC 1 later joins WLC 2 (whether it's another 8540 or a 9800), will WLC 2 assign the client the same VLAN as WLC 1 did?

[Rich R]

At a guess I would say 2 8540's with identical configuration, yes.
I'd be very surprised if you got the exact same result with 8540/9800 - if you want to do it then test thoroughly.