WLC network connectivity

[mcaoile]

Hi experts,

Can any of you comment in the attached network drawing.  Is the suggested new wlc connectivity correct.

                  

Regards,

[Sandeep Choudhary]

HI ,

As per my experiences, this design is absolutely right.

When LAG is used, the system dynamically maps the interfaces to the aggregated port channel. This helps in port redundancy and load balancing. When a port fails, the interface is dynamically mapped to the next available physical port, and LAPs are balanced across ports.

https://www.cisco.com/en/US/docs/wireless/controller/6.0/configuration/guide/c60mint.html#wp1277652

Regards

[Vinod Arya · Accepted solution]

LAG simplifies controller configuration because you no longer need to configure primary and secondary ports for each interface. If any of the controller ports fail, traffic is automatically migrated to one of the other ports. As long as at least one controller port is functioning, the system continues to operate, access points remain connected to the network, and wireless clients continue to send and receive data.

When configuring bundled ports on the controller, you may want to consider terminating on two different modules within a modular switch such as the Catalyst 6500; however, Cisco does not recommend connecting the LAG ports of a 5500 or 4400 series controller to multiple Catalyst 6500 or 3750G switches.

-Thanks

Vinod

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[Leo Laohoo · Accepted solution]

It WON'T WORK. 

The WLC can't be connected to two different logical switches with LAG enabled.

LAG has to go to ONE LOGICAL SWITCH.  

Won't work. 

[Leo Laohoo · Accepted solution]

The only way for the bottom drawing to work is when Core Switch 1 and Core Switch 2 are joined together to form ONE logical switch.  An example of this would be VSS (4500R+E or 6500E) or Stackwise (3750/G/E/X, 2960S/X, 3560 or 3850).

[Rasika Nayanajith · Accepted solution]

I agree with Leo, unless your two switches are VSS pair, you cannot have this getting work.

All WLC portchannel interfaces need to terminate on ONE physical switch in all other scenarios.

HTH

Rasika

[mcaoile]

Hi Rasika,

The 2 core switches (Nexus 5K) are not VSS pair.  If I disable LAG in the controller and no port channel in the switch, what will be the consequence, ie, loading, throughput, etc.  The customer wants me to redo the connectivity based on their suggested connection.  Can you suggest of a better connectivity or shall I tell the customer that the existing connectivity is better.

Regards,

[Scott Fella · Accepted solution]

The existing is the way to go. That is the preferred design when you don't have VSS. This is how I deploy:)

Sent from Cisco Technical Support iPhone App

[mcaoile]

Hi Scott,

Is there any documentation that I can show the client that when the WLC links are set to LAG, the links can't be connected to 2 separate switches unless the 2 switches are in VSS?

It is not advisable to remove the LAG links in the WLC, am I right?

Regards,

[Scott Fella · Accepted solution]

It's a good idea and our best practice to keep LAG enabled.  Here is a link that explains LAG and the switch configurations.  It also explains configuration with VSS.  This should help as its a best practice guide.

http://www.cisco.com/en/US/tech/tk722/tk809/technologies_tech_note09186a0080810880.shtml#topic2

http://www.cisco.com/en/US/docs/wireless/controller/7.4/configuration/guides/consolidated/b_cg74_CONSOLIDATED_chapter_0100011.html

Other links to review:

https://supportforums.cisco.com/docs/DOC-23515

Thanks,

Scott

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[mcaoile]

Hi Experts,

Thanks a lot for the advices.

Regards,

Manuelito

[Leo Laohoo]

Wow! 

Thanks a lot for taking the time to rate our posts! 

[devils_advocate · Accepted solution]

The second design is better in terms of resiliency but as mentioned by Leo and Rasika, this will only work if the Core switches are a VSS pair.

Link Aggregation is designed to aggregate (bond) multiple links from one single entity to another single entiry. Generally a single entity is ONE switch or one Router or one WLC but in terms of switches, you can have multiple ports bonded to two Different switches if they are in a VSS because they are still acting as a single entity.

[Vinod Arya · Accepted solution]

At a max you can do is terminating them on two different modules within a single Catalyst 6500 switch provides redundancy and ensures that connectivity between the switch and the controller is maintained when one module fails.

You cannot configure the controller's ports into separate LAG groups. Only one LAG group is supported per controller. Therefore, you can connect a controller in LAG mode to only one neighbor device.

-Thanks

Vinod

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