WLAN Controller Link Aggregation in a HA configuration to a Catalyst switch VSS pair

[schuetzm]

Hi,

CVD reg. LAN and WLAN of August 2016 (www.cisco.com/c/dam/en/us/td/docs/solutions/CVD/Aug2016/Campus_LAN_Wireless_LAN_Design_Aug2016.pdf) is recommending the following design (page 31 and 32):

"Spreading the ports from the active and standby WLCs across both switches within the VSS pair. This design minimizes the traffic that crosses the virtual switch link between the Catalyst switches in the VSS pair during normal (non-failure) operation, because both the active and standby WLCs have ports connected to both switches. This design also avoids a switchover from the active WLC to the standby WLC in the event of a switch failure within the VSS pair".

We tried it that way but without success.

Due to that, we went back to use different port-channels between VSS and WLC's:

- Po1 = WLC-primary (Gi 1/1/1, Gi 1/2/1, Gi 2/1/1, Gi 2/2/1)

- Po2 = WLC-secondary (Gi 1/1/2, Gi 1/2/2, Gi 2/1/2, Gi 2/2/2)

The software version of WLC 5508 is 8.0.121.0, VSS is build on Cat 4510R+E running IOS 03.08.02.E.

Did anybody test the recommended design and did it work that way?

Thanks in advance and best regards

Matthias

[Sandeep Choudhary]

Hi,

Yes. LAG with VSS setup, will work as long as the fragments of an IP packet are sent to the same port. The idea is that if you go to multiple switches, the ports must belong to the same L2 “entity” with regards to load balancing decisions.

MOre info: https://supportforums.cisco.com/document/69961/wlc-lag-catalyst-6500-switches

http://www.cisco.com/c/en/us/td/docs/wireless/controller/technotes/8-1/5520-WLC-DG/b_Cisco-5520-WLC-deployment-guide.html

Reagrds

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[schuetzm]

Hi Sandeep,

the VSS/Cat4500 is configured for "src-dst-ip" already. But it didn't work.

Any idea?

Best regards

Matthias

[Sandeep Choudhary]

can you paste the config of the LAG... Regards

[schuetzm]

What part and format reg. config are you looking for (screenshots, GUI or text, interfaces, ...)?

[Sandeep Choudhary]

config on VSS switches (interfaces)

[schuetzm]

Hi,

we're running Po12 with 4 ports to connect WLC-01 and Po13 with 4 ports to connect WLC-02.

The config is:

interface Port-channel12
 description Uplink WLC-01 - Gi1/1/11_1/2/11_2/1/11_2/2/11
 switchport
 switchport trunk allowed vlan 10,38-40,48,500
 switchport mode trunk
!
interface Port-channel13
 description Uplink WLC-02 - Gi1/1/12_1/2/12_2/1/12_2/2/12
 switchport
 switchport trunk allowed vlan 10,38-40,48,500
 switchport mode trunk

!

interface GigabitEthernet1/1/11
 description WLC-01 Port1
 switchport trunk allowed vlan 10,38-40,48,500
 switchport mode trunk
 channel-group 12 mode on

interface GigabitEthernet1/1/12
 description WLC-02 Port1
 switchport trunk allowed vlan 10,38-40,48,500
 switchport mode trunk
 shutdown
 channel-group 13 mode on

Please note: We tried to run all 8 ports within Po12 - but it didn't work that way.

[Sandeep Choudhary]

Yes that right.. you need to use diff port channel for diff WLCs.

Example, port-Channel 12 for WLC1 and PO13 for WLC2

Config is correct and it must work.

*** You can not use same Port channel fro both WLCs.

Regards

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[schuetzm]

Thx - that's what we tested already

So the question is: Why does the CVD tell a different story?

"EtherChannel Port Group Consisting of Eight Ports on Multiple Linecards Across a Catalyst VSS Pair"

"Spreading the ports from the active and standby WLCs across both switches within the VSS pair. This design minimizes the traffic that crosses the virtual switch link between the Catalyst switches in the VSS pair during normal (non-failure) operation, because both the active and standby WLCs have ports connected to both switches. This design also avoids a switchover from the active WLC to the standby WLC in the event of a switch failure within the VSS pair".

[Sandeep Choudhary]

Must need to check...

As per my experience... The right solution is two etherchannels.

Regards

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[Freerk Terpstra]

The picture within the CVD is wrong, you did the right thing. Both WLCs should have their own port-channel because they function in an active/standby setup and you don't want the standby unit to receive the production traffic.

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