Network Looping Help

[dinesh.manral]

Hi,

Currently we are having looping issues where two sites are connected through fiber and backup radio connection (diagram beneath). We want a scenario where switchports (for both switches Cisco 350x and C3850) connected to both Radio and fiber should be in active-active state.

Currently the port connected to Radio is in administrative down state, and we are bringing it up in the event of outage with fiber. You are requested to help and advice how we can achieve always on status for the switchports connected to both Radio and Fiber.

Best Regards

Dinesh Manral

[balaji.bandi]

With the L2 config you can not acheive with the setup you looking to do, the STP block the ports.

Are you looking only L2, if not you can use L3 make it L3 p2p interface and run IGP to Load-balance the Links

or if you looking only L2, Use different VLAN each Links with STP Priorities.

Take example :

Wireless Port - Trunk allow , 10, 30, 50 ( odd VLANs) with priorty XXX

Switch to Switch - Trunk Allow , 20, 30,40 ( even  VLAN) with Priorty YYY

So only respect VLAN will be blocked.

Make sense ?

[dinesh.manral]

Thanks Balaji, will perform the respective test during weekend.

[paul driver · Accepted solution]

Hello
Then you need to make sure spanning-tree is active for the vlans these ports are assigned to, Even though the ports physical state would be active the stp state on the non root switch non designated port would be in a stp blocking state

[dinesh.manral]

Thanks Paul, will perform the respective test during weekend. Will let you know the outcome.

[Oleg Volkov · Accepted solution]

Hi.
Best practices is migrate from L2 to L3.
But if it not possible, one way is use STP or use PortChannel.
PortCannel member must be same speed.
If you use STP (rapid pvst) one port will be Alternative. You can create one additional VLAN and add it only to trunk in radio link. Add SVI to each 3850 in this VLAN and config IP SLA monitor. After this, You can see state of Your radio link

[dinesh.manral]

Thanks Oleg and solution provided by you and Paul worked perfectly. We used STP and configured 3850 as root switch for the particular VLAN. The traffic is moving and failover is automated.

[dinesh.manral]

Thanks Paul and solution provided by you and Oleg worked perfectly. We used STP and configured 3850 as root switch for the particular VLAN. The traffic is moving and failover is automated.