L2 links redundancy on cisco 3850

[Muhammad Tanveer]

Dear all,

We have three L2 links between two sites all these links are terminate on Cisco-3850 both sites.

Currently we configured Flex link (for redundancy on two links) and third on is administratively down once these two links go down at time, we shift the traffic on third one which is administratively down. 

Which is considered as a constraint for the management and also we are wasting the bandwidth of third link.

Please suggest the way how can we use three links simultaneously and use max bandwidth with redundancy.

Please find attached diagram.

Regards,

[Georg Pauwen]

Hello,

Flexlink is probably not the best solution, as it will allow only one active and one backup link, hence effectively using only one of the three links you have available. I am sure you have already considered this, but why not simply configure a port channel using all three links ?

[Leo Laohoo]

Muhammad,

Why did you delete your previous thread of the same topic?

[Giuseppe Larosa]

Hello @Muhammad Tanveer ,

as already noted a port -channel of the the three links is the best choice to maximize all links usage and still have redundancy.

I strongly recommend to use LACP on the member links, but LACP frames can be allowed or not depending on the type of service you have bought from the provider.

So checking with the provider if LACP can travel on links is a wise step.

For EoMPLS pseudowires or other type of MPLS based L2 services it should not be a problem. However, in case of 802.1Q tunnleing the provider may need to enable L2 protocol tunneling.

Hope to help

Giuseppe

[Muhammad Tanveer]

Dear Guseppe,

Hope you will be fine and enjoying good health.

Thanks for your time, We would like to bring your notice EtherChannel didn't work for us. We will welcome if you will guide us for an alternate choice in our scenario. Hope you will come up with some more workable solution.

Thanks with regards.

[Muhammad Tanveer]

Dear Guseppe,

We are planning to implement EtherChannel today after business hours, let me confirm that L2 links (provided by ISP's) are NNI form both ISP's weather it works please share your feedback as soon as possible.

Regards,

[Joseph W. Doherty]

I "see" your links have different bandwidth capacities. Assuming both that you have multiple VLANs and that STP works, using Cisco's PVSTP or MST, you can select which VLANs use which link (which might be based on their overall link usage and/or by how "important" their traffic is).

[Muhammad Tanveer]

Dear Joseph,

In our environment all these links are terminated on single switch and part of single vlan as access ports on both sides. Please suggest....

[Joseph W. Doherty]

With a single VLAN, and without Etherchannel being an option, I cannot think of other L2 options, on two distinct L2 switches, to use those links, concurrently, beyond, perhaps, some kind of 3rd party MUX.

The only other thing that pops to mind might be whether a virtual stack (if supported) might be supported between the two switches using those links.