Redundant connection between switches in different domain

[santoshd.90]

Following is the scenario for me.

Customer B DataCenter is connected to internet through Customer A's internal network. A cable connection is present between Switch A (Customer A) and Switch B (Customer B DC). Both ports at both end are configured access port and spanning tree is disabled between them.

Now i want to add another connection for backup should the primary link goes down. What are to be considered from spanning tree perspective as the two switches are managed by different customers.

Thanks
SAN

[Reza Sharifi]

If each customer can agree on the setup and if both switches are Cisco, Etherchannel is one option.  This way you can use both connections and no link is blocked, if not you would have to turn on STP for both primary and backup links and STP will block one and if one goes down the other one will take over packet forwarding.

HTH

[Joseph W. Doherty · Accepted solution]

. . . you would have to turn on STP . . .

If you don't like a STP variant, depending on your equipment's features, Cisco's FlexLink or REP might be other possibilities.

[santoshd.90]

Thanks for mentioning those alternatives to STP. 

Do they require any specific licenses or IOS versions or Switch models ??

[Reza Sharifi]

Flex Link is Cisco proprietary protocol that was invented back in 2006/2007. Have not seen many deployments and not every Cisco switch and Cisco IOS supports it. 

Good Luck.

[santoshd.90]

In case of etherchannel , is it possible to configure in two switches from one customerA to a switch from customerB or vice versa??

And also is it possible to enable etherchannel on access ports ??

[Tausif Gaddi]

For Configuring Spanning Tree Protocol (STP) on Catalyst Switches, here is a good document.
http://www.cisco.com/c/en/us/support/docs/lan-switching/spanning-tree-protocol/5234-5.html#background