Spanning tree Questions

[Markii_2430]

I have this network topology, I have Catalyst 3750X-12S-S as the Root and Catalyst 2690 for Access. 

Our main goal is to have a redundant link or connection if for example the one of the catalyst 2690 link is down we can have link that will cover or back up link. i know STP can do that but i need to know it from experts. or does any other option than STP?

And also i know my devices are old any recommendation new switches than can support our goal?

[Reza Sharifi]

Hi,

Use Portchannel instead. Put every 2 links from each 2960 in a Portchannel. This way, you don't need to worry about STP, use both links and you also have redundancy in case one of the links fails.

https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3750x_3560x/software/release/12-2_55_se/configuration/guide/3750xscg/swethchl.html

HTH

[Markii_2430]

Thanks for the reply, so its better to use PortChannel rather than STP?

When I configure portchannel how does STP? automatic disable ?

also any recommendation switch for my setup?

thank reza

[Reza Sharifi]

Thanks for the reply, so its better to use PortChannel rather than STP?

You still need to configure STP just in case there is a loop in the network but STP will not be blocking one of the links.

When I configure portchannel how does STP? automatic disable ?

You can configure the Portchannel with LACP or simply mode "on". As for STP, just make the core switch the root and leave the priority for all the access switches as default.

also any recommendation switch for my setup?

That depends on your budget. Older switches are usually cheaper.

HTH

[paul driver]

Hello

I would agree a port-channel is the best option however you do have another option given the make /modal of thoese devices , You could also use a flex-link, this would allow one uplink to be active and ther other become a backup link ( no stp)

[Mohsin Alam]

Your best bet is port channels , as it not only reduces STP instance but also provides you load balancing as well so that you are able to fully utilize all the links in the network. 

How are you avoiding STP in your case?
You basically have 2 links from core switch , where 1 is blocked due to STP loops.
Once you bundle in port channel it is physically 2 but the switch see's it as one single link so no more STP ! 

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[Elliot Dierksen]

I totally agree on the port channels. I would add one other suggestion. Use LACP (preferred) or PaGP to add the ports to the link, do not add them statically. The reason for this is that when it is statically assigned, the switch will immediately start trying to distribute traffic over that link. If the other side isn't fully yet and ready to receive traffic, you could be dropping some of your traffic into a bit bucket. If you use a protocol to add the member to the port channel, it won't be added until you know the other side is ready to receive and process it.