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BilalButt62333
Beginner

loop connection

If I attach two switches with two trunk cables whether using both utp or one utp other sfp or both sfp will there be any loop or broadcasting issue or any advantages or disadvantages?

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balaji.bandi
VIP Master

If they are on seperate link as Trunk, due to STP, one link go in to Block Mode  - this setup not suggested until you have any other reason do so. ( you can only use 1 link at a time, until you doing VLAN loadbalance between the link with different STP priroty) more work on cli. hard to maintain consistency.

 

If you bundle them using LACP - this will not cause loops and you can use both the links same time , which increase performance and throughput.

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balaji.bandi
VIP Master

If they are on seperate link as Trunk, due to STP, one link go in to Block Mode  - this setup not suggested until you have any other reason do so. ( you can only use 1 link at a time, until you doing VLAN loadbalance between the link with different STP priroty) more work on cli. hard to maintain consistency.

 

If you bundle them using LACP - this will not cause loops and you can use both the links same time , which increase performance and throughput.

BB

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View solution in original post

BTW, some additional information . . .

With Cisco's PVST (or its rapid variant), you can effectively use both links if you have more than 1 VLAN.  However, generally, as suggested by @balaji.bandi an Etherchannel (LACP) is a better choice.

When using Ethercahnnel (LACP) you may need to configure your "hashing" algorithm to obtain the best (for your traffic) load sharing.  (Older switch's default often is not your best choice, later switch's default, often is the best choice.)

Also, BTW, even with "best" load sharing, any one flow will only use one link and, generally, with dual links, you only get about a 50% bandwidth boost for multiple flows.