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Professional Discussions => Routing and Switching => Topic started by: ptm82379 on August 25, 2016, 08:14:51 AM

Title: SFP ports as trunk in mixed environment
Post by: ptm82379 on August 25, 2016, 08:14:51 AM
Hello all, this is my first post. I am getting back into networking after quite a while away from the game so go easy on me.

Our environment has 3 switches, Our core is a cisco SG-500-28p, the others are an HP v1910-48G, and a linksys SRW2024p.

I want to know the best way to connect these switches for redundancy and speed if possible. I realize that may be 2 different answers.

I will also need to know if spanning tree protocol will need to be used vs LACP ect for the best solution because I am very new to using those.

I am attaching a document to show some examples but they will basically be variations using the SFP ports or standard ports. Again these may not even make sense so go easy on me please.

The srw2024 has 2, 1 gigabit SFP ports

The sg500-28p has 4, 10gig SFP ports

The V1910-48G has 4, 1gig SFP ports

I am only assuming here but I believe the speed can be set or will auto negotiate down on the SG500 SFP ports

Would there be an advantage to using the SFP ports vs a pair of standard aggregated LACP ports? Both the SFP and standard ports are 1 gigabit.

Take a look at my crude drawings, please show me what I missed and what I clearly do not understand so that I can make this work.
Title: Re: SFP ports as trunk in mixed environment
Post by: deanwebb on August 25, 2016, 09:57:15 AM
EPIC first post, dude. Welcome aboard!

Sadly, I'm a security guy, so I'll have to leave your answer to the switching guys. Pretty sure you want STP running, though, because I remember horror stories from other guys here when it was turned off. Something about broadcast storms and the whole network collapsing in a smoking ruin.
Title: Re: SFP ports as trunk in mixed environment
Post by: ptm82379 on August 25, 2016, 10:18:15 AM
Thanks!

Yes i was figuring STP will need to be enabled with the core set to root bridge but I was not sure whether to enable it on the edges. My assumption was yes but we all know where those get us.
Title: Re: SFP ports as trunk in mixed environment
Post by: ptm82379 on August 25, 2016, 10:45:03 AM
Here is another one that I found that may make more sense.

Would I need STP enabled on all 3 switches and the root bridge set to the core switch or just STP enabled on the core?

I would use LACP to aggregate the ports for interconnection between switches
Title: Re: SFP ports as trunk in mixed environment
Post by: wintermute000 on August 25, 2016, 04:09:53 PM
Turn it on for all switches , set root and you'll be fine. Check out portfast for access ports. That's pretty much all you need without getting into the fancy stuff.
Make sure they're all running thr same stp mode
Title: Re: SFP ports as trunk in mixed environment
Post by: Dieselboy on August 26, 2016, 05:25:15 AM
Welcome!

STP detects L2 loops. Depending on which STP version are available on those devices you probably can only enable STP on VLAN 1. But the benefit of having STP enabled on even on a single-switch network is that if somehow a cat6 cable accidentally gets plugged back into the same switch, then it will not bring the entire switch down; because STP will detect it and block one switch port.

If you use LACP to link the core switch to each additional switch then technically there are no loops (the core will have 2 LACP links, one to each switch. Each LACP bundle is seen as one link) so technically as there are no loops you don't need STP. Unless you use 3 LACP links, and make a triangle out of your network then you will need STP to block one of the LACP links.