2x Sg300-20 and one 28p redundant ring on fibre

[miroslaw len]

hello,

I have got one sg300-28p and two sg300-20 switches as core of my mid-size network.

Currently Iam thinking about modernization classic ethernet uplinks which is too low in quantity, and we have problems with redundancy.

So I have thought that we can use two fiber cables (separate, on two different paths):

the main goal will be redundancy and higher the bandwith of uplinks. I thought that miniGBIC gives me 1gb bandwith each one.

At the draft below I have marked planned setup and I would like to ask you for any advices.

   _________(about 100m)_______                 <1st fiber cable

   |                                                |                     <1st fiber cable linked two first miniGBIC port on all switches

sg300-20 ----- sg300-20 -----sg300-28p       < 2nd fiber cable linked in second miniGBIC ports on all switches

And the most important - how can I avoid loops? Spanning tree is not best protocol I suppose?

What is the Unidirectional Link Detection (UDLD) ?

Is that possible to get redundancy and bandiwth increase at the same time?

Thank you

M.

[Michael Swenson · Accepted solution]

Hello,

You could change to fiber but this will not help the bandwidth.  A 1Gig copper cable has the same bandwidth as a 1Gig fiber cable.  Fiber help when you cable runs are longer.  However it appears you cable runs are less then the 300 foot limit for copper.

The Best way to add speed and redundancy would to to setup LAGs ( port channels) between.  Thus you would have 2 or more copper cable runs between switches setup in a LAG.  The LAG of 2 or  more ports combines those ports into one interface.  This does not double the bandwidth to 2Gig.  However the switch will load balance the ports in the LAG for better performance.  Furthermore if one of the port / cables fail in the LAG the other will continue to work. this will give you the redundancy.

UDLD in a Fiber connection protocal.  Fiber cables have two cables, one to sending and one for receiving.  If one of the sides of the cable fails, UDLD will detect the failure and shut down the link so you do not get one direction traffic.

Best Regards,

[miroslaw len]

hello

thank you for your reply,

As I understand - there is no any specific solution which allow avoiding loops in my case (when making a loop by fiber cable)?

So i should break the loop and manually reconnect when needed?

is there a possibility to make the fibre ports as LAG?

is there an iOs on this switches (and configuratkon like on Cisco pro routers / switches)?

regards

m.

[Michael Swenson · Accepted solution]

Hello,

Actually if you connect the devices on a loop, Spanning tree will shut down one of the link to prevent the loop.  This is enabled by default. Then if a link in the loop fails, Spanning Tree will adjust the topology and enable the blocked port.  This can give you redundancy.

The 300 and 500 level switches do have a form of IOS.

Fiber port can be in a LAG.  However, you can not have a copper port and a fiber port in the same LAG

Best Regards,

Mike

[miroslaw len]

Thank you for your answer ! :)

So, assuming if  I would have two fibres  I should make one LAG on both fibre ports and don't fight with Spanning Tree ?

Is this a correct solution? Or maybe there is possible to create it better?

Is that config will not lock any other features availiable in this switches?

Thank you :))

[Michael Swenson]

Yes, By having the 2 fiber ports in a LAG the lag gives you redundancy and increase in productivity.  Spanning tree will not be an issue unless you have a loop.  

A ring topology for the uplinks between switches is preferred.  If you have switches A,B and in a ring, then if switch B fails, A and C will still be able to connect.

Best solution would be to have a ring topology with LAGs

No, these feature do not disable other features.

[miroslaw len]

Thank you for your answer. 

But - if I do all ports assigned to only one MAC address each- and LAG on fibre - the Spanning tree protocol wouldn;t be need, as the loops haven;t opportunity to create itselft? Am I correct?

Great :))  Iam very with finding right solution here :)

Thank you