Switch 3850

[mals5479]

Hello there,

Little bit about my self, I am coming from the industrial side and very minimal experience with cisco products. Most of the produces I deal with are Siemens and Moxa. 

Do the Cisco switches 3850 with family protocols IEE 802 protocols support ring typologies?  

Thanks this information would be vary helpful.  

[Philip D'Ath]

You will be interested in REP (Resilient Ethernet Protocol).  Here is an overview of REP.  Search for the word "ring".  A ring is just one of the topologies supported.

http://www.cisco.com/c/en/us/support/docs/lan-switching/ethernet/116384-technote-rep-00.html

You need to be running quite new software on the 3850.  These are the instructions to configure it.

http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3850/software/release/16-1/configuration_guide/b_161_consolidated_3850_cg/b_161_consolidated_3850_cg_chapter_010001011.pdf

[Philip D'Ath]

You can also use the much simpler rapid spanning tree.
http://www.cisco.com/c/en/us/support/docs/lan-switching/spanning-tree-protocol/24062-146.html

I would tend to use rapid spanning tree for most occasions.  REP is much more complicated to setup, so you really have to want its benefits.

[mals5479]

What is the convergence time of 3850 to enables STP Root Ports and STP Designated Ports to change from the blocking to forwarding port state?   .

How many hops can the 3850 have with the RSTP?

Thanks for your time

[Philip D'Ath]

With RSTP the convergence time is usually sub-second.

I found this Cisco test paper where they did a 16 node ring.

http://www.cisco.com/c/en/us/td/docs/solutions/Verticals/EttF/EttFDIG/ApA_EttF.html

[mals5479]

Ring topology is very simply: it composed of 7 branching non Cisco switches (Siemens scalance X308), which connect the PLCs to ring.  Information transfer is 800MB per cycle.

The reason we chose Cisco 3850 was because they had the option of 24 SFP, 4 RJ45 ports switch/Router ability.  The 3850's would  serve as pair of redundant switch that close the ring at to extremes and rout  data to an exiting Ethernet IP network.  I agree with you that the REP, would be to much for this. 

Would the REP support other non-Cisco switches with RSTP protocols connected to the ring?

Is this REP, just download to the switch? How difficult is it to commission? 

[Philip D'Ath]

REP only works with Cisco switches.  You normally use REP instead of RSTP.

REP is not so much downloaded to the switch; if is just something you configure up.

Cisco has a very good implementation of RSTP.  Some other vendors not so much.  If you are going to mix vendors you would need to test it.  I don't know how good the Siemens implementation is (or if it even supports RSTP).

Another simpler safer method might be to form a smaller ring of Cisco 3850's, and then hang the Siemens off that, not in a ring.