# of SFP ports needed for campus Ethernet Ring??

[Shin Woo Paik]

Hi, I have a few simple qustions. I've looked through this site, other web sites, and books but cannot find the clear answers for these. I'd appreciate indeed if you can answer or give me any comments. Thanks.

1. I have a ring topology around the campus to connect about 30 buildings. This Ethernet Ring will connect the core switches in the MDF rooms in each building. How many strands do I need to connect the core switches? And do I need to have MAN type switches (ME series) to support REP?? Or is it ok to run just RSTP for this Ethernet Ring?

2. Also, in the simple Ethernet Ring inside the building (8 small switches and DUAL ring), do I need 4 SFP ports for this?

Thanks in advance for you help/advise.

[Leo Laohoo]

Duplicate post. 

[vmiller]

I suggested he post over here for some of the optical questions,

my bad

[Tom Randstrom · Accepted solution]

A typical ring will require 2 fibers.  Each node one the ring will require 2 optical transceivers (typically SFP, GBIC, etc.).  Each transceiver requires 2 fibers (one for transmit port and one for receive port).  The 2 optical transceivers in a ring node, one connects to the 2 ring fibers facing towards an adjacent node in the West direction and the other one faces toward an adjacent node in the East direction.

<---------------- Tx         Tx  -------------> Rx      Tx -------------> Rx      Tx ------------>

                 (W) Node A (E)          (W) Node B (E)        (W) Node C (E)

----------------> RX         Rx <------------ Tx        Rx <------------ Tx       Rx <----------

In the event of a break in a fiber break between two nodes, the nodes can reach their destination via the other direction around the ring.

To support REP, you will have to query what versions of software/hardware support this feature.

[Shin Woo Paik]

Thank you guys. I'm an IT infrastrucutre engineer. Recently, I got CCNA but still a lot to learn!!

Have a good weekend, guys~!!