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Testing a fibre connection



I have a Catalyst 3750 router and would like to know if this can be setup to accept communications from a storage switch which uses a fibre path to then send the signal onwards to some test equipment which uses a copper ethernet connection.

Can you keep any answers simple, I'm daft.

7 Replies 7

paolo bevilacqua
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The 3750 is a switch not a router.

What you want to do can be done, however the best approach you can take is to engage a reputable consultant for support, do not try "DIY".


So what would I be asking the consultant to do.

I do also have a 3550 router.

Leo Laohoo
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Catalyst 3550 and/or 3750 is no match for the bandwidth and the amount of data being pushed by data storage.

It'll work, but you'll gradually see a significant amount of packet output drops.

Gets even worst if your storage uses FC fibre speed instead of ethernet speed. 

Joseph W. Doherty
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Depends on what kind of fiber the storage switch is using.  Storage devices that use fiber often use a technology called Fibre Channel.  The fiber, itself, between storage devices and network devices might be the same, but the Fibre Channel interfaces are different from fiber Ethernet.  (I.e. similar problem with Ethernet and TokenRing; both use copper, but they use it differently.)

If the storage switch is using Ethernet fiber, then the two devices might be able to communicate.  However, there are multiple kinds of Ethernet fiber (both the interfaces [similar to Ethernet, FastEthernet, GigEthernet] and the fiber itself [similar to CAT3, CAT5, CAT6]).  Basically Ethernet fiber comes in different bandwidths (e.g. 100 Mbps, gig, etc.) and "distances" (SX, LX, etc.).  Unlike multi-speed copper Ethernet, Ethernet fiber needs to be an exact match on both ends of the physical link.

(This complexity is why Paolo was suggesting a consultant be retained.)

Assuming you're able to get the two devices to "talk", then you have another consideration.  Storage devices can be very bandwidth demanding, which is why Leo cautions against using a 3750.  Earlier models are not wire-speed capable across all their ports, concurrently.  Later models are, but they don't provide deep buffering for aggregate congestion (i.e. more than 1 port sending to 1 port).

The above is a long way of saying, yes it might be possible, but even if it is, there's much to understand to make it work and much to understand about how well it might work.

The intention is to use a copper link tester which verifies switch name, card and port on a fibre connection.

The fibre connection won't be transferring any data at the time of connection as I get involved when they don't work, so just require the storage switch to connect to the link tester (which uses CDP/EDP/LLDP) and tell it what switch, card and port the connection is on.

This is probably 80% "Can it be done?" and 20% "I'm too tight to buy a media converter!"

The intention is to use a copper link tester which verifies switch name, card and port on a fibre connection.

3750G/E/X can test copper links using TDR.

Leo, thanks for the above.

I've read a little about this and it seems that it would tell me if the connection exits, but not information about the other device (Switch name, Card/Port).

So I've been thinking that if I knew the WWN's for the ports in the Storage Switch then could I connect my 3750 to the fibre connections (using the correct SFP) and find out the WWN of both connections.

I could then take the reported WWN for the Storage switch port and compare that to the list of WWN's vs. Switch Name, Card/Port.

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