Newbie question: How many switches can I install 100m apart?

I have little experience in expanding networks. Wondering whether if I can expand an existing 100Mbps network comprising of two fast Ethernet switches placed about 60m apart. What I need to do is connect a couple of workstations residing in another building which is about 90m from one of the existing switches. Is it possible to run a cat6 from the switch to the new building and install another switch there?

TIA

Reply to
mike
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If you look at groups.google.com, you can read many good answers to this question.

Basically: it is possible, but far from advisable.

Reply to
Gerard Bok

802.1d says (or did at one time) that the limit is 7 hops.

You are proposing 3 hops so are well within those limits.

So it's Ok. (and advisable too).

There seems to be the idea that this 7 hop limit may not be such an issue with modern equipment however it's not what the standard says.

The 7 hop limit was expected to include thinks like 64k WAN links and CPUs are now orders of magnitude faster.

If you are running cable put in more than one.

Reply to
Bod43

I'm far to lasy to read 802.1d, but I recall a 3-4-5 rule :-)

Read back in this newsgroup: from an ethernet point of view, there is no problem at all.

From a 'cabling', 'safety' and 'regulatory' point of view it is not advisable --or even prohibited-- to run such a length of copper between 2 buildings.

Reply to
Gerard Bok

mike wrote in part:

Sure, this will work for a while until you get a nearby lighting strike. Then one or more stiches & possibly NICs will get fried.

The correct way to do interbuilding is with fiber.

-- Robert

Reply to
Robert Redelmeier

It is basically not that much a hard limit but a recommendation, so that the STP topology information cached in the switches does not time out in an unreasonably short time (or even before the STP BPDU actually would have arrived). Aside from that, it would actually require to have the 802.1d Spanning Tree implemented *and* activated to fall under this guideline. When using RSTP (which is far more common now) or when you know what you are doing (and are able to set your own max_age), you will not be affected.

It actually does not have any relation to round trip times of your links or the processing power of your switches. The trouble is, that the "message age" of a BPDU is increased by one at each bridge. And the sum value of the message age is subtracted from the max_age (which will be 20 seconds in most defaults) when building topology information.

Reply to
Denis Jedig

There is no such rule in any of the standards. It used to be a "safe" guideline for nowdays rather antiquated equipment to stay within the boundaries of maximum propagation delays prescribed by the Ethernet standards. However, as switched networks separate collision domains, it absolutely does not apply here.

There is nothing in the standards that restrains you from having a 90m link. Actually, you might have a working unrepeated 150m copper link operating over standard ethernet equipment, if you get it right. Anything longer than 90m however would be outside of the structured cabling standards defined in the ISO/IEC IS 11801 or TIA/EIA 568 respectively.

While it is true that interbuilding links might (and often enough will) introduce problems with equalizing current between the two linked points, such links may as well work stable for years, even despite of lightning strikes.

Reply to
Denis Jedig

Quite

You just need switches with fiber uplinks.

But as its "just a couple of pc's" you might find a wireless bridge cheaper than having to get fiber pulled - esp if you don't own the land between.

Reply to
developers

How about two media converters at both ends instead of switches with fiber uplinks?

Reply to
mike

as long as there is some glass between the 2 buildings you should be fine.

it may be cheaper to use copper and accept the risk that equipment gets damaged?

Or use DSL modems if you have phone quality copper between the 2? Again - may still get damaged.

Reply to
stephen

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