Cascading switches

[argint]

Hi All, Firstly, thanks again for a great forum site, great articles, great, er, everything ;-) Its one of those site finds that still excites!!!

My background is software development so Im relatively new to the network side of things. However, getting to the point, as discussed above.....
I also want to run several "desktop" switches from a master switch. I wondered how that might effect each "port" on the master switch The average user is an Office (MS office) user, so its not heavy traffic, maybe loaded by patch tuesday, big document scans etc, all hosted services like sharepoint, email etc... (I have these noob images of a cat5e cable with too much "stuff" being squirted down it!!!)

So - in summary, mounting a switch under each group of four/six nodes, and feeding that desktop switch from the master switch (all gigabit) wont cause any problems?

Is this a common scenario, or do people more often have one wire per node? One wire per node isnt really practical for us, dues to dek layouts etc...not impossible, but not really what we would like.

BTW, is there a good intro book on designing networks like this for technically minded newcomers? Not too basic, not too heavy read?

Many thanks in advance.....

Argint

 

[thiggins]

Cascaded switches are very commonly used for just the reasons you cite. The only way to know if the uplinks are going to get saturated is to do traffic analysis. Managed or smart switches can help with this, since they can provide traffic stats. Dumb/unmanages switches can't.

The other advantage of managed switches is that you can use link aggregation to group ports to provide increase uplink bandwidth--assuming that you have multiple cables between the switches!

I don't have any good book recommendations, sorry.

 

[YeOldeStonecat]

Quite common.....depending on how your office/building is layed out, if you need to cascade switches, try to keep it like a pyramid structure, and try to keep the amount of "hops" to a minimum, evenly distributed.

In an ideal world you want a single large switch, into which you plug in your server(s), uplink your router, and uplink all of your nodes from a patch panel. But that's not always possible.

More common is to have a "head switch"...into which you plug your server(s), uplink your router...and then have home run uplinks leading to switches in other rooms or on other floors of your building....into which you'll plug your workstations 'n other network devices. So your workstations will each have 2x hops to the server, and 3 hops to the internet.

What you want to avoid is having switches cascaded off of other switches cascaded off of yet other switches...etc etc.

A recent job that I redid...this non-profit organization for adult continuing educations resources, they had their office in a 3x story big old brick building that I believe was an old town hall. The internet came into the building in the basement, which was finished..and full of classrooms. Now picture this...they had 11x switches total, each switch was cascaded to another one..and they zig zagged from that bottom floor all the way to the top floor. Something like 50-60 computers total. And these switches were mostly little 5 and 8 port SOHO/home grade switches....a few were even just hubs. This place was heavy internet users. Computers on the top floor....hanging off of that last switch...were going through 11x busy stuffed saturated switches to get to the router and then to the internet (12 hops total). Those computers on the top floor were getting internet performance worse than dial up. While computers on in the basement were getting pretty much full speed on the internet. Making matters worse....all cables were run by hand...taped along the floor, carpet, stapled to baseboards 'n molding around doors, ceiling. Staples were done by someone who didn't know not to pinch ethernet, cables on floor being stepped on and rolled over with chairs.

It was the ultimate picture perfect example of "How NOT to do your network".

We redid this place, they got a grant for a server and IT infrastructure...so put in a Proliant DL360 with Small Business Server, small cabinet, nice HP ProCurve in that cabinet and a patch panel for the basement level and the first floor. All PCs on those floors direct shot to the patch panel and thus the switch. Server into the switch, RV0 router into the switch for their Motorola Canopy internet (5 meg pipe). Second and Third floor...HP ProCurve in a maintenance closet...with a home run going down to the patch panel in the basement..right into the big switch. All PCs on second and third floor had runs going to the ProCurve switch on their floor. So no computer has more than 2 hops to the server, and a 3rd to the internet. Doing online speed tests from computers on the top floor now hit pretty much full internet speed.