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I'm a newbie in networking. I have this question in mind lately. I bought a gigabit switch and tried to cascade it with my existing fast ethernet router and switch. I have 1 server which is connected directly to the router and 10 workstations in which 5 workstations are connected to the fast ethernet switch and the other 5 are connected to my new gigabit switch. I noticed that all of my workstations became slow except for the server. My router directly connects to the fast ethernet switch and that switch directly connects to the gigabit switch so that all workstations may have access to the internet. I've tried to look for solutions in the web but I can't find one that can answer my query. Is it possible to cascade fast ethernet router and switch to a gigabit switch without changing everything into gigabit devices?

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Can you give some numbers on what kind of speeds you are seeing on the workstations? –  cmorse Jan 3 '12 at 6:01
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Explain slow? What is slow. How slow? –  t1nt1n Jan 3 '12 at 6:17
    
Are they all managed switch? All unmananged? Some of each? (And slow to access the server? Each other? The Internet?) –  David Schwartz Jan 3 '12 at 7:40

3 Answers 3

Are the devices managed/smart or dumb/basic?

If they are managed/smart - see if you can enable snmp to see how much traffic is flowing - a trial of orion network performance monitor will help you quickly look at historical traffic.

If not smart switches you can try copying a file from your server with a client plugged into various points of your network although beware of network traffic, and whether your server is capable of consistently delivering wire speed and whether it has any other load when testing. Windows task manager will give you a basic traffic graph.

The gig switches should work fine with the rest of the megabit network (although obviously if the uplink is 100Mb, don't expect any more throughput).

However I do remember spending some time diagnosing a flaw with some Cisco switches. That situation was slightly inversed to yours - we had servers plugged into a gig core switch which then cascaded to megabit access switches.

In the end it was deduced the access switches didn't work properly with some 100/1000 NICs and would only deliver about 20Mb throughput - surprisingly the same NICs when plugged into the gig core switch had the same issue if manually locked to 100Mb, but the core switch was fine with all the server gig NICs.

Edit: Check the uplinks are locked at both ends to 100Mb full duplex - duplex mismatch can cause fun!

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Is it possible to cascade fast ethernet router and switch to a gigabit switch without changing everything into gigabit devices?

Yes, and it will work exactly as you might expect. The devices connected to the gigabit switch will operate at 1Gb (assuming they have GbE NICs). The devices connected to the 100Mb Router will operate at 100Mb (again assuming they're capable). Communication between devices will operate at the lowest common denominator of the line of communication.

I noticed that all of my workstations became slow except for the server.

I think the "slowness" is placebo; it's all in your head; nothing is actually slower.

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Actually this is true in only 99% of the cases - but imho archie is in the 1% where there is a problem... But without further information it's only a guess - duplex/speed missmatches due to a failed autonegitiation, too small mac-tables (per port), ... there is a variety of problems to encounter...

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