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Am I right about my LAN design

This is my first "big" lan

I have a little more 200 nodes in my network

I plan use 5 2950G-48 EI with GigaStack connection to 3508G switch.

And I have 1 LAN segment on a distance more than 100 m with 20 nodes (2950G-24EI) . I plan to connect that segment using SX GBIC modules to the same 3508, than aggregate all "big" LAN

Is it "live" configuration?

Thank you.

Community Member

Re: Am I right about my LAN design

What type of traffic are those 200 nodes generating? From a simple design standpoint, I'd say your design is suitable. Do you already have the 3508 or are you purchasing it? If you haven't purchased yet, I would look in to using the 3550-12G instead. It has a 24Gbps switch fabric and can do layer III routing ,where the 3508cannot and only has a 10Gbps fabric.

How far is the 1 LAN segment? As long as it is under 220 m (722ft) than you are good to use the SX GBIC.

Do you want any redundancy in the network or not? If you do, I would order a second 3550-12G and have lines running from the GBIC ports on each switch to each of the 3550-12G's. If you use the 3508, I would do the same thing to create redundant paths (if the budget allows of course!!!!!!)

Good luck.


Community Member

Re: Am I right about my LAN design

Thank you Josh,

But now I have a budget , that allow me use only 3508 switch

1 LAN segment is situated on distance about 110-120 m from all other LAN

Thanks a lot againe



Re: Am I right about my LAN design


I agree with Josh, get a 3550-12G if you can. It is the better switch. List price in US Dollars is $9,995 vs. the 3508G at $4,995. For the extra cost, you get several benefits in the 3550-12G:

* two more GBIC slots (so you won't outgrow it as quickly as you will the 3508G);

* two 10/100/1000 ports (if you put 1000BASE-T GBICs in the 3508G, you will only get Gigabit Ethernet);

* 24-Gbps switching fabric gives you "wire-speed" Layer 2 full-duplex Gigabit Ethernet switching on all 12 ports (the 10-Gbps switching fabric in the 3508G only lets you run at top speed on 5 out of 8 ports at a time; I see you'll be using 6 ports to start, so this could affect you);

* "wire-speed" Layer 3 switching, or routing, of IP traffic with the Enhanced Multilayer Image software that comes standard (this accounts for $1995 of the 3550-12G's list price; and allows you to implement VLANs and route IP between them at "wire speed", something the 3508G can't do);

* multicast IP routing (the 3508G needs something "smarter" like a Layer 3 chassis switch or a router to tell it how to handle multicast traffic efficiently).

Later on, as Josh mentioned, you can budget for a second 3550-12G and enough duplicate GS or SX GBICs to provide a redundant Layer 2/Layer3 IP "core". That way, losing a Gigabit Ethernet backbone switch won't interrupt connectivity among your attached 2950G switches.

Once you have redundant "core" 3550-12G's in your network, you can use Hot Standby Router Protocol (HSRP) to give each VLAN a fault-tolerant IP default gateway address.

Basically, the 3550-12G is a switch with a future. If you go with the 3508G now, you will lock into a Layer-2-only solution. Later on, when you need Layer 3 switching or routing, you will probably end up paying more for another switch or router to get that capability, when you could have had it in your original Gig backbone switch if you had chosen the 3550-12G.

Then again, the 3508G may be fine for your network. There's a lot more that goes into network design and capacity planning than just "speeds and feeds" and features; a flat Layer 2 switched network may be just what you need. I have several customers using this same configuration, with no complaints.

Hope this helps.

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