Switch Questions (switch newbie) 3

[rhpen]

We currently have about 70 connections (users, printers, etc.) on a 10-base ethernet using a bunch of hubs (various 8, 12, 16 port) linked together. We are considering switching to switches because of the theoretical increase in network speed, but I am a total switch newbie and am not sure what to get.

"layers", "stackable", "uplinks", "managed", "un-managed"

These are all things I am unfamiliar with. I've done some reading on them, but am not sure how they might apply to our situation. Here go my newbie questions.

0. I can simply replace our hubs with switches, right? I don't need to change our cabling or anything?

1. Can I just get 4 24-port un-managed 10/100 switches (for instance, d-link des-1024d), replace our hubs with them, link them together with crossover cables and be done with it? Will that give us a decent speed increase for the money (they are only about $75 each)?

2. What does "stackable" mean? I gather it does not refer to whether you can physically stack them (I assume I can physically stack "rack-mountable switches without problem)?

3. Would it be really worth it (speed-wise) to get anything more than simple, un-managed switches or would that be more like just adding bells and whistles?

4. What would you recommend?

Thank You

 

[LawnBoy]

Stackable means you can gang them together into one virtual switch. Usually that involves a special cable that plugs the two switches together, then you don't need the crossover cable.

I highly recommend managed switches. They let you look 'under the hood' at what the network as a whole is doing, or at any given port's activity. They allow you to manually force speed and duplex settings on each port.

I'm very happy with HP's Procurve switches.

 

[KiscoKid]

layers" typically refers to thw capability of the switch. This term is derviced from the OSI model (

http://www.webopedia.com/quick_ref/OSI_Layers.asp)

All switches are Layer 2 as they understand MAC addressing. More expensive switches can also understand IP (layer 3) and TCP/UDP (layer 4). These switches tend to be more expensive.

"uplinks" are just your connections from one switch to another. Typically you may have a number of 'user' switches (sometimes called access switches) and these may be uplinked to upstream switches that are sometimes capable of Layer3/4 routing.

"managed" simply means you have the ability to remotely administer the switch in question. Highly recommended and most of them are nowadays.

"unmanaged" means the polar opposite of "managed", i.e. you cannot remotely administer the switch.

1. If you are simply changing from hubs to switches, your cabling should be fine so long as you source a switch that is of course compatible with your cabling! For example, if you have a 100BaseT Fast Ethernet network, you don't want a switch with multiple 100BaseFx connections (these only support fibre and not copper connections)

I would also recommend managed switches. You'll be thankful for that when you need to troubleshoot issues because you will quickly tire of having to keep locally visiting your switch with a laptop and cable to access it.

 

[jimbopalmer]

The stacking cable is usually faster than a standards based ethernet cable, my switches stack via a 2.8 gig cable. Without stacking, you can be saturated in the crossover cable pretty easy

99% of ethernet connections move from half duplex 10 to full duplex 100 just fine, but a managed switch will allow you to see any errors that do occur.

If your network is all in one area, you can afford to be unmanaged easier than if they are on multiple floors/buildings. I had a 4 mile long LAN and needed management bad.

I would not worry about layer 3 switching with 70 users unless you have multiple buildings or multiple floors where one group of users will use a single cable to communicate with the rest of the group. About 200 users in one place would make me consider Layer 3 switching for a single floor.

I tried to remain child-like, all I acheived was childish.

 

[rhpen]

Thanks to all the responders for the fantastic, practical information. From your posts I have gathered that I want stackable and I want managed. I have zeroed in on the HP J4813A as a probable candidate (~$400 each. see end of post for specs). Let me know if you agree. Jimbo you are correct in that our network is on one floor and all in one place. The 4 switches will be sitting together in the same cabinet. Your reply did raise a few more newbie questions:

1. Are there any gotchas? I would like to just unplug our hubs, plug in these switches, turn 'em on and boom, it's working.

2. Do they typically include the cables to link the stackable switches to each other (I gather they are special cables)?

2a. The HP switch has 24 10/100 ports and 2 empty "expansion slots". I gather these are used for the uplink? I have to buy "something" to plug in to these slots to link the switches?

3. You had said that "99% of ethernet connections move from half duplex 10 to full duplex 100 just fine". Is this something that happens automatically because the switch can handle it? Or is it something I have to select on the switches? If it is something I have to select, do I then have to change the protocol settings on our servers from 802.3 to something else (mix of Netware & Windows servers)

4. How about physical cabling? Our cable is "category 3". Will that work with these switches? The HP specs didn't mention anything about cabling, but I recall other brands of switches mentioning cat 4,5,6 cabling but not cat 3.

Thanks for putting up with me some more,

HP ProCurve Switch 2524 24-Port Network Switch
Procurve switch 2524 is a low-cost, stackable, managed 24-port switch with 10/100 autosensing per port and 2 open transceiver slots for Gigabit or 100Base-FX. It offers hp Auto-MDIX on all 10/100 and 100/1000 ports and high availability features. This switch is an ideal solution for low-cost migration to 10/100 managed switching with uplinks.

Specifications

Device Type Network Switch
RJ-45 Ports 24
Expansion Slots 2
Form Factor Rack Mountable
Switch Fabric 9.6Gbps
10/100 Mbps Ports 24
RS-232 (DB-9) Ports 1

Networking Standards IEEE 802.1ad Link Aggregation Control
IEEE 802.1d Spanning Tree
IEEE 802.1p Priority Tags
IEEE 802.1q VLANs
IEEE 802.1w Rapid Spanning Tree
IEEE 802.3x Flow Control

Management CLI/Console
Web Based

 

[LawnBoy]

I've got about 30 of those 2524 switches, and I'm very satisfied with their performance and reliability. Did you know they come with a lifetime warranty? You call in a problem, they have a new one to you overnite.

(1) You can just plug them in and they'll work as unmanaged. If you want the managed features (and you do, trust me) you will need to give each switch an IP address. Then you can just browse to that switch with any web browser and access all it's capabilities.

(2) Yes, you will need to purchase a stacking module to go into one of the expansion slots.

(3)Generally, the NIC cards in the PCs will be set to autonegotiate. All ports on the 2524 default to autonegotiate as well, so you shouldn't have to do anything to achieve 100 Mb full duplex. You shouldn't have to worry about 802.3. We're also a Netware shop and I had no trouble, but we don't run IPX.

(4) Ouch. Cat3 is definitely not rated to run 100 Mb. you might get away with it for very short runs. Regardless of what equipment you buy, 100Mb requires Cat5 at minimum. Cat6 will run up to 1Gb.

That's a helluva good switch.

 

[jimbopalmer]

Darn, sad to hear about the Cat 3 cable, that is going to put you in the 1%. It will not be in spec for 100/full, even if it works. What I would do is connect to the managed switches and turn all the ports to 10HDx to begin. That should allow everyone to come back online connected to the switches instead of the hubs.

Then port by port discover which ones can actually be set to auto-10 or auto and work without glitches. (getting the servers to auto as soon as possible will show off the speed increases)

In theory, cat 3 should support auto-10 and do full duplex (quite a speed up over 10/half) but that will depend on the NICs being able to choose that combination, some will, some won't.

I would start every port at 10HDx, then try auto-10 and then auto, that way each user starts by working, then gains speed in a supervised way, much better than trying to slow down users til they work again.

The Stacking ports on a 2524 are gigabit so it will rarely be the bottleneck (the 2524s are 9.6 Gb internally)

http://www.hp.com/rnd/accessories/J4116A/accessory.htm

I tried to remain child-like, all I acheived was childish.

 

[rhpen]

Thanks to both of you again. More fantastic, practical help. You are who make tek-tips great. I guess cat 3 sounded good in 1996, but not so good today. I'll have to talk to our cable guy and see if the higher-ups want to pay to re-wire the office. If not, I'll just have to settle for whatever we can do at 10, whether it be half, full or auto (the NICs in some of our servers are probably pretty old too, so I guess I may be looking at changing a few of them). Maybe you can give me one more dose of your expertise and then I'll let you go. If you would, would you make you best guess as to the relative speed increases I make see with the various possible switch configurations which I'll list below. I imagine some changes will make larger speed adjustments than others. I would like to put some type of cost/benefit figures in my presentation. Thanks Once More...

Current system (10-base, hubs, cat3)
Cheap unmanaged switches with crossover cables
HP2524 switches (cat3, 10-base HDX)
HP2524 switches (cat3, 10-base FDX)
HP2524 switches (cat5, 100-base)

 

[jimbopalmer]

Current system (10-base, hubs, cat3)
- one device can talk but not listen at 10 meg, collisions reduce effective speed to 30% of 10 meg

Cheap unmanaged switches with crossover cables
- will try to speak 100 meg and fail if Cat 3, you will have to set each NIC to 10 meg, PC by PC, once that is done, the will allow each device to speak 10 Meg, at perhaps a 3 to 1 speed up, but may bottle neck between switches as the crossover is 100 meg

HP2524 switches (cat3, 10-base HDX)
- you can set all the ports in one webrowser, so you save 70 housecalls, same 3 to 1 speed up over hubs, but less likely to bottle neck between switches, as the stack cable is a gig.

HP2524 switches (cat3, 10-base FDX)
- totally eleminates collisions, perhaps another 2 to 1 speed up, perhaps as little as 10%

HP2524 switches (cat5, 100-base) if the traffic needs it, another 10 to one speed up, if you don't have bottlenecks then no speed up


I hope you can get the servers to auto even if the users stay auto-10

I cabled Cat 5 in 1992, it has been very good to me. I hated thinnet and thicknet.

I tried to remain child-like, all I acheived was childish.

 

[rhpen]

Very valuable information. Naturally, your reply leads me to another question.

<<I would start every port at 10HDx, then try auto-10 and then auto>>

<<I hope you can get the servers to auto even if the users stay auto-10>>

Is that to say I should try auto (at least on the servers and maybe on the workstations) even with the cat3 cable and see if it works? You seemed pretty certain that cat3 would not work at 100. What will the sign of it not working be (errors or it just won't do anything)? (auto means 100-base, I gather)

Thanks again for the help and patience,

 

[jimbopalmer]

100 will never be in spec with cat 3 cable, it may work, shorter distance have better chances.

The Autonegotiation protocol used in ethernet, called N-Way, only asks the devices what speeds they can support, never the wire. Imagine two NICs both capible of 100-full, but starting at 10-half, on poor wire. NIC 1 says "I can do 10 and 100 and Half and Full" Nic 2 says "Our common best is 100 Full, OK by you?" Nic 1 says "Sure" and they both change to 100-full which passes no packets. Both NICs realize something is wrong and change back to 10-half, which works, so they recompare their capabilities and decide 100-full is what they are both capable of. Over and Over. it is called Flapping. You can see it in the blinky lights and in the management screens. Auto-10 may help you aviod this scenario.

I tried to remain child-like, all I acheived was childish.

 

[LawnBoy]

I hated thinnet and thicknet

ARG! You said the thick word! You just ruined my whole day reminding me of THAT nightmare <shudder>.

 

[oldtimerbob]

If you are considering D-link switches, I would suggest the 3553's

Good Luck