daisy-chaining switches..

[guapo337]

posting for a friend:

does uplinking switches decrease performance? i am thinking about getting three 8 port gigabit switches and uplinking them together to create a 24 port LAN. Is there going to be any lag between the switches? They are all gigabit

 

[Lord Evermore]

As long as it's limited to just 2 or 3, there won't be any noticeable delay. If you start getting into higher numbers, you run into latency just because of the speed electricity can travel, combined with the processing that has to be done by so many switches (this is all in regards to traffic at the two extreme ends).

 

[guapo337]

Originally posted by: Lord Evermore
As long as it's limited to just 2 or 3, there won't be any noticeable delay. If you start getting into higher numbers, you run into latency just because of the speed electricity can travel, combined with the processing that has to be done by so many switches (this is all in regards to traffic at the two extreme ends).

three switches.

 

[techfuzz]

Have you thought about buying a 24 port gigabit switch instead of 3 separate switches? Too costly or what?

techfuzz

 

[MikeMike]

um it wont be 24 port, if you daisy chain them, only 20 port!!!!

MIKE

 

[Lord Evermore]

Unless they have dedicated uplink ports. And even without, uplink will only remove 3 ports, so 21 usable.

 

[techfuzz]

Originally posted by: Lord Evermore
Unless they have dedicated uplink ports. And even without, uplink will only remove 3 ports, so 21 usable.

No, he was right with 20 1 on the first and third, 2 on the second = 4 ports used

techfuzz

 

[guapo337]

Originally posted by: Lord Evermore
Unless they have dedicated uplink ports. And even without, uplink will only remove 3 ports, so 21 usable.

dedicated uplink ports. the 24 port that they have right now was over 2000 and it's having problems.. three 8s will be a LOT less and if there is no noticeable slowdown.. thats better.

 

[Lord Evermore]

Dammit. I can't count. But I have an excuse, I failed math a lot.

 

[sciencewhiz]

it's better to connect two of them into 1 then to daisy chain them

 

[Mark R]

it's better to connect two of them into 1 then to daisy chain them

Except when you have 3 switches, because connecting 2 of them into 1 is daisy chaining them.

 

[Confused]

Some switches are clever enough for you to connect into each one, so 1 is connected to 2 and 3, and then you connect 2 and 3 together also. However, some switches (probably some of the much cheaper, SOHO ones) will just end up sending data round in a loop!

If the switches you get can do that, then that will probably be quicker (to get to from one computer to another you only have to through max of 2 switches rather than 3) than connecting 1-2-3, as that would have to go through 3 switches for some things.

1-2-3 will leave you 20 usable ports

1-2 will leave you with 18 usable ports
\ /
3

Confused

 

[bocamojo]

I am no network guru... but I do have a friend who is, and I asked him your question. He said this is done all the time, and should not be a problem, as far as performance/lag are concerned. He also said there should be no significant performance advantage of using the uplink ports over daisy chaining them together using the regular ports. He said the only thing you'd have to make sure of is what kind of cable you're using. He said if you use dedicated uplink ports to connect the switches, you could use a regular straight through cable. He said if you're using regular ports on the switches to chain the switches, you need to use cross-over cables. Other than that, he said this should be no problem.

 

[sciencewhiz]

Originally posted by: Mark R

it's better to connect two of them into 1 then to daisy chain them

Except when you have 3 switches, because connecting 2 of them into 1 is daisy chaining them.

Technically, you are right. However, it is a mind set issue. If you think you are daisy chaining them, you will connect the 4th switch to one of the end switches. If you think you are connecting all switches to the middle switch, you won't do that.

Confused:
No need to connect 1 and 2 together. In both cases, you get 20 usable ports.

Remember if you are using hubs, the maximum number of hubs that a 100 baseT signal can go through is 2 (it's 4 for 10 base). Switches don't have that problem, though.

 

[Lord Evermore]

Connecting switches in a loop is not recommended. This will result in the switch learning paths to a MAC address over two ports. Spanning Tree Protocol will be used resulting in one port or the other being shut down in order to prevent traffic looping. The reason is that if the router has two paths, it has to choose one that's better and there's no way with a simple switch to do that, so STP puts in controls to determine which path should be shut down, otherwise a computer might end up receiving the same packet twice. In theory it sounds right that looping them would allow the shortest path possible, but it doesn't work, and that's why routers have route tables that allow multiple ports to be able to reach the same destination.