Questions about switches....

her209

No Lifer
Oct 11, 2000
56,336
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I have a 24-port 10/100Mbps switch with 1-port 1Gbps port switch.

Assume all computers have 100Mbps NICs.

Lets say 2 computers are connected on 2 of the 10/100Mbps ports. They talk to each other at 100Mbps (each way).

Now lets say that I connect 2 more computers to the hub on 2 different 10/100Mbps ports. They also start talking to each other (but not to the other two).

Do all computers still talk at 100Mbps or are all computers reduced to 50Mbps?

What about when 24 computers are connected?

What happens with a 1Gbps port and a 10/100Mbps port?

Now lets say uplink two switches together...

If I take two x-over cables and connect two 10/100 Mbps ports together, does that mean its can now handle a 200Mpbs total between the two?
 

Viper GTS

Lifer
Oct 13, 1999
38,107
433
136
The gigabit port is for an uplink connection to a faster network. A typical application would be a centrally located gigabit switch with connections running to 10/100 switches in separate rooms where a 100 mbps network would connect to the individual systems.

Switches allow communication directly from one port to another, so in your first example each device would have a full 100 mbps connection to the other.

Viper GTS
 

Scarpozzi

Lifer
Jun 13, 2000
26,389
1,778
126
Originally posted by: Viper GTS
The gigabit port is for an uplink connection to a faster network. A typical application would be a centrally located gigabit switch with connections running to 10/100 switches in separate rooms where a 100 mbps network would connect to the individual systems.

Switches allow communication directly from one port to another, so in your first example each device would have a full 100 mbps connection to the other.

Viper GTS
Having Gigabit Ethernet is nice and all, but you'd have to have a pretty heavyweight backplane to be able to utilize the uplink. Most of the time your 100mbps pipe is big enough to support 24 nodes and you don't need to worry about it.



If I take two x-over cables and connect two 10/100 Mbps ports together, does that mean its can now handle a 200Mpbs total between the two?
I'm sort of confused by this question. Your switch will probably have to be configured for multiple uplinks or clustering to do so. If you're dealing with a Cisco switch, I would assume you can get 200Mbps out of it by doing this, but I would guess configuring RIP across 2 ports like this would be kind of wierd. I haven't had to play with switches in a while... :p
 

ScottMac

Moderator<br>Networking<br>Elite member
Mar 19, 2001
5,471
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The switch would have to support aggregated links (Like Cisco's "EtherChannel / Fast EtherChannel ..."). It should also support Spanning Tree.

If you connect two switches together with multiple ports, and you don't have a loop-prevention protocol (or aggregation protocol) active (on both / all in the network), then you have a loop - your network will pop up to 100% in seconds....

If each pair of connected hosts are talking at the same time (24 hosts / 12 pairs) then you have an apparent bandwidth of 1.2G. If you have 23 100 meg ports all trying to talk out of a single 100 meg port (at the same time), then you have a 100 meg buffered hub (apparent bandwidth is 100 meg). The primary "feature" of a switch is the apparent bandwidth amplification associated with the circuit parallelism (point-to-point "circuits" each get dedicated bandwidth).

If the same 23 100 meg ports are all aimed at the Gig port (talking at the same time), then you have an apparent bandwidth of 1 Gig (oversubscribed by 300 meg).

Scarpozzi: RIP is a routing protocol, and doesn't come into play on a Layer Two switch.

FWIW

Scott