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Home » Forums » Forum Archives » Networking and Internet Sharing » Topic # 657

Fast Ethernet Upgrade/ Hub-Switch Install
Tornado Feb-13-01 07:36 PM
I'm having problems upgrading my network and I need your help. I have 13 computers, some with 10Base cards and some with 10/100 cards. I upgraded the old 10Mbps hub to a Linksys EFAH16W-10/100 which contains auto-sensing for port speed. Everything works fine. All 10/100 cards register as 100 coming into the hub and on each 10/100 card. Problem is the 10/100 computers are transfering at the same speed they were when I had the old 10Mbps hub connected to them. I transfered a large file from one 10/100 machine to another 10/100 machine.I thought I'd be able to see a change. Should I be able to or did I do something wrong? Another problem I'm having is I can't seem to connect the hub to a Linksys EZXS88W switch. I tryed the uplink port, that didn't work. Do I have to use a different cable type (Straight or Crossed). Please help me out, thanks!

1. RE: Fast Ethernet Upgrade/ Hub-Switch Install
lbyard Feb-14-01 07:55 PM
In response to message 0
As I understand Linksys’ documentation for your hub, it sends all packets from a port set to 10 Mhz (or BPS) to all 10 Mhz ports and from one 100 Mhz port to all 100 Mhz ports. The 10 Mhz ports can’t talk to the 100 Mhz ports and vice versa. That is, I don’t see where the hub is a hub with switch (one switch). The hub operates at half duplex instead of full duplex as a switch (http://duxcw.com/faq/network/hubsw.htm) would. A switch also sends packets to directly from the source to the destination without sending them to all of PCs as hub does (or group of PCs as this one does). A hub has the overhead associated with collision detection, etc. and a switch does not. Even if you had a switch, the transfer rate for average desktop PCs would probably be only about three times that of a 10 Mhz network, not ten times. See http://duxcw.com/digest/Reviews/Network/dlink/dhn910/dhn910-4.htm for some benchmarks. An old PC with a slow hard disk is not going to push data over a network as fast as you may think. Finally, defective or improperly wired cabling (see http://duxcw.com/digest/Howto/network/cable/cable1.htm) or the wrong kind of cable (you need CAT 5 or 5e for 100 Mhz) in a network can cause lot of network errors and excessive retransmission of packets, resulting in network congestion and overhead. Such defects, etc. will be more noticeable in a 100 Mhz network then in a 10 Mhz network. I have seen it many times. The network cards and hub may not detect a marginal network for 100 Mhz operation. Other than that, I cannot account for the lack of speed.

Excerpts from the Linksys EtherFast 10/100Auto-Sensing
Hubs User Guide:

“To uplink the hub, simply connect a regular straight-through Category 5
cable from the Auto-Sensing Hub’s Uplink port to any regular network
port on the hub, switch, or router being uplinked. The Auto-Sensing Hub
will automatically determine the optimum speed of the device being
attached to it.

Remember that while the Uplink port is in use, the port adjacent to it must
remain open, and should not be connected to any cable or node. See page 4
for important limitations when cascading hubs.”

Excerpt from the Linksys EtherFast10/100 Autosensing Workgroup Switch User Guide:

“Switches, hubs, and similar network devices are uplinked to your Switch
with straight-through Category 5 cabling. Attach the Category 5 cabling to
the uplink port of the network device that you are uplinking to the Switch,
and plug the other end of the cable into any standard RJ-45 port on your
Switch. Using the uplink port will automatically disable the port directly
next to it, since the uplink port is a shared port.”

I have forgotten the shared port limitation at least once…

I would put all of the 10 Mhz computers on your old hub, all of your 100 Mhz computers on your new hub or switch (with servers/high performance workstation on the switch), and connect both hubs to the switch.

An aside… In case you bump into the following statement in the user guide: “Computers should never be connected directly together on a network. They should always be connected to a hub,” it is an absolutely untrue statement and has no technical basis whatsoever. A crossover cable may used to connect two computers directly together. I have done it many times and it has worked perfectly well every time when the cable was made correctly. In the switch documentation they state: “In building your Fast Ethernet network, it is highly recommended to use only
straight through cabling. Use crossed over cabling as a last resort when there
are no uplink ports available.” Obviously the author doesn’t fully understand crossover cables and has probably been burned in the past by crossover cables that were not made properly. And, obviously, I rather like them--because they are much cheaper than hubs, work better, easier to transport, and don’t require electricity to operate. Larry


2. RE: Fast Ethernet Upgrade/ Hub-Switch Install
Tornado Feb-16-01 09:04 PM
In response to message 1
Thanks for your help Larry. Turns out it was a crossover cable.

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