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Recommended Lan Wiring for Business Buildings

Posted on 2011-10-24
Medium Priority
Last Modified: 2012-05-12
Hello Experts,

There is a 3 floor building with pre-installed Cat5 Lan Cable.

Our equipment is approximately:
30 computers (most of them with gigabit lan port)
10 network printers
2 servers with gigabit lan port (with shared folders and network applications)
1 Cisco Catalyst 3560G PoE 48 Port Switch
1 Cisco Call Manager
30 Cisco IP Phones powered over ethernet
1 Cisco Antispam
1 Cisco Firewall
2 Cisco Access points

I have heard that it is recommended (in order to keep the network traffic from computers lower than servers) connecting to the switch with Cat6 cables only Servers and Main Network Devices (such as Call Manager, Modem/Routers, NAS, Firewalls etc.)
On the other hand Computers and Misc Network devices should be connected with Cat5 Cables in order to avoid of running the Network Switch at its limits.

If so, I could keep the Cable Installation of the building as is and connect with Cat6 Cables only the Servers and Main Network devices which will be installed very close each other.

Q1) Do you agree with the above mentioned?

Q2) If not what type of cabling do you suggest to install(replace) for the building?

Kindly explain me why do you recommend one or the other solution.
Question by:mamelas
LVL 32

Accepted Solution

aleghart earned 1800 total points
ID: 37020265
Connecting with Cat5, Cat5e, or Cat6 or Cat789 cables will in no way affect how the switch is used, or the priority of the traffic.  You could connect with a couple of car battery jumper cables, and there isn't any magic that prioritizes _that_ traffic lower than Cat5.

Cat5e and Cat6 are specified to support gigabit ethernet.  I've used it on Cat5 when there was no budget allocated for cable replacement.  It was a short haul (around 50-75 feet) for connecting two test switches.  Same for patch cables...it works, but don't count on it for production use.

"Normal" desktop computers will not use the bandwidth available on a gigabit ethernet port.  Their hard drives can't spin that fast to support file transfers.  Your switch's backplane should have the capacity to handle ALL ports at full rated speed anyway.  So, the bottleneck is the inter-switch connections.

But, it looks like you only have one switch.  So, I don't see an immediate problem.

If your traffic is heavy, you can prioritize your voice traffic highest, and perhaps VLAN the servers together so they sit in their own network.  But, in such a small network, I'm not sure if that's really an issue.

You could also VLAN the phone away from the desktops and printers.  That way a flood of traffic from an errant piece of equipment would not take down the phone network.  Disable broadcast traffic between VLANs.

Who told you that cables would automatically set speeds and priorities?  That's some bad advice.
LVL 78

Expert Comment

by:slightwv (䄆 Netminder)
ID: 37020284
This is more of a theory that has 'some' merit.

CAT5 will run gigabit up to some distance.  Anything connected past that distance the NIC should autodetect there is 'some issue' running gigabit and automatically drop back to 100M.

I would check it you can throttle it at the switch and run cat6 everywhere.

Then you have maximum configuration capability and aren't relying on 'dumb luck' that your cat5 NICs will dumb themselves down.
LVL 84

Assisted Solution

by:Dave Baldwin
Dave Baldwin earned 200 total points
ID: 37020286
The wiring category of Cat5 or Cat6 does not control the speed directly.  That is determined by the ability of the equipment to send and receive on that particular length of cable.  Short lengths of Cat5 can operate as fast as Cat6.  And well installed Cat5 can be faster than poorly installed Cat6.

You might want to test the existing wiring to see if it is good enough.
LVL 20

Expert Comment

ID: 37020589
Agree with aleghart.  Give the man his points.

Author Comment

ID: 37023616
Thank you All!

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