Gigabit LAN not at full speed?

[CyberGenX 0]

I just set up a Gigbit network, 1 server, 1 Cisco router and 10 workstations. All the workstations have Gb NICs and I am using three 8 port LinkSys Gigabit Switching hubs.

 

Here is my problem. Although the NICs and the Switches report that everyone is connected at 1000Mbps the speed seems slower than what is was before, a 100Mbps network. What am I doing wrong?

 

 

Here is what I suspect but have not yet verified:

 

We are using CAT5 RJ45, standard 8 conductor wiring. Does Gb Networking require higher end CAT5 like CAT5E 133MHz?

 

Or I suspect the protocol, we are using TCP/IP, And NetBIOS. The TCP/IP is for internet connection, some computers have static IPs and others are DHCP off of the Cisco router. Therefore all the computer will not see each other unless we install NetBIOS or NetBEUI.

 

 

When I try to copy a file from the server to any computer I am getting less that 100Mbps. WTF!!!

[jmmijo 1]

Yeah, actually CAT6 cabling is required for Gbit copper ethernet

[sapiens74 0]

5e will do gigabit

 

 

And are these machines reporting 100mbs?

 

are they windows based machines

[jmmijo 1]

Hmm, ok, I guess I was mis-informed then. I thought the reason for having CAT6 was the extra shielding for these higher speeds, ala, the 80-wire cables for UDAM66/100/133

 

Something else I was thinking also is the Speed Selection under the device properties. Is it in the Auto position? Sometimes this has to be forced into a specific speed like 1Gbit/Full-Duplex instead.

[sapiens74 0]

The thing is, if your infrastucture is plain old cat 5, and you have to upgrade it, i would go cat 6 just to be safe.

[CyberGenX 0]

No my machines are reporting 1000Mbps, and they are all win 2000. THanks I guess we will be getting CAT6 then.

[Ron_Jeremy 0]

I installed regular CAT5 cable (non "e") between 2 Intel Gigabit NIC's & it ran just fine. So, I am not totally convinced that the "e"nhanced CAT5 cable is necessary for 1000mbs

[CyberGenX 0]

What is the distance between the two nics?

[blakerwry 0]

The difference between the catagory of cables is that cat 5 has more bandwidth than cat3, cat 5e has more than cat5, cat 6 has more than 5e, etc...

 

the more bandwidth you have, the more data it is possible to send over the line.

 

I find it likely that ron is using high quality cat5, that is probably equal to cat5e (but not certified to be cat5e) in bandwidth.

 

 

there is no other real difference in the wiring, same sheilding, same twisted pair... just better materal and stricter standards.

[nrvate 0]

correct... cat6 just has higher specs in general.

 

improper cable wiring order on the RJ45s can kill GBE thou, because of crosstalk.

 

the wiring spec for the gig-compatible cabling specifies that the green pair is flipped and spread across the blue on the connector. this is standard, but not always adhered to in all cabling assemblies. people that make thier own cables will alot of the times not split the center pairs, causing crosstalk too extreme for anything but the really short cables.

 

the wiring order i've used with great success with gbe would be:

 

white orange

orange

green

white blue

blue

white green

white brown

brown

 

the IEEE engineer I work with says the pairs are split like this to reduce crosstalk and capacitive coupling on the transmit pair of the interface.

 

wiring without the split, wo/o/wg/g/wbl/bl/wbr/br, [usually] works fine for 100mbit links because only 4 pair are used, the transmit amplitude level is lower, and the frequencies are lower.

 

when all 8 pairs are used, crosstalk is a major issue and the wiring order must be followed.

 

hopefully your NICs and switch has a media error counter. look for CRC errors, runts, and other link errors on both the NIC and the switch. if your getting link errors, your cabling is suspect, or your have a bad NIC.

 

dont forget to turn up the tcp window size now that you have such a fast connection. 0xfaf0 works nicely.

[CyberGenX 0]

Hmmm i use

 

OW

O

GW

Bl

BlW

G

BrW

Br

 

This is what they taught us to use in school.

[CyberGenX 0]

Quote:

dont forget to turn up the tcp window size now that you have such a fast connection. 0xfaf0 works nicely.

Where would I find this, I searched the registry for tcpwindowsize and tcp window size but nothing came up.

[jagancr 0]

hi

 

how to turn up tcp window size and wat is 0xfaf0 ?

 

plz suggest.

[Phalanx-Imawano 0]

Originally posted by nrvate:

Quote:

correct... cat6 just has higher specs in general.

 

improper cable wiring order on the RJ45s can kill GBE thou, because of crosstalk.

 

the wiring spec for the gig-compatible cabling specifies that the green pair is flipped and spread across the blue on the connector. this is standard, but not always adhered to in all cabling assemblies. people that make thier own cables will alot of the times not split the center pairs, causing crosstalk too extreme for anything but the really short cables.

 

the wiring order i've used with great success with gbe would be:

 

white orange

orange

green

white blue

blue

white green

white brown

brown

 

the IEEE engineer I work with says the pairs are split like this to reduce crosstalk and capacitive coupling on the transmit pair of the interface.

 

wiring without the split, wo/o/wg/g/wbl/bl/wbr/br, [usually] works fine for 100mbit links because only 4 pair are used, the transmit amplitude level is lower, and the frequencies are lower.

 

Hey man that was a really big help to me too. Though I'm not using a Gigabit LAN, I was still having problems with a 100Mbps setup involving 3 switches each connected together by LAN cables over 30ft long each (all assembled and put together by yours truely). For SEVERAL YEARS I was beating myself in the head wondering why they could not even see each other (i.e. can't ping each other, nor can any PC on one side surf the net where the router/gateway was on the other side) unless the middle switch was replaced by an old 10Mbps hub (yes hub, not switch), thus slowing down part of the network. Only after I applied that wiring layout split (wo/o/wg/g/wbl/bl/wbr/br) on the RJ-45 plugs on the long cables did I finally get the entire network running at 100Mbps without problems, and I was finally able to get rid of that old 10Mbps hub.

 

Big thanks man! You saved me the trouble of having to go out and buy a pair of 30+ft CAT5e pre-built cables which would have cost me a bundle (those beasts cost $10.00 a piece!) not to mention spare me the hours of labor having to lay them out.