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DCE/DTE DB60 Crossover Cable bandwidth

Dzy_Az

Hello all,
Does anybody know what the maximum bandwidth/length is for Back to Back DCE/DTE DB60 Crossover Cables.

Thanks,

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Comments

wildfire

The bandwidth depends on the interface type you are using, for Serial interfaces the back to back cables run at T1 no problems (1.544Mbps) sometimes a carrier tansition can lock up the port and you simply have to remove and reinsert the cable.

Dzy_Az

Its a serial interface on a cisco 2513 router. I know the default bandwidth on serial interfaces is 1.544 Mbps but is this the maximum bandwidth for the serial port on this router? And whats the maximum length/bandwidth for v.35 db60 dce/dte cables ?

tunerX

It depends on the line driver, cable length, cable quality, and signaling type. If you increase the length of the cable then you have to reduce the data rate.

Here is a list of common specs based on maximum data rate. The data rate will be much less when the cable is at its maximum length.

v.35, RS-449, RS-422, X.21, EIA-530(422 line driver)
10mbps at 50 feet.

RS-232 and RS-423
115kbps at 50 feet.

The common 3ft HD60 crossover cables that you buy on Ebay are v.35. They are low quality but should be good at 8mbps, because they are so short. I have run one of the cables on a Fireberd (BERT) and ran tests that were good for 10^-11 without errors.

If you have high quality cables and connectors then the specs above should work consistently without any bit errors.

A 2513 should be able to provide line clocking with minimal errors at 4mbps. You may suffer bit errors but should still be good for a 10^-6 standard. If you want to go higher then you will have to introduce a different timing source such as rubidium or cesium (gps clock source at 5mhz).

Dzy_Az

Thanks for the info. I thought answering this would be a lot simpler becasue i assumed all V.35 cables had a maximum bandwidth/length limit similar to ethernet cables ie. UTP cables have a maximum bandwidth of 100Mbps at 100m etc.

The reason i wanted to know the maximum bandwidth for v.35 cables is because when configuring EIGRP you can modify the eigrp bandwidth percent based on the bandwidth of you're media.

wildfire

Done a bit of reading on this one as I couldnt find much on the net about it, was wondering myself about max lengths etc.

In my Cisco Field manual : Router config Appendix B states
V.35 Cable

Type Max Distance
2400 Baud 1250M
4800 Baud 625M
9600 Baud 312M
19200 Baud 156M
38400 Baud 78M
56000 Baud 31M
T1 15M
T2 3M

Was that the sort of thing you were after?

ps The book mentioned above is an excellent refrence and is a must for CCNP/CCIE

tunerX

Dzy_Az wrote:

Thanks for the info. I thought answering this would be a lot simpler becasue i assumed all V.35 cables had a maximum bandwidth/length limit similar to ethernet cables ie. UTP cables have a maximum bandwidth of 100Mbps at 100m etc.

The reason i wanted to know the maximum bandwidth for v.35 cables is because when configuring EIGRP you can modify the eigrp bandwidth percent based on the bandwidth of you're media.

You should actually set the bandwidth statement based on the configured clockrate of the DCE. If you set the clockrate for 2000000 then the bandwidth should be 2000

The V.35, RS-449, RS-422 standards specify the pinouts/connector ends for the cable but they all use an RS-422 line driver for voltages and electrical characteristics.

http://www.national.com/an/AN/AN-1031.pdf