Anyone know of a program that would detect pinout of remote end of cable?

CodeBlox

I can't find the specs for my cable modem anywhere but I suspect it's not able to properly establish a connection with my 1721 and 2950 because of MDI-X... I cannot find any doc that details what pins my modem ethernet port tx/rx on. Can anyone suggest a program that would give me this info? That way I can make a cable to the spec.

CodeBlox

No replies... I might have to just get a cable tester to get the info I need... I know the ones at work tell me what pins are in use.

MentholMoose

ethtool will show this. Most laptop NICs do auto MDI-X, so connect a laptop running a recent Linux distribution to your modem and run ethtool.

SteveO86

Not sure if the 2950 supports this but I know the 2960 series do.

Layer 1 Troubleshooting with Cisco Switches. « CCIE or Null!

CodeBlox

I'll have a look at ethtool. Thanks!

Steve - The 2950s do not support MDI-X

EV42TMAN

how do you have the router interface set up for the cable modem? i just installed an 1841 at home and i had to set it to pppoe to get it to work

CodeBlox

The only thing I configured on the router was the ip addressing (DHCP), speed, duplex, and NAT. It immediately gives a flashing orange light when plugging in. I then took the 2950 and plugged it in and got the same blinking orange light. I know that neither of these devices support mdix which is leading me to believe it's the cause. Once I get my hands on a cable tester, I can make a cable with what I believe will be the correct pinouts and see if it works.

Since my 1721 only has one Fast Ethernet interface, I'll be using router on a stick. I'll connect my switch to the modem as an access link and trunk the switch to the router giving it a DHCP acquired address on a subinterface. I have disabled STP on the link to the modem as well as CDP. I really believe the cable is the problem.