0
PhillyKev

Anyone know the pairs to switch for an RJ45 local loopback?

Recommended Posts

The correct wiring (based on the normal colour coding) for a crossover cable is:

Head One

White/Orange [Pin 1]
Orange
White/Green
Blue
White/Blue
Green
White/Brown
Brown

Head 2
White/Green [Pin 1]
Green
White/Orange
Blue
White/Blue
Orange
White/Brown
Brown

Edit: So, neither were right - its 1 and 3, 2 and 6

Share this post


Link to post
Share on other sites
I don't think 4 and 5 are even used (depending on what you're doing) so I think they're lost. I thought it was like 1-3 and 2-6 for a loopback.

Quote

The correct wiring (based on the normal colour coding) for a crossover cable is:


While that is correct, he asked for a loopback. Maybe he meant x-over? In either case, he has correct answers now :D
it's like incest - you're substituting convenience for quality

Share this post


Link to post
Share on other sites
I believe the pins that are in use are 1,2,3 and 6
if you switch 1,2 with 3,6 it will give you a crossover cable.
Best to follow the color coding shown in the previous post.


1,2,3,4,5,6,7,8 on one end and 3,6,1,4,5,2,7,8 on the other. Should give you a crossover cable

Share this post


Link to post
Share on other sites
you mean a crossover cable? if so...

Standard End
Pin 1 White/Orange
Pin 2 Orange
Pin 3 White/Green
Pin 4 Blue
Pin 5 White/Blue
Pin 6 Green
Pin 7 White/Brown
Pin 8 Brown


Crossover End
Pin 1 White/Green
Pin 2 Green
Pin 3 White/Orange
Pin 4 Blue
Pin 5 White/Blue
Pin 6 Orange
Pin 7 White/Brown
Pin 8 Brown

Edit to add: bloody hell you guys type quickly!

~~~ London Skydivers ~~~

Share this post


Link to post
Share on other sites
Quote

NOT Crossover. Ethernet loopback for a cisco router to a T1.

Turns out they were both right. 1w/3 2w/6 is the standard but cisco uses their own of 1w/4 2w/5.



Nah. If you want to connect the Ethernet ports of 2 devices then you need Ethernet crossover (1/3 2/6). If you want to loop an Ethernet port you need to short 1/3 and 2/6. If you want to loop or crossover between DSU ports for a T1 you need to short or cross 1/4 2/5. It's not a Cisco thing at all. It's the cabling standards for Ethernet and T1.

I don't get the idea behind ethernet loopback for a T1. You can't connect one to the other, and looping just isolates the connection.
Owned by Remi #?

Share this post


Link to post
Share on other sites
Quote

NOT Crossover. Ethernet loopback for a cisco router to a T1.

Turns out they were both right. 1w/3 2w/6 is the standard but cisco uses their own of 1w/4 2w/5.




hmmm This doesn't make sense to me.
loopback is for testing. example recently we were having trouble with errors in our T1 circuit and so we did a loopback test on our CSU/DSU to rule out any problems with it. Ok to perform a loopback test we disconnected it from the DMark which is located two feet behind the CSU/DSU. and plugged the cable into a loopback jack which is just a small ciruit board with a rj45 jack on it.

sounds like your router has an internal CSU/DSU and you are wanting to connect it to your T1. Then you would need to use the T1 crossover cable.
At least I think that is right. Ours was setup before I started. I never needed to look that info up.

Share this post


Link to post
Share on other sites
Quote

I don't get the idea behind ethernet loopback for a T1. You can't connect one to the other, and looping just isolates the connection.



Yeah, exactly. I need to isolate it to test. You're right, not a cicso thing. it's an rj48 vs. rj45 thing. got it to work after I figured out there's a little tine loop back button on the csu module.

Share this post


Link to post
Share on other sites
hmm sounds like you have the privilege of dealing with the company providing you your T1 line. We have SBC and it was real pain in the ass trying to convince them that the problem was in their hardware and not ours. That is once we tested everything up to the DMark.

Share this post


Link to post
Share on other sites
867-5309?

Broadband Broadband who can I turn to
you give me something I can hold on to
now you think I'm like the others before
who saw you pins and switches on the wall

Broadband I got your number
I need to make you mine
Broadband don't change your number
867-5309, 867-5309, 867-5309, 867-5309

Broadband Broadband your the connection for me
you don't know me, but you make me so happy
I tried to connect you before but I lost the nerve
I tried my imagination but I was disturbed

Broadband I got your number
I need to make you mine
Broadband don't change your number
867-5309, 867-5309, 867-5309, 867-5309

I got it, I got it, I got your switches on the wall
I got it, I got it, for a good time, for a good time call

Broadband don't change your number
I need to make you work
Broadband I got your number
867-5309, 867-5309, 867-5309, 867-5309

Broadband Broadband who can I turn to (867-5309)
for the price of a jump I can always turn to you

Share this post


Link to post
Share on other sites
Guest
Quote

I have one person telling me to switch 1 witn 4 and 2 with 5, and another telling me to switch 1 w/3 and 2 w/ 4.

Anyone know for sure?



I'm seeing mention of a Cisco router in this thread - are you sure you don't mean a rollover (NOT a crossover) cable for a local ("console") connection?

If so, just reverse the connections on P2:

P1
--------------
White/Orange [Pin 1]
Orange / White
White/Green
Blue / White
White/Blue
Green / White
White/Brown
Brown / White [Pin 8]



P2
---------------
Brown /White [Pin 1]
White/Brown
Green / White
White/Blue
Blue / White
White/Green
Orange / White
White/Orange [Pin 8]

mh

.

Share this post


Link to post
Share on other sites
Heh....I wish I'd seen this thread sooner. I'd have asked if you were using Cisco and told you about that wonderful loopback button.

I still keep both an ethernet loopback plug and a T-1 plug in my tool bag just in case. AT&T is forever screwing up circuit installs and they're handy to have to jam into the smartjack on the wall so they can fix their mess.

Also, at some of the installs I've done I've seen smartjacks with a loopback button built in as well. I'll be glad when they become more commonplace.:)
Sky, Muff Bro, Rodriguez Bro, and
Bastion of Purity and Innocence!™

Share this post


Link to post
Share on other sites
Guest
Quote

Quote

(NOT a crossover)



I never said crossover. I said loopback :P

Thanks though. All straight now.



No worries. The capitalized emphasis was for those readers who might not know the difference; I figured you did.B|

mh

.
"The mouse does not know life until it is in the mouth of the cat."

Share this post


Link to post
Share on other sites
This is off-topic, but since all the geeks are here:

Someone just tried to hack my Yahoo account. I got an alert from them about multiple access attempts too close together.

Does anyone know who to contact at Yahoo to get the offender's IP address? I tried responding to the alert but I couldn't.
Owned by Remi #?

Share this post


Link to post
Share on other sites
I don't know who you would contact. But I doubt that they would give you that info. I had a laptop stolen that had ICQ set to log in at startup. I was able to get the ipaddress of the person that was using it. I gave the address to the police officer that was investigating and he was unable to get anything from AOL about the person using the laptop.

ISP's are not very friendly when it comes to divulging info about their users.

Share this post


Link to post
Share on other sites
Quote

I don't know who you would contact. But I doubt that they would give you that info. I had a laptop stolen that had ICQ set to log in at startup. I was able to get the ipaddress of the person that was using it. I gave the address to the police officer that was investigating and he was unable to get anything from AOL about the person using the laptop.

ISP's are not very friendly when it comes to divulging info about their users.



They are getting much better at working with them though. I have heard many more stories of ISPs cooperating fully with law enforcment in the last few years. AOL... who knows.
~D
Where troubles melt like lemon drops Away above the chimney tops That's where you'll find me.
Swooping is taking one last poke at the bear before escaping it's cave - davelepka

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

0