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Can RJ45 crossover cable be used for back-to-back connection?

...and if so, would it prevent routing?

Hello, Friends

Fresh new guy, here.

Im using an RJ45 crossover cable to connect two routers together; each one connected to a switch on separate subnets. In so doing, I am having some problems and wondering if they are related to the crossover cable. Each router can ping everything except the neighboring switch. Additionally, they will not route traffic, nor do they appear to hold the static routes I enter. (Line is up, Protocol is up)

Could these issues be due to the fact that I need to use a DTE/DCE cable and set a clock rate?

Most appreciative of any assistance. This is my first routing lab.

Mark F.

MCSE / Security+ / Network+

illustration.JPG

1 ACCEPTED SOLUTION

Accepted Solutions
Hall of Fame Super Silver

Can RJ45 crossover cable be used for back-to-back connection?

Mark

Thanks for posting back to the forum to let us know that it is fixed, and what the problem was. Not having ip routing enabled is a good explanation for both symptoms (router can not ping the remote switch and router will not keep (or put) a static route in the routing table). I wish that I had thought of that in my original response.

Do not be too rough on yourself about this. Most of us (and certainly me) have equivalent (or worse) tales of what we did (or did not do) that caused problems. And on the bright side of it - the good news is that you identified and fixed the problem yourself. As I frequently tell the classes that I teach, the lessons that we learn the best are the lessons that we learned the hard way. And I believe that you will always have a tendency to check if routing is enabled on any problem that you investigate.

HTH

Rick

4 REPLIES
Hall of Fame Super Silver

Can RJ45 crossover cable be used for back-to-back connection?

Mark

There are some things in your post that puzzle me, especially the comments about whether you need DTE/DCE cable and clock rate. These would be appropriate if you were dealing with serial interfaces but your illustration is pretty clear that these are Ethernet interfaces. I am also puzzled about the statement that the routers do not seem to hold static routes that you have entered. Perhaps posting the router configurations would help us to identify the issues?

Also - am I correct in understanding that switch 3 is successful in ping to 172.16.2.1 but fails when ping to 172.16.2.20? If so then it perhaps suggests that the problem is that switch 2 does not have a correct default gateway configured. Can you confirm for us what is configured as default gateway on both switches?

HTH

Rick

New Member

Re: Can RJ45 crossover cable be used for back-to-back connection

Okay...   I'm an idiot. 

.......forgot to enable IP routing. Ungh!!   

Guess its like a car..

you can start it up, make adjustments, and have all the gears turning, but you're not gonna go anywhere if you don't put it in gear. 

Hall of Fame Super Silver

Can RJ45 crossover cable be used for back-to-back connection?

Mark

Thanks for posting back to the forum to let us know that it is fixed, and what the problem was. Not having ip routing enabled is a good explanation for both symptoms (router can not ping the remote switch and router will not keep (or put) a static route in the routing table). I wish that I had thought of that in my original response.

Do not be too rough on yourself about this. Most of us (and certainly me) have equivalent (or worse) tales of what we did (or did not do) that caused problems. And on the bright side of it - the good news is that you identified and fixed the problem yourself. As I frequently tell the classes that I teach, the lessons that we learn the best are the lessons that we learned the hard way. And I believe that you will always have a tendency to check if routing is enabled on any problem that you investigate.

HTH

Rick

Hall of Fame Super Gold

Can RJ45 crossover cable be used for back-to-back connection?

but you're not gonna go anywhere if you don't put it in gear.

Agree with Rick.  Same here.  Can't seem to understand why the router can't save it's config until a senior colleague looked at me and said, "How did you get your CCNA again?" and he showed me the configuration registry.  That moment, I had hoped that the earth would open up beneath my feet and swallow me up.  Instead the earth kept it's trap shut. 

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