A nice thing to have...

I am posting this because this is probably one of the most handiest devices you can own. It is called a ethernet hardware loopback plug. Their are some for CSU/DSU's and etc as well. but this one is just for ethernet.

You will need 1 spare rj-45 connector and about 3 inches of cat5e.

First off pull all the wires out of the 3 inches of cat5e and untwist the wires. Only keep the blue and orange wires.

Bend them sharply in a small U figure to fit inside the RJ-45 jack.

Short out the pin 1 to 3 with the orange wire and 2 to 6 with the blue wire. If you can use needle nose plyers to shove them in their so you dont have the wires hanging out. about .8 inches will work.

By doing this you've created an ethernet hardware lookback. These can be used to simulate a ethernet connection on a single port (single point ethernet termination) Meaning it will act as if its plugged into another device.

For an example you can plug this into f0/1 port on a Cisco 2621 and it bring the port up and you can assign an ip address and change the change timeout period and it will act as if its online, you'll be able to ping the interface, this will also work for subinterfaces as well on that physical interface so you can have 5 /24's on a f0/1 trunked and you'll be able to ping all of them to simulate a larger network then what you really have.

Any who figured this would be a great thing for you guys to know ^_^

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Comments

dtlokee

They don't work so well on interfaces that only support half duplex. An easier way to do what you're proposing is to simply use the "no keepalives" command and no shut the interface.

mgeorge

Yeah it has its ups and downs but for ccna it works great.... ccnp is a different ball game >.<

also these same plugs can be used to test loopback as well as not just on cisco equipment but many vendors.

Slowhand

Shhhhhh!!! Don't go telling people how to make their own loopback adapters, you'll run ThinkGeek out of business. Now all they'll have left will be the T-1 loopbacks.

mgeorge

lol i know how to make those as well ^_^

wait2dominate

Slowhand wrote:

Shhhhhh!!! Don't go telling people how to make their own loopback adapters, you'll run ThinkGeek out of business. Now all they'll have left will be the T-1 loopbacks.

The sad part is I've made those on my own with a small loop hanging out the end to hang off the 'network keychain' I have for work....

Always a fun thing to have, as well as the corssover adapter.

Delirious

Thanks for the how to, going to make me one when i get home.

mgeorge27 wrote:

lol i know how to make those as well ^_^

Do tell