Cable Confusion

rc51boss

I have an issue where I can use a CAT5 cable from my PC to switch and have connectivity but not from PC to router and I have the reverse(only works with router not switch) and this is the issue with numerous cables from home made to store bought. Any thoughts?

DPG

You need a crossover cable between a router and PC.

fieldmonkey

DPG wrote: »

You need a crossover cable between a router and PC.

either that or a console cable.

rc51boss

I thought you only need xover's between like devices?

DPG

This is an exception to the rule.

Maybe someone else can chime in about the technical reason?

fieldmonkey

rc51boss wrote: »

I thought you only need xover's between like devices?

Well, the question should be asked...

Is the router configured at all for any access? I think you can only access it with a console cable or either a rollover cable.

rc51boss

I had access through the console cable but I was connecting the PC to setup a TFTP. I'm such an idiot, looking at the cables more closely I do indeed see that the ones that were working on the router were xover. Thanks for the insight.

fieldmonkey

Yea, I had to confirm it... but you can only configure the router using a console cable or a rollover cable where the pins aligned pn opposite ends, as shown below...

The devices are trying to communicate on the same end... so they are at war.

A "store bought" cable won't get you there from here.


1 to 8
2 to 7
3 to 6
4 to 5
5 to 4
6 to 3
7 to 2
1 to 8

xenodamus

"Like" devices need a crossover because they transmit and recieve on the same pins as each other. The transmit and recieve have to be "crossed" so that they can communicate.

Switches/Hubs = like devices
PCs/Routers/Access Points = like devices

johnwest43

crossover cable pinout (for 100 Mb)
1 3
2 6
3 1
4 4
5 5
6 2
7 7
8 8

billyr

Easy way to remember is:

If the devices share the same OSI layer or there is 2 layers difference = Crossover cable.

If 1 OSI layer difference = Straight through cable.

layer 3: Router
Layer 2: Switch
Layer 1: P.C, Hub, Repeater etc..

e.g.
Switch to router = 1 layer difference therefore straight through cable.
P.C to P.C = Same OSI layer therefore crossover cable.
P.C to Router = 2 layers difference therefore crossover cable.

rc51boss

billyr wrote: »

Easy way to remember is:

If the devices share the same OSI layer or there is 2 layers difference = Crossover cable.

If 1 OSI layer difference = Straight through cable.

layer 3: Router
Layer 2: Switch
Layer 1: P.C, Hub, Repeater etc..

e.g.
Switch to router = 1 layer difference therefore straight through cable.
P.C to P.C = Same OSI layer therefore crossover cable.
P.C to Router = 2 layers difference therefore crossover cable.

so where would a layer 3 switch fall into?

Bl8ckr0uter

rc51boss wrote: »

so where would a layer 3 switch fall into?

The example is overly simplified but it would be at layer 3.

DPG

knwminus wrote: »

The example is overly simplified but it would be at layer 3.

A switch is a switch even if it has some routing features.

Bl8ckr0uter

DPG wrote: »

A switch is a switch even if it has some routing features.

A layer 3 switch operates at both layer 3 and layer 2 (hence the name). The ports that are routed would be layer 3 and the ports that aren't would be layer 2, imo. But none of that really matters because in the real world everything doesn't fit nicely into the OSI model.

DPG

When it comes to cabling, a layer 3 switch should still be considered a layer 2 device.

Bl8ckr0uter

DPG wrote: »

When it comes to cabling, a layer 3 switch should still be considered a layer 2 device.

Cabling yes. Concept no. The OP simply asked where would the layer 3 switch fall into and I assumed he meant OSI layer wise. I reread his question and if he meant cabling then yes that is correct.

rc51boss

I actually meant cabling wise.