Network cables confusion?

was going through cabling standards like...

devices of same time: crossover
different types: straigh through

pc to router: rollover
pc (NIC) to router: crossover

pc to switch (in console connection): Rollover

Lol actually I have been through so many examples and there are so many variations. Can someone tell me from where I can get the complete lists for different types of connections and cables.

The more examples I am doing the more I am getting confused. Can some one help in understanding this.....

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Forsaken_GA

ok, the first thing you need to do is remove the rollover cable from your vocabulary of network cabling. it's a management thing.

And you may want to revisit that PC NIC to Router type of cable.

And to really screw with your head, if any of the gear involved uses autoMDIX, then it doesn't matter whether it's a straight through or rollover hehe

Shy87

Forsaken_GA wrote: »

ok, the first thing you need to do is remove the rollover cable from your vocabulary of network cabling. it's a management thing.

And you may want to revisit that PC NIC to Router type of cable.

And to really screw with your head, if any of the gear involved uses autoMDIX, then it doesn't matter whether it's a straight through or rollover hehe

DAmmmmm.... can you be less technical lol....
I got CCENT exam so I cant remove rollover cable from my vocabulary and what is autoMDIX bla bla blaaa........

Aldur

Forsaken_GA wrote: »

if any of the gear involved uses autoMDIX, then it doesn't matter whether it's a straight through or rollover hehe

You mean straight through or crossover cable?

Shy87

Can you reply me.. LOL

hexem

Right, for the CCENT you don't need to know about MDIX. (it basically allow's you to use a straight-through cable to connect two similar devices together (such as two switches) )

Ok.

The following use cross-over
switch <-> Switch (dce to dce)
switch<-> Hub
PC <-> PC (dte to dte)
PC <-> Router (dte to dte)
Router<->Router (via ethernet)

Straight-through

Switch<->PC
Switch<->Router

Stotic

Rollover is used for console access on routers, switches...etc

Forsaken_GA

Aldur wrote: »

You mean straight through or crossover cable?

Hah, yes, I do mean crossover instead of rollover.

So much for me not being susceptible to the power of suggestion

Forsaken_GA

Shy87 wrote: »

DAmmmmm.... can you be less technical lol....
I got CCENT exam so I cant remove rollover cable from my vocabulary and what is autoMDIX bla bla blaaa........

A rollover cable is for console connections, it doesn't transfer data. Period. You connect one end to the network device, you connect one end to a serial port on something that's going to be interfacing with that hardware (usually a laptop or desktop), and that's it. You use rollover cables in order to manage the network equipment.

When it comes to data transfer, it's pretty simple. Do the devices reside on the same layer? If so, you need to a crossover cable. If they do not, you use a straight through cable.

Learning which device is properly assigned to each layer is an exercise I leave to the petitioner

Aldur

Forsaken_GA wrote: »

Hah, yes, I do mean crossover instead of rollover.

So much for me not being susceptible to the power of suggestion

hehe, yea I figured as much, couldn't help pointing it out though

Forsaken_GA

Aldur wrote: »

hehe, yea I figured as much, couldn't help pointing it out though

I agree, perfectly appropriate, IMHO, especially given that I was trying to educate. Passing along the wrong information, even something so innocuous, is not helpful for the new guy.

x5150

You should prob know whether to use a straight through or crossover by what pins the device sends and receives on.

typically NIC, router send on 1,2 and receive on 3,6

switch and hub receive on 1,2 and send on 3,6

So NIC -> switch is a straight through cable because the nic is sending on 1,2 and the wires will connect to the switch which is receiving on 1,2.

A switch to switch connection ( I think trunk connection ) will need a crossover cable because you can't send on 3,6 which connects to 3,6 on the other switch which is also trying to send through that same wire. You need to cross the wires of a regular straight through cable so that pins 1,2 will connect to 3,6.

hex_omega

Correct me if I'm wrong, but aren't all gigabit devices autoMDIX? It which case you could use either a straight through or crossover, and the port will adjust accordingly.

tim100

Just think of AutoMDIX as "auto crossover" for pins 1,2,3,6 where transmit/receive will internally cross on the port itself.

MDI - Medium Dependent Interface

MDIX - Medium Dependent Interface Crossover (transmit/receive internally cross)

DPG

hex_omega wrote: »

Correct me if I'm wrong, but aren't all gigabit devices autoMDIX? It which case you could use either a straight through or crossover, and the port will adjust accordingly.

Nope, I have needed to make a gigabit cross-over cable a few times before.

tim100

hex_omega wrote: »

Correct me if I'm wrong, but aren't all gigabit devices autoMDIX? It which case you could use either a straight through or crossover, and the port will adjust accordingly.

No. A Catalyst 3550 for example doesn't support AutoMDIX.

JockVSJock

Forsaken_GA wrote: »

A rollover cable is for console connections, it doesn't transfer data. Period. You connect one end to the network device, you connect one end to a serial port on something that's going to be interfacing with that hardware (usually a laptop or desktop), and that's it. You use rollover cables in order to manage the network equipment.

When it comes to data transfer, it's pretty simple. Do the devices reside on the same layer? If so, you need to a crossover cable. If they do not, you use a straight through cable.

Ok, this answers my questions on why I'm not able to ping a Cisco 2900 Switch from my computer.

I'm connected directly from a rollover cable and was able to assign an ip address to the vlan (yup, I'm new at this).

interface VLAN1
 ip address 192.168.1.200 255.255.255.0
 no ip directed-broadcast
 no ip route-cache

However I can't ping back to my linux computer:

C2900#ping 192.168.1.100

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.1.100, timeout is 2 seconds:
.....
Success rate is 0 percent (0/5)

peanutnoggin

JockVSJock wrote: »

Ok, this answers my questions on why I'm not able to ping a Cisco 2900 Switch from my computer.

I'm connected directly from a rollover cable and was able to assign an ip address to the vlan (yup, I'm new at this).

No worries... everyone has to start somewhere! You should bookmark this post and look back at it a year from now. It'll put into perspective how much you've learned!!! You'll be amazed! Good luck with your future endeavors.

-Peanut

JockVSJock

Forsaken_GA wrote: »

ok, the first thing you need to do is remove the rollover cable from your vocabulary of network cabling. it's a management thing.

Forsaken_GA, what is the best way then to refer to a rollover cable?

Both Cisco books by Lammle and Odom refer to this cable with this name.

stuh84

JockVSJock wrote: »

Forsaken_GA, what is the best way then to refer to a rollover cable?

Both Cisco books by Lammle and Odom refer to this cable with this name.

It's not about calling it something different, its about not viewing it as integral to a running network. It is integral to managing one and creating one, but it isn't required for packets to flow between destinations.

Heero

JockVSJock wrote: »

Forsaken_GA, what is the best way then to refer to a rollover cable?

Both Cisco books by Lammle and Odom refer to this cable with this name.

Basically, once your network is up and running the rollover cables wont be doing anything but sitting there for future use if you need console access to configure a router.

as far as crossover and straight-through, think of it this way. There are 8 pins on an ethernet cable. PCs transmit on pin 1 and 2, and recieve on 3 and 6. This means that what gets sent on 1 and 2 needs to arrive on 3 and 6. A crossover cable does this for you, crossing the pins so that 1 and 2 on one side are connected to 3 and 6 on the other, and vice versa.

A straighthrough cable is the same on both ends, meaning 1 and 2 are the same on both. Seems like it would have no use, but the thing is that hubs and switches both perform the crossover internally, meaning that you want straight-through cables when connecting to a swtich or a hub because they do the crossover for you.

mdi/mdix basically means that the NIC can dynamically figure out if what pins it is recieving data on and alter its operation to accomodate, meaning you can use crossover or straightthrough with no consequence if your NIC supports it.

alan2308

Heero wrote: »

mdi/mdix basically means that the NIC can dynamically figure out if what pins it is recieving data on and alter its operation to accomodate, meaning you can use crossover or straightthrough with no consequence if your NIC supports it.

Not exactly.

MDI and MDI-X are two standards describing which pairs that a device will transmit and receive on. What you are referring to is "auto MDIX."

Heero

alan2308 wrote: »

Not exactly.

MDI and MDI-X are two standards describing which pairs that a device will transmit and receive on. What you are referring to is "auto MDIX."

close enough i guess

alan2308

Heero wrote: »

close enough i guess

Close enough only works in horseshoes and hand grenades. I'm sure I speak for everyone here when I say we'd rather know for sure and actually pass the exam.

oxzgan

hexem wrote: »

Right, for the CCENT you don't need to know about MDIX. (it basically allow's you to use a straight-through cable to connect two similar devices together (such as two switches) )

Ok.

The following use cross-over
switch <-> Switch (dce to dce)
switch<-> Hub
PC <-> PC (dte to dte)
PC <-> Router (dte to dte)
Router<->Router (via ethernet)

Straight-through

Switch<->PC
Switch<->Router

Straightthrough can also be used for connecting 2 switches
conditions one side must be connected with uplink ports.Rember only one side

stuh84

oxzgan wrote: »

Straightthrough can also be used for connecting 2 switches
conditions one side must be connected with uplink ports.Rember only one side

This has nothing to do with one being an uplink. The uplink port would need some form of AutoMDIX to work like this. Given most uplinks are gigabit, that would explain why it works.

Heero

With ethernet, you transmit on pins 1&2. This needs to be received on pins 3&6. A crossover cable is a cable that physically swaps the individual wires and performs a crossover so that pins 1&2 connect to pins 3&6 on the other end.

Switches and hubs do this crossover internally. Routers and hosts do not.

The crossover needs to be done at some point, whether by the wire or a switch or a hub.

billyr

The easiest way to remember which cable to use, is to use the OSI layers.

e.g

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

If the devices you are connecting share the same layer, e.g Router to Router (L3 - L3) or there is 2 layers difference, e.g P.C - Router then you use a crossover.
If there is only 1 layer between the devices, e.g Switch - Router then its a straight though cable.

e.g P.C - Router: 2 layers = Cross over.
Switch - Switch: Same Layer = Cross over.
P.C - Switch: 1 layer = Straight through.

sthompson86

I found and added this picture to my collection of study sheets

https://learningnetwork.cisco.com/servlet/JiveServlet/showImage/2-81041-14675/crossed-or-not-crossed.jpg

Panzer919

JockVSJock wrote: »
Ok, this answers my questions on why I'm not able to ping a Cisco 2900 Switch from my computer.

I'm connected directly from a rollover cable and was able to assign an ip address to the vlan (yup, I'm new at this).
interface VLAN1
 ip address 192.168.1.200 255.255.255.0
 no ip directed-broadcast
 no ip route-cache
However I can't ping back to my linux computer:
C2900#ping 192.168.1.100

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.1.100, timeout is 2 seconds:
.....
Success rate is 0 percent (0/5)

That is correct, a console cable (Rollover) is only used to transmit keystrokes and receive output information (so you can see what your typing, status and debug messages etc.).

You would need to hook your computer into the switch and assign it an IP in the same subnet as your vlan. I was always taught when troubleshooting start at layer 1 and work your way up, its a good habit to get into.