Network cables confusion?

Shy87Shy87 ■□□□□□□□□□ Posts: 21Member ■□□□□□□□□□
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.....

Comments

  • Forsaken_GAForsaken_GA Posts: 4,024Member
    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
  • Shy87Shy87 ■□□□□□□□□□ Posts: 21Member ■□□□□□□□□□
    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

    icon_sad.gificon_sad.gificon_sad.gificon_sad.gificon_sad.gificon_sad.gif 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........icon_surprised.gif
  • AldurAldur Juniper Moderator Posts: 1,460Member
    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?
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  • Shy87Shy87 ■□□□□□□□□□ Posts: 21Member ■□□□□□□□□□
    Can you reply me.. LOL
  • hexemhexem Posts: 177Member
    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
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  • StoticStotic Posts: 248Member
    Rollover is used for console access on routers, switches...etc
  • Forsaken_GAForsaken_GA Posts: 4,024Member
    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_GAForsaken_GA Posts: 4,024Member
    Shy87 wrote: »
    icon_sad.gificon_sad.gificon_sad.gificon_sad.gificon_sad.gificon_sad.gif 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........icon_surprised.gif

    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 :)
  • AldurAldur Juniper Moderator Posts: 1,460Member
    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 :D
    "Bribe is such an ugly word. I prefer extortion. The X makes it sound cool."

    -Bender
  • Forsaken_GAForsaken_GA Posts: 4,024Member
    Aldur wrote: »
    hehe, yea I figured as much, couldn't help pointing it out though :D

    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.
  • x5150x5150 ■■□□□□□□□□ Posts: 42Member ■■□□□□□□□□
    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_omegahex_omega Posts: 183Member
    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.
  • tim100tim100 Posts: 162Member
    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)
  • DPGDPG Posts: 780Member
    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.

  • tim100tim100 Posts: 162Member
    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.
  • JockVSJockJockVSJock Posts: 1,118Member
    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)
    
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  • peanutnogginpeanutnoggin ■■■□□□□□□□ Posts: 1,096Member ■■■□□□□□□□
    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.

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  • JockVSJockJockVSJock Posts: 1,118Member
    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.
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  • stuh84stuh84 Posts: 503Member
    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.
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  • HeeroHeero Posts: 486Member
    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.
  • alan2308alan2308 CISSP, MCSA 2008, MCSA 2012, CCNA R&S, CCNA Security Ann Arbor, MIPosts: 1,854Member ■■■■■■■■□□
    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."
  • HeeroHeero Posts: 486Member
    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
  • alan2308alan2308 CISSP, MCSA 2008, MCSA 2012, CCNA R&S, CCNA Security Ann Arbor, MIPosts: 1,854Member ■■■■■■■■□□
    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. :D
  • oxzganoxzgan ■■□□□□□□□□ Posts: 44Member ■■□□□□□□□□
    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
  • stuh84stuh84 Posts: 503Member
    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.
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  • HeeroHeero Posts: 486Member
    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.
  • billyrbillyr Posts: 186Member
    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.
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  • Panzer919Panzer919 Posts: 462Member
    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.
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