+ Reply to Thread
Results 1 to 7 of 7
  1. Lambda Lambda Lambda JockVSJock's Avatar
    Join Date
    Dec 2006
    Location
    SATX
    Posts
    693

    Certifications
    M.S. in MIS/MBA, Network+, A+, Linux+ and Security+
    #1

    Default Confusion on which devices need crossover Vs straight-through cable

    So Chp 3 has a table that shows devices that use a crossover cable:

    Transmit on 1,2 and receives on 3,6
    -pc nic
    -router
    -wireless ap
    -network printer

    Transmits on 3,6 and receives on 1,2
    -hub
    -switch

    There is a "Do I Already Know This Question" that ask: "There are two devices, which require a straight-through cable?"

    The answers are:
    -pc and router
    -router and hub
    -and wireless access point

    This question is confusing me because it seems to go against the table above. Plus, on my home network, I have straight-through cable for my dumb switch and AP and they work fine.

    The only time I have used crossover cable is when I wanted to connect two pcs together via their nics.
    Reply With Quote Quote  


  2. Login/register to remove this advertisement.
  3. Senior Member alan2308's Avatar
    Join Date
    Apr 2010
    Location
    Ann Arbor, MI
    Posts
    1,632

    Certifications
    CCNA, CCNA Sec, MCITP:SA
    #2
    Quote Originally Posted by JockVSJock View Post
    So Chp 3 has a table that shows devices that use a crossover cable:

    Transmit on 1,2 and receives on 3,6
    -pc nic
    -router
    -wireless ap
    -network printer

    Transmits on 3,6 and receives on 1,2
    -hub
    -switch

    There is a "Do I Already Know This Question" that ask: "There are two devices, which require a straight-through cable?"

    The answers are:
    -pc and router
    -router and hub
    -and wireless access point

    This question is confusing me because it seems to go against the table above. Plus, on my home network, I have straight-through cable for my dumb switch and AP and they work fine.

    The only time I have used crossover cable is when I wanted to connect two pcs together via their nics.
    MDI devices (PC's, routers, AP, etc) transmit on 1&2 and receive on 3&6 and MDIX devices (switches and hubs) transmit on 3&6 and receive on 1&2. If you connect two like devices (MDI to MDI or MDIX to MDIX) you use a crossover cable. If you connect two unlike devices (MDI to MDIX) you use a straight through cable. So in your example, you should use a straight through cable when connecting a router to a switch. In the third option you left out the second device, so I can't say there.

    The reason that you can get away with using straight through cables on your home network is because a lot of newer Ethernet equipment (and almost all home gear) has what is known as "Ethernet MDI/MDIX Auto Cross" or some similar term which basically means the piece of gear auto senses what it is plugged into and adjusts which pairs it transmit and receives on automagically. Even my ancient Xterasys 802.11b home router can do this. But try connecting two Cisco 2950's together with a straight through cable. It won't work. Connect two 2960's together with the same straight through cable and it will work.
    Last edited by alan2308; 05-12-2010 at 02:45 AM.
    Reply With Quote Quote  

  4. Lambda Lambda Lambda JockVSJock's Avatar
    Join Date
    Dec 2006
    Location
    SATX
    Posts
    693

    Certifications
    M.S. in MIS/MBA, Network+, A+, Linux+ and Security+
    #3
    Thanks for the reply.

    Hmmm...mdi and mdix. Neither one of these terms are in either Cisco books.

    From CTRLink Glossary on Industrial Ethernet Terms

    mdi
    MDI
    Medium Dependent Interface. The name for the connector used to make a physical and electrical connection between a transceiver and a media segment. For example, the RJ-45-style connector is the MDI for 10BASE-T and 100BASE-TX.
    mdix
    MDI-X
    An MDI port on a hub or media converter that implements an internal crossover function. This means that a "straight-through" patch cable can be used to connect a station to this port, since the required signal crossover is performed inside the port instead of in the cable.
    Reply With Quote Quote  

  5. Senior Member alan2308's Avatar
    Join Date
    Apr 2010
    Location
    Ann Arbor, MI
    Posts
    1,632

    Certifications
    CCNA, CCNA Sec, MCITP:SA
    #4
    Quote Originally Posted by JockVSJock View Post
    Thanks for the reply.

    Hmmm...mdi and mdix. Neither one of these terms are in either Cisco books.

    From CTRLink Glossary on Industrial Ethernet Terms

    mdi


    mdix
    I don't remember if those terms are in the CCNA material or not. It's just a lot easier to use MDI than typing "device that transmits on pin 1&2 and receives on pin 3&6" over and over.
    Reply With Quote Quote  

  6. Lambda Lambda Lambda JockVSJock's Avatar
    Join Date
    Dec 2006
    Location
    SATX
    Posts
    693

    Certifications
    M.S. in MIS/MBA, Network+, A+, Linux+ and Security+
    #5
    Ok, I need to go thru and take notes on the Lammle book. Chp 1 breaks down the following for straight-Through Vs crossover cable:

    Straight-Through
    -host to switch or hub
    -router to switch or hub

    Crossover Cable
    -switch to switch
    -hub to hub
    -host to host
    -hub to switch
    -router direct to host

    So now I have another question, if your connection a crossover cable to hub to hub, it needs to go into the uplink port/interface, correct? I reason I ask is that I've never worked with any of this equipment in the enterprise.
    Reply With Quote Quote  

  7. Member
    Join Date
    Oct 2008
    Location
    FL
    Posts
    37

    Certifications
    A.S. B.S. M.S. A+, Net+, MCSE, MCSA
    #6
    Quote Originally Posted by JockVSJock View Post
    Ok, I need to go thru and take notes on the Lammle book. Chp 1 breaks down the following for straight-Through Vs crossover cable:

    Straight-Through
    -host to switch or hub
    -router to switch or hub

    Crossover Cable
    -switch to switch
    -hub to hub
    -host to host
    -hub to switch
    -router direct to host

    So now I have another question, if your connection a crossover cable to hub to hub, it needs to go into the uplink port/interface, correct? I reason I ask is that I've never worked with any of this equipment in the enterprise.
    Lammle explains it the best in my opinion, I'm reading the same book, I'm on chapter 4!
    Reply With Quote Quote  

  8. Member Project2501's Avatar
    Join Date
    Sep 2007
    Posts
    61

    Certifications
    CCNA
    #7
    L3 to L3 = cross
    L2 to L3 = straight
    L2 to L2 = cross
    Reply With Quote Quote  

+ Reply to Thread

Social Networking & Bookmarks