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3560 trunk connections

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  • 3560 trunk connections

    Hi, guys

    I have 5 3560 (WS-C3560G-24PS) switches with IOS 12.2(25)SEE2 on all of them (I inherited this network). They are connected as a chain (each to each with MM fiber) to 4506 switch via MM fiber. All ports involved in connection configured in the same way
    interface GigabitEthernet0/27
    description 5thFlr50
    switchport trunk encapsulation dot1q
    switchport mode trunk

    Looks like works, but CDP show the strange picture
    4thFlr45#sh cdp neighbors
    4thFlr45 Gig 0/28 148 S I WS-C3560G-Gig 0/28
    4thFlr46 Gig 0/28 165 S I WS-C3560G-Gig 0/27
    4thFlr47 Gig 0/28 130 S I WS-C3560G-Gig 0/27
    5thFlr50 Gig 0/27 125 R S I WS-C4506 Gig 4/1

    This switch should see only 5thFlr50 and 4thFlr46. All other switches in the chain can see 4 switches.

    I tried to connect only two switches to each other with the cooper cable - the same behavior - each switch can see second switch and itself.
    I checked spanning tree - there no problems - no ports in blocked state. Root bridge for all VLANs is 5thFlr50 (4506).
    If I connected all switches directly to 4506 - it's ok (no any loops). So it looks like something wrong with the 3560.

    Any advices?


  • #2
    Re: 3560 trunk connections

    I played additional with other two switches in the lab. It looks like VLAN remote-span was the reason of this strange CDP behaivor.