DHCP broadcasts not going over VTP trunk.

Discussion in 'Cisco' started by formlessreflections@yahoo.com, Dec 13, 2006.

  1. Guest

    The scenerio is like this.

    Switch A --> CORE (4006) ---> Switch B

    A and B are Cisco 2524 and the core is a 4006. The 4006 is VTP server,
    A and B are vtp clients. VTP information is propagating perfectly.

    Vlan 103 has been setup on the core switch and has been asigned to
    ports on A and B.
    The user is on switch A and his resources are on switch B.

    Switch B has vlan 103 assigned to a port with a hub attached. The hub
    is another network that contains the resources the user needs. DHCP,
    Internet etc.

    Trunking has been configured between A to Core and B to Core.

    When the user plugs into vlan 103 on switch A, he does not get DHCP
    from the hub on switch B.

    If I configure another port on switch B has vlan 103 and plug into it,
    I get DHCP from the other network like I'm supposed to.

    My question is why isn't the hub's broadcasts making it over to the
    user on switch A?

    What should I look at?

    Thanks for any help you can offer.
     
    , Dec 13, 2006
    #1
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  2. Guest

    Also, the link from switch B to the Core is a gigabit Eth over fiber.
    The port is on the Router Switch Card. I learned that GMRP was enabled
    for that blade so I turned it off.



    wrote:
    > The scenerio is like this.
    >
    > Switch A --> CORE (4006) ---> Switch B
    >
    > A and B are Cisco 2524 and the core is a 4006. The 4006 is VTP server,
    > A and B are vtp clients. VTP information is propagating perfectly.
    >
    > Vlan 103 has been setup on the core switch and has been asigned to
    > ports on A and B.
    > The user is on switch A and his resources are on switch B.
    >
    > Switch B has vlan 103 assigned to a port with a hub attached. The hub
    > is another network that contains the resources the user needs. DHCP,
    > Internet etc.
    >
    > Trunking has been configured between A to Core and B to Core.
    >
    > When the user plugs into vlan 103 on switch A, he does not get DHCP
    > from the hub on switch B.
    >
    > If I configure another port on switch B has vlan 103 and plug into it,
    > I get DHCP from the other network like I'm supposed to.
    >
    > My question is why isn't the hub's broadcasts making it over to the
    > user on switch A?
    >
    > What should I look at?
    >
    > Thanks for any help you can offer.
     
    , Dec 13, 2006
    #2
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  3. response3 Guest

    One command: IP helper-address x.x.x.x , where x.x.x.x is your DHCP
    server. This needs to be done on each vlan interface, since by default
    VLAN's don't forward broadcasts between each other.

    Take a look this: http://www.routergod.com/trinity/

    -Brian


    wrote:
    > Also, the link from switch B to the Core is a gigabit Eth over fiber.
    > The port is on the Router Switch Card. I learned that GMRP was enabled
    > for that blade so I turned it off.
    >
    >
    >
    > wrote:
    > > The scenerio is like this.
    > >
    > > Switch A --> CORE (4006) ---> Switch B
    > >
    > > A and B are Cisco 2524 and the core is a 4006. The 4006 is VTP server,
    > > A and B are vtp clients. VTP information is propagating perfectly.
    > >
    > > Vlan 103 has been setup on the core switch and has been asigned to
    > > ports on A and B.
    > > The user is on switch A and his resources are on switch B.
    > >
    > > Switch B has vlan 103 assigned to a port with a hub attached. The hub
    > > is another network that contains the resources the user needs. DHCP,
    > > Internet etc.
    > >
    > > Trunking has been configured between A to Core and B to Core.
    > >
    > > When the user plugs into vlan 103 on switch A, he does not get DHCP
    > > from the hub on switch B.
    > >
    > > If I configure another port on switch B has vlan 103 and plug into it,
    > > I get DHCP from the other network like I'm supposed to.
    > >
    > > My question is why isn't the hub's broadcasts making it over to the
    > > user on switch A?
    > >
    > > What should I look at?
    > >
    > > Thanks for any help you can offer.
     
    response3, Dec 13, 2006
    #3
  4. Guest

    Actually, that's not it. I'm not concerned at all with IP at them
    moment. I just want one big broadcast domain that spans from switch A
    to Core to switch B.

    I think the problem is that one of the vtp trunks is coming in on a
    router switch module. They router blade is sort of out there on its
    own and I'm not sure how to get it to share in the VLAN fun.

    Basically the RSM has 2 gig E ports that are connected to the switch
    backplane via a bridge group.

    When I activate the vlan on any of my trunk ports STP has a shit fit
    and shuts down the port.

    I'm wondering if this is because of the bridge and what I should do
    about it. Should I etherchannel them? Turn off STP?

    Is it something else?


    response3 wrote:
    > One command: IP helper-address x.x.x.x , where x.x.x.x is your DHCP
    > server. This needs to be done on each vlan interface, since by default
    > VLAN's don't forward broadcasts between each other.
    >
    > Take a look this: http://www.routergod.com/trinity/
    >
    > -Brian
    >
    >
    > wrote:
    > > Also, the link from switch B to the Core is a gigabit Eth over fiber.
    > > The port is on the Router Switch Card. I learned that GMRP was enabled
    > > for that blade so I turned it off.
    > >
    > >
    > >
    > > wrote:
    > > > The scenerio is like this.
    > > >
    > > > Switch A --> CORE (4006) ---> Switch B
    > > >
    > > > A and B are Cisco 2524 and the core is a 4006. The 4006 is VTP server,
    > > > A and B are vtp clients. VTP information is propagating perfectly.
    > > >
    > > > Vlan 103 has been setup on the core switch and has been asigned to
    > > > ports on A and B.
    > > > The user is on switch A and his resources are on switch B.
    > > >
    > > > Switch B has vlan 103 assigned to a port with a hub attached. The hub
    > > > is another network that contains the resources the user needs. DHCP,
    > > > Internet etc.
    > > >
    > > > Trunking has been configured between A to Core and B to Core.
    > > >
    > > > When the user plugs into vlan 103 on switch A, he does not get DHCP
    > > > from the hub on switch B.
    > > >
    > > > If I configure another port on switch B has vlan 103 and plug into it,
    > > > I get DHCP from the other network like I'm supposed to.
    > > >
    > > > My question is why isn't the hub's broadcasts making it over to the
    > > > user on switch A?
    > > >
    > > > What should I look at?
    > > >
    > > > Thanks for any help you can offer.
     
    , Dec 13, 2006
    #4
  5. Guest

    wrote:
    > Actually, that's not it. I'm not concerned at all with IP at them
    > moment. I just want one big broadcast domain that spans from switch A
    > to Core to switch B.
    >
    > I think the problem is that one of the vtp trunks is coming in on a
    > router switch module. They router blade is sort of out there on its
    > own and I'm not sure how to get it to share in the VLAN fun.
    >
    > Basically the RSM has 2 gig E ports that are connected to the switch
    > backplane via a bridge group.
    >
    > When I activate the vlan on any of my trunk ports STP has a shit fit
    > and shuts down the port.
    >
    > I'm wondering if this is because of the bridge and what I should do
    > about it. Should I etherchannel them? Turn off STP?
    >
    > Is it something else?
    >
    >
    > response3 wrote:
    > > One command: IP helper-address x.x.x.x , where x.x.x.x is your DHCP
    > > server. This needs to be done on each vlan interface, since by default
    > > VLAN's don't forward broadcasts between each other.
    > >
    > > Take a look this: http://www.routergod.com/trinity/
    > >
    > > -Brian
    > >
    > >
    > > wrote:
    > > > Also, the link from switch B to the Core is a gigabit Eth over fiber.
    > > > The port is on the Router Switch Card. I learned that GMRP was enabled
    > > > for that blade so I turned it off.
    > > >
    > > >
    > > >
    > > > wrote:
    > > > > The scenerio is like this.
    > > > >
    > > > > Switch A --> CORE (4006) ---> Switch B
    > > > >
    > > > > A and B are Cisco 2524 and the core is a 4006. The 4006 is VTP server,
    > > > > A and B are vtp clients. VTP information is propagating perfectly.
    > > > >
    > > > > Vlan 103 has been setup on the core switch and has been asigned to
    > > > > ports on A and B.
    > > > > The user is on switch A and his resources are on switch B.
    > > > >
    > > > > Switch B has vlan 103 assigned to a port with a hub attached. The hub
    > > > > is another network that contains the resources the user needs. DHCP,
    > > > > Internet etc.
    > > > >
    > > > > Trunking has been configured between A to Core and B to Core.
    > > > >
    > > > > When the user plugs into vlan 103 on switch A, he does not get DHCP
    > > > > from the hub on switch B.
    > > > >
    > > > > If I configure another port on switch B has vlan 103 and plug into it,
    > > > > I get DHCP from the other network like I'm supposed to.
    > > > >
    > > > > My question is why isn't the hub's broadcasts making it over to the
    > > > > user on switch A?
    > > > >
    > > > > What should I look at?
    > > > >
    > > > > Thanks for any help you can offer.



    I think you don't have a good picture of how things are connected
    together . Don't turn off spanning tree whatever you do . The ports
    are shutting down because somehow you have created a loop in your
    network and it is protecting that . If it was as simple as your
    drawing would suggest there is no reason it should not work . I think
    somewhere something is getting missed on how it is all connected . If
    the connecting links are trunks check to make sure those trunks are
    being allowed on both sides of the trunk, on the 4006 and on the 2500's
    .. Just because the vlan is being propagated doesn't mean it is allowed
    across those links on either side , they may be manually pruned off.
     
    , Dec 15, 2006
    #5
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