dhcp problem on 2960 switches

Discussion in 'Cisco' started by SIMON WATSON, Apr 2, 2008.

  1. SIMON WATSON

    SIMON WATSON Guest

    Hi All

    I need your help

    We have a dhcp server that was connected to Cisco 2960 which in turn was
    connected to alcatel switches, all worked fine. we changed the alcatel
    switches to cisco 2960's. We now have a problem that only devices directly
    connected to the original 2960(where the dhcp server is connected to) is
    receiving IP addresses we have now 4 other 2960's onthe network but we
    cannot get a IP address when we connect to any of the ports. doing a sniffer
    trace on the working switch the DHCP four way handshake is performed,
    discovery>>offer>>request>>>ack

    On one of the other switches only the discovery is seen but no offer
    response from the dhcp server is seen therefore no ip address is received.
    the new switches only have portfast set and an ip address for vlan1 so I
    cannot understand what is stopping the dhcp traffic

    Any Ideas

    Thanks

    Simon
    SIMON WATSON, Apr 2, 2008
    #1
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  2. SIMON WATSON

    Trendkill Guest

    On Apr 2, 11:29 am, "SIMON WATSON" <> wrote:
    > Hi All
    >
    > I need your help
    >
    > We have a dhcp server that was connected to Cisco 2960 which in turn was
    > connected to alcatel switches, all worked fine. we changed the alcatel
    > switches to cisco 2960's. We now have a problem that only devices directly
    > connected to the original 2960(where the dhcp server is connected to) is
    > receiving IP addresses we have now 4 other 2960's onthe network but we
    > cannot get a IP address when we connect to any of the ports. doing a sniffer
    > trace on the working switch the DHCP four way handshake is performed,
    > discovery>>offer>>request>>>ack
    >
    > On one of the other switches only the discovery is seen but no offer
    > response from the dhcp server is seen therefore no ip address is received.
    > the new switches only have portfast set and an ip address for vlan1 so I
    > cannot understand what is stopping the dhcp traffic
    >
    > Any Ideas
    >
    > Thanks
    >
    > Simon


    You are trunking the vlan where the boxes are (logically) right? Can
    you manually set an IP on one node in the dhcp range and ping/
    traceroute to the rest of the network?
    Trendkill, Apr 2, 2008
    #2
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  3. SIMON WATSON

    Merv Guest

    on the new switches, do you see the MAC address of the DHCP server in
    the mac table ?

    Post the configs of the old switch and one of the new switches along
    with show version from both
    and show mac-address-table from both. also show ip int br
    Merv, Apr 2, 2008
    #3
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