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  • dhcp snooping issue

    Hi,
    I activated dhcp snooping on my test envirament (C3550 Software C3550-I9Q3L2-M), Version 12.1(20)EA1a, RELEASE SOFTWARE (fc1)

    The first IP request coming from a desktop was successful. It got a valid ip. The release worked also fine.

    The new ip request and the all other failed.

    Here is the debug log (I included my comments)

    'Ipconfig /renew

    001483: *Mar 10 01:14:38: DHCP_SNOOPING: received new DHCP packet from input interface (FastEthernet0/9)
    001484: *Mar 10 01:14:38: DHCP_SNOOPING: process new DHCP packet, message type: DHCPREQUEST
    001485: *Mar 10 01:14:38: DHCP_SNOOPING_SW: Encoding opt82 in vlan-mod-port format
    001486: *Mar 10 01:14:38: DHCP_SNOOPING_SW: bridge packet send packet to port: GigabitEthernet0/1.
    001487: *Mar 10 01:14:38: DHCP_SNOOPING: received new DHCP packet from input interface (GigabitEthernet0/1)
    001488: *Mar 10 01:14:38: DHCP_SNOOPING: process new DHCP packet, message type: DHCPACK
    001489: *Mar 10 01:14:38: DHCP_SNOOPING: direct forward dhcp reply to output port: FastEthernet0/9.

    'the desktop successfully got IP


    'ipconfig /release

    001490: *Mar 10 01:15:00: DHCP_SNOOPING: received new DHCP packet from input interface (FastEthernet0/
    001491: *Mar 10 01:15:00: DHCP_SNOOPING: process new DHCP packet, message type: DHCPRELEASE
    001492: *Mar 10 01:15:00: DHCP_SNOOPING_SW: Encoding opt82 in vlan-mod-port format
    001493: *Mar 10 01:15:00: DHCP_SNOOPING_SW: bridge packet send packet to port: GigabitEthernet0/1.

    'succesfully ip release



    'ipconfig /renew

    001494: *Mar 10 01:15:05: DHCP_SNOOPING: received new DHCP packet from input interface (FastEthernet0/9)
    001495: *Mar 10 01:15:05: DHCP_SNOOPING: process new DHCP packet, message type: DHCPDISCOVER
    001496: *Mar 10 01:15:05: DHCP_SNOOPING_SW: Encoding opt82 in vlan-mod-port format
    001497: *Mar 10 01:15:05: DHCP_SNOOPING_SW: bridge packet get invalid mat entry: FFFF.FFFF.FFFF, packet is flooded to ingress VLAN: (100)
    001498: *Mar 10 01:15:09: DHCP_SNOOPING: received new DHCP packet from input interface (FastEthernet0/9)
    001499: *Mar 10 01:15:09: DHCP_SNOOPING: process new DHCP packet, message type: DHCPDISCOVER
    001500: *Mar 10 01:15:09: DHCP_SNOOPING_SW: Encoding opt82 in vlan-mod-port format
    001501: *Mar 10 01:15:09: DHCP_SNOOPING_SW: bridge packet get invalid mat entry: FFFF.FFFF.FFFF, packet is flooded to ingress VLAN

    ' no ip is provided

    Thanks for any help.
    Regards,
    Csaba Papp
    MCSA+messaging, MCSE, CCNA
    ...............................
    Remember to give credit where credit is due and leave reputation points where appropriate
    .................................

  • #2
    Re: dhcp snooping issue

    The issue was solved
    It seems that Windows 2000 / 2003 DHCP servers don't support the Option 82 encoded in dhcp packets. I had to disable it.
    Interestingly, it seems that Windows 2008 dhcp support this option.
    More details about this issue can be found here
    Regards,
    Csaba Papp
    MCSA+messaging, MCSE, CCNA
    ...............................
    Remember to give credit where credit is due and leave reputation points where appropriate
    .................................

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