Re: dhcp snoop

From: dampened (cheechew@hotmail.com)
Date: Wed Dec 20 2006 - 23:14:24 ART


I am not using dhcp option82. Just simple dhcp snooping. I cannot access the
equipments right now.

  ----- Original Message -----
  From: Jian Gu
  To: dampened
  Cc: Cisco certification
  Sent: Thursday, December 21, 2006 4:45 AM
  Subject: Re: dhcp snoop

  Do you have ip dhcp snooping option turned-on on switch2? by defaut switch1
will drop all DHCP packets with option82 inserted, use the following command
to allow DHCP packets to go through.

"ip dhcp snooping information option allow-untrusted" Anyway, it is just my
guess, "debuging ip dhcp snooping" on both switch1 and switch2 should tell you
where theproblem is, it is a simple feature.

  On 12/20/06, dampened <cheechew@hotmail.com> wrote:
    I have topology where there are 2 switches, upstream and downstream. The
    DHCP server is on vlan 2 and client on vlan 3. Both switch are connected
by
    trunk.
    Here is the skeleton of the config.

    When ip put "ip dhcp snooping vlan 3" on switch 2, the client could not
get
    IP from DHCP. When I removed it, everything is fine, the binding is
properly
    built on switch 1. But without the snooping on switch 2, the feature
    actually is not yet configured. Whats wrong with my config?

    switch-1:

    ip dhcp snooping
    ip dhcp snooping vlan 3

    interface f0/1
    description connect to DHCP server
    switchport access vlan 2
    switchport mode access
    ip dhcp snooping trust

    interface f0/24
    description trunk to switch 2

    interface vlan 2
    ip address ...

    interface vlan 3
    ip address ...
    ip helper-address dhcp_server

    switch-2:

    ip dhcp snooping
    ip dhcp snooping vlan 3 <-----------------------------

    interface f0/1
    description connect to DHCP client
    switchport access vlan 3
    switchport mode access

    interface f0/24
    description trunk to switch 1
    ip dhcp snooping trust

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