Re: IP DHCP snooping

Hi Amin,

On your router if you did a "debug ip dhcp server packet" you would be
seeing

*Mar 1 00:14:26.511: DHCPD: inconsistent relay information.
*Mar 1 00:14:26.511: DHCPD: relay information option exists, but giaddr is
zero

IOS DHCP Servers don't like the DHCP Options that the Switch is now
including as part of the snooping process.

You can take to resolve this problem two ways:

On the switch include "no ip dhcp snooping information option"
Or the Router being the DHCP Server "ip dhcp relay information trust-all"

You only need one or the other to get things working. One tells the switch
to stop adding the options, the other tells the router that all the options
it receives are ok

Cheers,
Adam

On Sat, Dec 10, 2011 at 7:13 PM, amin <amin_at_axizo.com> wrote:

> Hi experts,
>
>
>
> I have a strange issue in configuring DHCP snooping
>
>
>
> Ip dhcp snooping
>
> Ip dhcop snooping vlan 1
>
>
>
> Int f0/1 ! to the PC
>
> Int f0/2 ! to the DHCP server
>
> Ip dhcp snooping trust
>
>
>
> But still it is not working, the PC is not getting ip address, here the
> debug
>
>
>
> 00:08:29: DHCP_SNOOPING: received new DHCP packet from input interface
> (FastEthernet0/2)
>
> 00:08:29: DHCP_SNOOPING: process new DHCP packet, message type:
> DHCPDISCOVER
>
> 00:08:29: DHCP_SNOOPING_SW: Encoding opt82 in vlan-mod-port format
>
> 00:08:29: DHCP_SNOOPING_SW: bridge packet get invalid mat entry:
> FFFF.FFFF.FFFF, packet is flooded to ingress VLAN: (1)
>
> 00:08:29: DHCP_SNOOPING_SW: bridge packet send packet to port:
> FastEthernet0/1.
>
> 00:08:46: DHCP_SNOOPING: received new DHCP packet from input interface
> (FastEthernet0/2)
>
>
>
> 00:08:46: DHCP_SNOOPING: process new DHCP packet, message type:
> DHCPDISCOVER
>
> 00:08:46: DHCP_SNOOPING_SW: Encoding opt82 in vlan-mod-port format
>
> 00:08:46: DHCP_SNOOPING_SW: bridge packet get invalid mat entry:
> FFFF.FFFF.FFFF, packet is flooded to ingress VLAN: (1)
>
> 00:08:46: DHCP_SNOOPING_SW: bridge packet send packet to port:
> FastEthernet0/1.
>
> 00:08:51: DHCP_SNOOPING: received new DHCP packet from input interface
> (FastEthernet0/1)
>
>
>
> 00:08:51: DHCP_SNOOPING: process new DHCP packet, message type:
> DHCPDISCOVER
>
> 00:08:51: DHCP_SNOOPING_SW: bridge packet get invalid mat entry:
> FFFF.FFFF.FFFF, packet is flooded to ingress VLAN: (1)
>
> 00:08:51: DHCP_SNOOPING_SW: bridge packet output port set is null, packet
> is
> dropped.
>
> 00:08:55: DHCP_SNOOPING: received new DHCP packet from input interface
> (FastEthernet0/1)
>
> 00:08:55: DHCP_SNOOPING: process new DHCP packet, message type:
> DHCPDISCOVER
>
>
>
> Regards,
>
> Amin
>
>
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Received on Sun Dec 11 2011 - 10:29:40 ART