helpfor option ping-check

Greg Sloop <> gregs at
Mon Jul 1 02:51:44 UTC 2013

Do you have logs? It would be a lot better if you did, and we could see
On Jun 30, 2013 6:41 PM, "Julie Xu" <J.Xu at> wrote:

> So looks like the client ID same on two PC is the problem someone manually
> setup like this? Please confirm.
> -----Original Message-----
> From: at [mailto:
> at] On Behalf Of
> A.L.M.Buxey at
> Sent: Monday, 1 July 2013 12:33 AM
> To: Users of ISC DHCP
> Subject: Re: helpfor option ping-check
> Hi,
> > There is no quick fix for this really, you need to identify each issue
> > and then diagnose and remedy.
> >
> > There is possibly a fix but it needs to be implemented on the network
> > side of things. If all of your clients are meant to be using DHCP then
> > most modern managed switches have a feature called "DHCP Snooping"
> > which will only allow the client to connect to the network if it sees
> > DHCP address allocation take place. This way it will prevent anyone
> > from manually configuring an IP address on their machine.
> usually DHCP snooping ensures that an untrusted link cannot be the source
> of DHCP address allocations. the feature that stops clients doing things
> unless they got an address via DHCP is usually IP source guard (which
> relies on their address being present int he table smaintined by the DHCP
> snooping) - along with Dynamic ARP inspection (DAI) which also uses the
> DHCP snooping tables to check if the client address matches what its ARPing
> - no more poisoning clients with fake gateway details.
> alan
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