On Sun, 1 Apr 2001, Jack Flaherty wrote:
Well at lesat my ISP does.
This was the way I think it should work,

 let say: my IP is 1.3.5.7 the mac off my NIC is a1 ( for simplicity)
the IP of the gateway is 1.3.5.1, the MAC of the Cablemodem is FE

now the ISP can do arp -s 1.3.5.7 FE
that will make the CABLEMODEM the gateway for IP Address 1.3.5.7
Now the router will not make any ARPS for this ip address, therefor no one
can reply to them and hijack that address.

the ruter only ARPS when it has no entry in its ARP cache and a reply
comes in, or when the arp-refresh is hit.

unfortunally most ISP do not think the same way.

Regards
Patrick
.

> A quick question:
>
> Anybody know if certain ISPs use cable/dsl modems that have their own MACs?
> They might implement that sort of security so that overwriting a nic card's
> MAC is, well, futile. I only ask this because I noticed with my DSL modem
> there are certain procedures which are not performed by the operating system
> or the nic card (because i've switched from the original kingston to a 3com
> with no trouble or difference). These procedures performed on the dsl modem
> might consist of more than just converting the 6-wire ethernet to 2-wire (i
> think) copper dsl.
>
> I'm not an authority on the IP protocols, atm encapsulation, or anything, so
> if this comment needs to be shot down, make sure it happens.
>
> ampster
>

--
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Kind Regards
Patrick Maartense (using Pine on a Text Console)

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