how do I set the MAC address in POSTROUTING?

[sean]

Pascal Hambourg wrote:
> Hello,
> 
> sean a écrit :
>> Daniel Musketa wrote:
>>>
>>> AFAIK MAC addresses are used in ethernet to address ethernet frames. 
>>> On ip routed ppp0 no ethernet frames arrive.
>>
>> OK. If that's the case, then the --mac-source target would only work 
>> on a LAN, not over the ethernet.
> 
> I guess you mean over the *in*ternet. Ethernet is a LAN technology.
> 
>> This would mean thatthe --mac-sourse target has very limited use - 
>> only on local LANs.
> 
> Indeed, the scope of a MAC address is link local, limited to the LAN.
> 
>> But there is still a place for a MAC address.
> 
> On an IP/PPP link ? No way. A PPP interface has no MAC address, it is 
> useless. There is a place only in the lines that the LOG target prints 
> because they have a fixed format.
> 
>> How can I  put one in the packet on the client side? This would allow 
>> me to use it over the internet.
> 
> You cannot use MAC addresses over an IP/PPP link. You cannot rely on MAC 
> addresses over the internet either because this is layer 2 information 
> that is not routed by definition.
> 
> 

But I don't want to use the MAC address to route anything. I 
just want to stick it in the packet so _iptables_ will see it.

The internet routers just look at the ip address, so I 
wouldn't think they'd strip out the MAC address, do they?

If not, then if the client inserts a MAC address, couldn't 
iptables use it when it finally arrives.

sean