Re: Multi-Networking in Linux - Multiple Subnets

Andy Burns <[email protected]> wrote:
> The Natural Philosopher wrote:
> 
>> Andy Burns wrote:
>>
>>> If you want multiple IP subnets on a single ethernet network, you'd be 
>>> better off using VLANs, even cheapo switches can handle that, then 
>>> your linux box with a single NIC can have VLAN sub-interfaces e.g. 
>>> eth1.1 on 192.168.0.1/24 and eth1.10 on 192.168.1.0/24
>>>
>>> If you don't want VLANs you *could* use a NIC alias so that e.g. eth1 
>>> is on 192.168.0.1/24 and the alias eth1:2 is on 192.168.1.1/24 ... but 
>>> why?
>>
>> They look the same to me.
> Sure the names of the interfaces are just one character different (a 
> colon vs a fullstop) but with VLANs, each sub-interface will keep its 
> traffic isolated, won't see broadcast/multicast traffic from the other 
> one ...

True, but keep in mind that each physical interface still sees every 
packet that flows over the wire.  If any one of them are flipped to 
promiscious mode, that physical interface can capture everything, 
whether there are vlan's or not at the logical level.

So don't rely on VLAN's in an environment where you don't know/have 
control over all the connected endpoints.