[c-nsp] Querry on two scenarios

[Nick Hilliard]

On 27/01/2011 11:30, jack daniels wrote:
> I have a vey basic doubt about two scenarios  -
>
> 1) SCENARIO 1
>
> VLAN X , VLAN Y , VLAN Z -----HUB---switch
>
> will vlan headers be kept intact and communication between
> a) VLAN X (SUBNET 1)  and its gateway on switch will happen
> b) VLAN Y (SUBNET 2)  and its gateway on switch will happen
> c) VLAN Z (SUBNET 3)  and its gateway on switch will happen

It might work.  Or it might not - depends on how broken the equipment is, 
and when you're talking about low-end kit, the breakage levels can be 
astonishing.

> 2) SUBNET1 , SUBNET 2 , SUBNET 3  -----HUB---switch
>
> in this case there are no vlan and I create three IP address on L3
> interface of switch one primary and other two scendory IP address.

That will "work", so long as you don't have any MAC address overlaps.  It's 
rotten bad networking practice, and will break horribly if you use 
subinterfaces / vlan interfaces with the same mac address.  It would be 
best not to design your network like this.  It will cause you long term 
problems.

Best just get rid of the hub.  BTW, a hub will be half-duplex, so your 
throughput will also be trash.

(Can you still even buy hubs?)

Nick