Sometimes it amazes me
that routers work at Layer 3
when switches very will could do
the job at simply Layer 2
But switches work at Layer 3
Oh, how confusing this can be
When bridges work at Layer 2
and routers can be bridges too!
And when you hope there'd be no more
you find a switch at Layer 4
So Layer 4, and 2, and 3
imply OSI conformity
But these are simply building blocks
in what we'll call an "Interconnect Box".