Re: Q: Hub/router/switch
On Fri, 16 Oct 1998, Timothy C. Phan wrote:
> Hi,
>
> I'd like to know what are the differences between HUB/Router/Switch?
> Thanks and please pardon my novice question!
A hub takes packets in from one port and sends them to all the other
ports. Think of the hub of a wheel and the connections to the hosts as
spokes. If a host wants to talk, it sends a packet to the hub and the hub
sends it out to all the spokes. If the host is found, it replies in the
same way.
A switch is different. Rather then send all packets to all nodes, it knows
which MAC address(es) (layer 2 switch) or which IP address(es) (layer 3
switch) are on which ports so it only sends traffic that it knows belongs
to host(s) on that port. This is more efficient because with a hub, one
machine can saturate all ports if it saturates one. With a switch, if one
port is saturated, only the destination port for that traffic is
saturated.
A router is a box with more than one interface (though it can be one
interface with several IP addresses) that decides which route a particular
packet should take. If one interface goes down, the router may be able to
find an alternative (though possibly longer) route to the destination. It
does this using things called routing protocols that allow routers to
share information about what hosts they are connected to. If the default
route to the internet, for example, becomes unavailable, it might be able
to find another router that has a default route that takes a different
path. This process is called discovery and convergence. It discovers that
something has changed and converges on a solution to the problem based on
the information it has received from other routers in the network.
George Bonser
The Linux "We're never going out of business" sale at an FTP site near you!
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