Routers, switches & network speed?

We have a couple of systems with 1G network cards in our computer lab that we would like to do some testing with at their full 1G speed when talking to each other. They are sitting next to each other.

However, they are apparently hooked to some kind of switch-- and the IT department claims "our network doesn't do 1G, it's 100M. Frankly, that suggests that there's no way a 1G network card could ever talk to slower networks which I don't believe.

Don't routers typically provide for differences in speed of the uplink vs downlink side (not sure it those are the right terms, but I think one would get my drift)? In this case, the uplink is the slower side but I wouldn't think that should make any difference when the two machines are talking to each other on the same side of the router (assuming the router has a built in hub on the downlink side that can run at 1G).

The question then becomes, they call what they have a "switch" not a "router"-- but from doing some research on the term, whether it can interconnect different speed networks, I gather may depend on whether or not it's a layer 3 switch (which is synonymous with router?) or not? What kind of "switch" is capable of this sort of thing, if any? We're willing to spring for a rounter or whatever we need to get this setup and it doesn't seem like rocket science, but our IT department here apparently thinks so...

Reply to
Loading thread data ...

I think it just means you have an old switch which isn't capable of gigabit speeds. Someone else pointed-out that many gigabit ethernet cards can also drop down to 100BT and 10BT speeds - that is to say the _copper_ gigabit ones can. I don't think that gigabit over fibre ever does/did that.

I presume the systems are rather newer than the switch?

Long ago and far away, terms were somewhat less "fluid" - for example, what most home users call a "router" - those small boxes with four-ish "local" ports and a single "internet" port are typically an amalgam of a NAT, a switch or perhaps hub, and a firewall. I'm not entirely sure they actually "route" in as much as they rarely if ever connect more than one IP subnet - although that opinion may depend on whether you think that Network Address Translation is routing or not. Depending on what is happening wrt re-writing application messages to account for the NAT it could be considered an application-layer gateway.

Curmudgeons would not call anything a layer-three switch. Switching (in the context of Ethernet) is deciding on egress ports based on layer-two addressing information (ie MAC/Ethernet addresses). Routing is deciding on egress path based on layer-three addressing information (eg IPv4 or IPv6 addresses).

Dealing with different speeds is something which can happen in a switch. It can also happen in a router.

rick jones

FWIW, a hub is a multi-port repeater - all it does is "refresh" the signal coming-in on port port and "repeat it" out all the other ports. no traffic isolation.

Reply to
Rick Jones

Just connect a cable between them. You don't even need a crossover, it is usual for gigabit to figure that out itself.

All gigabit cards I know of will also do 100 or 10 Mb/s.

A router with a built in hub (repeater or switch) running at gigabit speeds would be rare. Maybe not much longer, though. Five port and eight port unmanaged gigabit switches are pretty affordable, though.

Routers are for interconnection of different networks (or subnets in some cases). A switch, previously known as a bridge, will connect different speed devices on the same network. A repeater, sometimes known as a hub (because the first hubs were repeaters) only connects hosts at one speed.

-- glen

Reply to
glen herrmannsfeldt

Rick Jones wrote: (snip)

Many use different wavelengths so it would not even be physically possible. In cases where it is, it might be that they would do it.


NAT is usually implemented as part of a router. That is, there is a whole (sub)net behind the NAT box. Some LinkSys routers have an option called Gateway/Router. I believe in Router mode it acts more like a traditional router, that is, with NAT off. NAT is convenient in reducing the need for public IP addresses, supplying a firewall (due to internal addresses not being directly reachable), and allowing a whole house to use only one ISP supplied address.

In that case, I would say that you would only have one address behind the NAT box. There are devices that do that for Appletalk, for example the AsanteTalk box allows one localtalk device to attach to an EtherTalk network in bridge mode. Otherwise, a router such as a GatorBox or FastPath allows for a separate network on each side.


I did figure out once how to make a true layer three switch. That is, packets keep their MAC address while going through the switch, by playing tricks with ARP. I don't know that anyone has ever tried to build something like that, though. It might allow the actual switch operation to be done with simpler hardware.


Single port repeaters tend not to be very useful. Hub is the term for the device used to connect up a hub and spoke network. The repeater served that function first, and tends to get associated with the word hub. As I understand it, many hubs are now switches (bridges).

-- glen

Reply to
glen herrmannsfeldt Forums website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.