Routers v. Switches

[hot_ice]

Routers and Switches...is there a difference. Well, yes there is. I was (still kinda am) confused about the whole concept of the two and didn't really know what the benefits of each one were versus the other. So I took some time-out to look up some info and noted it down and here it is:


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*Routers:
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- Basically a hardware device (can be software) that is used to forward data across a network.
- Routers forward the data depending on the network address, rather then the hardware address (known as the MAC address). So for TCP/IP networks, it would forward on the IP address.
- Routers seperate each LAN into seperate subnets, each having a different third 'octet' - ie 192.168.1.1 and 192.168.2.1 - they send data across these subnets.
- Basically, if the destination host (for the incoming packet) is on one of the router's subnets, it send it to the host. If the destination host isn't on it's subnet, the router sends the packet to a next-hop-router - it may have to choose among several (takes quickest route). Then that next router does the same...and so on, until the destination host is reached.
- Initially, they need to be configured, but ones that is done, they can 'learn' the paths of the network - even when new routers are added (they maintain a table which determines the best path for data to travel)
- Provide bandwidth control, keeping data out of subnets if it doesn't belong there.
- Routers are more expensive then switches, and if you want something to split your broadband connection or whatever between a few computers, it would be more feasible to get a switch. Switches are cheaper and you won't see much improvement with a router at all.

*Switches:
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- Switches send data across the same subnet.
- Can process two or more pairs of communicating ports simultaneously.
- They operate on the data link layer (layer 2) in the OSI architecture (sometimes layer 3 - network layer).
- Switches are good for heavily loaded networks to control data flow and increase performance and speed.
- Switches are replacing more routers in networks, as they are cheaper than routers. However, routers are still needed at the 'edge' of the network, to communicate with the 'outside world' (other networks).

In short:
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*Routers: Slower, Expensive, benefits of alernative routing^
*Switches: Faster, Cheaper, NO benefits of alternative routing^

^ alternative routing is the ability to determine a different path to take for data to travel to the destination host when the best possible path to take is down or busy.


My resources:
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http://whatis.techtarget.com/
http://www.webopedia.com/

and ofcourse google.com was the most useful tools, which helped me find info from these pages:
http://www.practicallynetworked.com/...idge_types.htm
http://www.asante.com/support/router...hardwared.html
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I'm sure most of you with your network expertise know this and can help out if I missed something. But hopefully it's a quick and easy guide for newbies.

Greg

[souleman]

You forgot one very important thing. Most routers can also perform NAT (Network Address Translation) where as switches can not. That way, if you have a broadband connection, you can assign 192.168.* addresses to your computers, but the router will still have whatever address your broadband company provided. Also, routers will not transmit "private" addresses. If you have a network of 192.168 computers connected, with a switch connecting to another network, the message may leave your internal network. If they are seperated by a router, the message will stay in your subnet.

Most of the time when you by a broadband router (like linksys cable modems) it has a 4 port switch, with a built in router. That way you can connect 4 computers in your local subnet, and still connect to the outside world. But messages for your other computers stay in your subnet. They only leave if they are addressed to an outside computer.

[SoggyBottom]

In addidtion to NATing, you can also have access lists on routers which polices traffic in a similiar way to a firewall.

If anyone wants to know more about routers ie. How to configure the interfaces, adding routes, creating access lists, passwords etc.. You can download a product called "Boson Router Simulator" which is a software application that you can practise all these important things on, without the worries of screwing up any actual routers.

I found this software extremely helpful, hope that everyone else does as well.

Go to:

www.routersimulator.com/

to get the demo.

[KorpDeath]

There are switches that do routing also. For instance the Alcatel OmniCore 5052 is a wire speed switch that supports a plethora of routing protocols. (Used to be Packet Engines)
And you CAN use switches at the edge, with ACLs (Access Control Lists).

[gold eagle]

It can be added

switches - also a hardware device

Insofar as switches being cheaper than routers, um, there are many cheap routers and many more expensive ones just like there are cheap switches and expensive ones.

One might want to add the vlan capability with switches.

[KorpDeath]

There is too much to add. I just gave up. What about group mobility? Group mobility is king!

[ammo]

Let's non get confused with the "home router for broadband" with "true" "industrial" routers.

Most "true" routers do not do nat. They concentrate on the routing part. Routing is based on routing tables. Routing tables are either built manually -static-, or dynamically with the use of routing protocols like rip or opsf (http://searchnetworking.techtarget.c...212728,00.html)
(http://searchnetworking.techtarget.c...214265,00.html).
Routing as has been said, acts on OSI layer 3 (network).

- Routers seperate each LAN into seperate subnets, each having a different third 'octet' - ie 192.168.1.1 and 192.168.2.1 - they send data across these subnets.

It's not really about the third 'octet' (byte) but rather about the IP vs the Netmask, ie: it's about matching the network part of the address. Ex: Ip address 192.168.0.1/24 means that the 24* first bits of the address are for the network address, the 8 last bits are for host address (the /24 notation means the first 24 bits of the Ip are for the network address. this is equivalent to 255.255.255.0). However,

Switches can be managed or unmanaged. The act on OSI layer 2, normally, but there are also layer 3 switches (I beleive these used to be called "brouters" as in "bridge" and "router"). Managed switches (usually) CAN allow for redundant paths with the spanning tree protocol; multiple physical paths without the use of STP will result in broadcast storms. Managed switches also make possible VLANs (Virtual LANs) (http://searchnetworking.techtarget.c...213299,00.html).

Swithces should be compared to hubs. In fact a switch is sort of like a hub with bridges on each port. The layer 2 vs layer 3 means that routers can make abstraction of the physical interface. That's the advantage (or rather difference) of routing.


*(this isn't precisely true, since some bits at the begining of the IP address represent the adress class (A, B, C, D, E)


Hope this clarifies things for some....

Ammo