Can I use a router as a switch?

[CarpeDeo]

I was wondering if I could use a 4-port router as a switch w/o using the gateway part. 4-port routers go for only $40-$50 nowadays, and I figured I might as well get one of those instead of a 5-port switch for $50 if I can. I already have a 4-port router, but I need to hook up two more computers, so can I just daisy-chain it as if it were a switch? Possible?

 

[Stealth1024]

as a very expensive one possibly...

 

[me19562]

Sure u can, the router features dont work if u dont configure those features, but the switch is always working. In reality its r a switch router no router switch.



Good Luck

 

[CarpeDeo]

Stealth1024- Do you know where I can get a switch for less than $40? I can get a 4-port SMC barricade for $40 after rebate . . .

me19562: So I just connect the Uplink of my current router to the WAN of my new router?

 

[nxh]

definitely and it's more efficient than a switch

 

[Rainsford]

<< definitely and it's more efficient than a switch >>



What is more efficient? The router with a switch is just a switch attached to a router in the same box.

 

[Mday]

technically, a router is NOT a switch, and cannot do what a switch can.

but those "gateways" for dsl\cable modem sharing are routers WITH a switch in one piece. since they do have a switch, sure you can use it as a switch =P, just don't use the WAN port.

if you already have one of those broadband routers, just get a switch if you want to expand your network beyond the broadband router's ports. you just hook the uplink port of the switch to a regular port of the broadband router.

if you have no need for another router, get a freaking switch, not another broadband router.

 

[me19562]

Let explain to u guys. All these gateways r nothing more than a Layer 3 switch. What is that?
A layer 3 switch is a switch with some capabilities of a router. For example these gateway make routing from ethernet to ethernet. And can make some others things. A very powerfull layer 3 switch is a Cisco 2948G-L3, this guys have 48 ports 10/100 and 2 1000Gbit. This baby can make almost all the things that can make a Cisco router 2600 series without any wan interface card. U can make aprox. 4096 vlan, access-list, static routing, dynamic routing(RIP,IGRP,EIGRP,OSPF),VTP, etc. This switches r normaly used in the distribution layer. Know guys u have an idea of what u have. I have a SMC barricade and for me in my home works great.

 

[Rainsford]

<< Let explain to u guys. All these gateways r nothing more than a Layer 3 switch. What is that?
A layer 3 switch is a switch with some capabilities of a router. For example these gateway make routing from ethernet to ethernet. And can make some others things. A very powerfull layer 3 switch is a Cisco 2948G-L3, this guys have 48 ports 10/100 and 2 1000Gbit. This baby can make almost all the things that can make a Cisco router 2600 series without any wan interface card. U can make aprox. 4096 vlan, access-list, static routing, dynamic routing(RIP,IGRP,EIGRP,OSPF),VTP, etc. This switches r normaly used in the distribution layer. Know guys u have an idea of what u have. I have a SMC barricade and for me in my home works great. >>



Any router is a layer 3 switch. Why? A switch "routes" packets based on the MAC address, that would be the 2nd Layer. The 3rd layer is the network layer, which is what a router uses to route packets. A "Layer 3 Switch" is a router by definition. Some routers have more or less features, but any device that routes packets using the 3rd layer is a rotuer. Any device that uses the 2nd layer is called a switch. I hub only operates on the 1st layer, the physical layer, which is why is can't do any type of routing. But switches do not use the 3rd layer (as far as I've heard from Cisco's CCNA program), routers do. That's the difference. Perhaps I'm wrong, if so, please tell me. But I have never heard of a switch that routes based on layer 3 information.

Edit: On the other hand, most of the cheap consumer routers do not have typical router features like route learning. Real routers know every step (or most of the steps) from their interface to the destination, something the cheap routers typically do not. So actually I suppose these cheap routers just switch based on layer 3 information and have more in common with switches than real routers. But the fact that they use layer 3 makes them routers, correct?

 

[me19562]

Ok, no because a switch is a layer 3 switch make it a router. why? because the switch still works in the layer 2 and when u configure the layer 3 features then the switch start to work as a layer3 device. I know u heard somewhere about the wirespeed routers, these wirespeed routers r nothing more than a layer 3 switch. The most big difference is these layer 3 switches r hardware based thats why r called wirespeed routers, in the other hand the routers makes all the calculations and decisions by software . Actually u cant difference between one or another these days at least u check in the manufactures website which is which, because the high performance switches today can make a lot of things.(i.e Cisco Catalyst 5000, these is the only switch in the cisco products that make the the 3 logical layers in the networking design for cisco design guide, The Core layer, the Distribution layer and the Access layer).

 

[Rainsford]

Just out of curiosity, what layer 3 features do some switches have? Can switches use access lists? We had some nice routers in my Cisco class, but we didn't do a whole lot with switches outside of VLANs and stuff like that. Our teacher started with routers and we spent way too much time on that so we didn't have enough time to cover everything on switches.

 

[spidey07]

switch = multiport bridge = layer 2 device
router = gateway = layer 3 or higher device

switching router = full featured router that can accomplish the switching of frames based on layer 3 information
routing switch = switch with some routing functionality built-in

this really gets into marketing (which is bad for engineers). When you ask what features do a layer3 switch have...well now that just depends on the model.

2948g-L3s are quite crippled when it comes to full protocol support and features
6500/msm is very fast using ASICs but also limited protocol support and features
6500/msfc is very fast and has full IOS support.
7500s/12000s are ridicously fast, do most route processing in hardware and have full IOS support.

really just depends. I doubt these home gateways have any kind of ASIC technology, but do all processing in software.

 

[Rainsford]

Hmm, I think I get it now. Sounds like maybe the engineers should be naming this stuff instead of the marketing people (yeah right, like that ever happens). Anyways, thanks for the feedback.

 

[Garion]

One note on Spidey's explanation. Layer 3 switches are used for performance. A conversation between two machines is sent through the routing engine of the switch once, which determines the correct destination VLAN/port. The switch then "learns" that path and can then transmit future packets without going through the routing engine again. It is EXTREMELY fast. Lots of other bennies of a layer 3 switch vs a router. You can have as many interfaces as you want, you don't have to buy a separate router, the traffic into and out of a router port isn't limited by the port speed, etc. Layer 3 is very good.

Me19562, I think you're getting the word "layers" confused. When we're taking about layers in networking it isn't Cisco's design guide layers - We are talking about the OSI model that defines how devices and applications communicate. Layer 1 is the physical layer - the cable between two boxes. Layer 2 is the Datalink layer - How signals are sent across that wire. (Ethernet is an example of a Layer 2 protocol). Layer 3 is the Network layer, where TCP functions. IP is Layer 4, the session layer. - TCP, UDP, ICMP, etc. are all parts of the IP protocol. A layer 3 switch works at the network level, sending traffic between different subnets in addition to it's Layer 2 work. Plain Layer 2 switches just forward Ethernet frames based on Ethernet address, useful for a flat network but doesn't do much for a huge routed network.

Oh, and a 2948G is a very low-end Layer 3 switch. It runs a really wierd IOS and performance isn't so hot. The 4000 series is good, the 6500 rocks and the 8500 is unreal. Of course, an 8500 can cost $200K+, so it's a bit out of most users' price range.

- G