Switches vs. routers

I know that one of the functions of routers is to separate broadcast domains. However, switches can also separate broadcast domains using VLANs. Are routers really necessary in a LAN environment?

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sratakhin

It depends. You need routers to do inter-VLAN routing, so that hosts in different VLANs can talk to each other. On the other hand, layer 3 switches can be used to do the same thing.
You also need a router for the connection to the Internet and WAN links.

FloOz

At my companies current production environment we only have 1 "router", which is the router to our mpls provider. The rest is layer 3 switches (which can perform vlan routing) and layer 2 switches.

YFZblu

That could work at a stand-alone small business where all resources are in the same general vicinity; however that type of topology does not allow for an easy transition for future growth. That said, networks in fast-growing environments are often pieced together rather than systematically designed, so I won't say the OP's scenario doesn't exist in the field.

NetworkVeteran

Michael2 wrote: »

I know that one of the functions of routers is to separate broadcast domains. However, switches can also separate broadcast domains using VLANs. Are routers really necessary in a LAN environment?

While L2 switches can divide a LAN into separate broadcast domains, without a L3 device, systems in one broadcast domain have no means of communicating with systems in the other broadcast domains. So yes, in most cases, you'll still want L3 routing even with VLANs.

(Now, if you involve PVLANs, things get a bit more interesting!)

Prasad Satav

There will be no point in dividing the broadcast domain if you wont be able to route between them, as everybody says.. layer 3 switches can handle that... but I would prefer having a router.. because your Local network definitely needs a WAN connection (Internet) ultimately.

RouteMyPacket

sratakhin wrote: »

It depends. You need routers to do inter-VLAN routing, so that hosts in different VLANs can talk to each other. On the other hand, layer 3 switches can be used to do the same thing.
You also need a router for the connection to the Internet and WAN links.

This is an ideal configuration for small to medium businesses. I have worked in environments like that, good stuff.

sratakhin

Switches have many more ports which makes them more useful for L3 routing.

astrogeek

Routers are not necessary in a modern, well designed network except for connecting to the WAN links. Everything in the distribution and access, (and parts of the core), layers likely would be handled by L2 and L3 switches. L3 switches are much faster than routers and often offer much more features.

However, assuming you are asking in regards to CCNA study material, because this is the CCNA section; ignore all of that L3 mumbo jumbo and just understand that without a router your vlans cannot communicate with one another. The vlans would indeed be separate broadcast domains, but without a router users in either domain would not be able to communicate with each other (which may be an organizations goal), and neither would have internet access without a router as well (which very few organizations would have as a goal

GOZCU

Michael2 wrote: »

However, switches can also separate broadcast domains using VLANs. Are routers really necessary in a LAN environment?

How will you establish the communication between the different Vlan(s) without a router ?

L3 switches are much faster than routers and often offer much more features.

Layer 3 switch is basically a router which has switch functionalities, also expensive....

Yes you need a router

MickQ

As Astrogeek said, for the CCNA you can consider a L2 device to be a switch, and L3 to be a router.

L3 switches combine both aspects of switches and routers, but leave that alone until you pass your CCNA

For now, be content with your Router On A Stick to route packets between your VLANS on your switch.

johnifanx98

MickQ wrote: »

As Astrogeek said, for the CCNA you can consider a L2 device to be a switch, and L3 to be a router.

L3 switches combine both aspects of switches and routers, but leave that alone until you pass your CCNA

For now, be content with your Router On A Stick to route packets between your VLANS on your switch.

This is the most valuable post in this thread for a CCNA preparer like me

Iristheangel

I guess in a theoretical network that would have no connection to the internet or a WAN link and you wouldn't want any inter-VLAN communication, you can use just switches. It's hardly practical though in most business or even home environments. Just my two cents.

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Roguetadhg

I don't see any patch panels... >.> Have mercy on the person trying to move cabling there.

sratakhin

Well, could it be a self-contained network with no connections other than between the switches?