Options
Dumb question but why not use routers instead of switches?
SurferdudeHB
Member Posts: 199 ■■■□□□□□□□
in CCNA & CCENT
I don't fully understand why in a network switches are used since they only do layer 2 switching and it seems that routers are more intelligent to route packets.
Comments
-
OptionsKaminsky Member Posts: 1,235Basic idea:
Layer 2 switches collect multiple host traffic and bring their traffic into the network from that local area. Routers move traffic around edges of areas and provide the core of the network. More powerfull/expensive switches can also concentrate switch traffic and route them in larger networks as can more powerfull/expensive routers do for the smaller routers.Kam. -
OptionsTurgon Banned Posts: 6,308 ■■■■■■■■■□SurferdudeHB wrote: »I don't fully understand why in a network switches are used since they only do layer 2 switching and it seems that routers are more intelligent to route packets.
One school attempts to do precisely that when it's practical to reduce the potential of spanning-tree conplexities and other L2 issues. Constraints include port density of routers vs switches and L3 lookups as opposed to ASIC switched frames. Remember that many switches today are L3 capable. -
Optionshuman151 Member Posts: 208they are referred to as multilayer switches. You can make any port into a routing port by using the "no switchport" command.
in many situations you just do not need the capabilities of a router.Welcome to the desert of the real.
BSCI in Progress...
Cisco LAB: 1x 2509
1X2621
1x1721
2x2950
1x3550 EMI -
OptionsSurferdudeHB Member Posts: 199 ■■■□□□□□□□So what's the difference between MAC forwarding and IP routing? Is MAC address intended for LAN's specifically?
-
OptionsForsaken_GA Member Posts: 4,024You could theoretically use the mac address as a layer 3 address if the layer 3 protocol was coded to handle it (there are ipv6 addressing scheme's that do that, in fact), but in the ip4 world, yes, the mac address is layer 2 relevant, which is why you need things like arp, rarp, and proxy arp
-
Optionsphoeneous Member Posts: 2,333 ■■■■■■■□□□SurferdudeHB wrote: »I don't fully understand why in a network switches are used since they only do layer 2 switching and it seems that routers are more intelligent to route packets.
Why seperate a city into zip codes? Why have different gates at an airport? A layer 2 switch performs different duties and has different responsibilities than a router does. -
Optionstiersten Member Posts: 4,505Work out what the price would be for a 24 port router which can do wire speed switching between all ports
-
Optionstech-airman Member Posts: 953SurferdudeHB wrote: »I don't fully understand why in a network switches are used since they only do layer 2 switching and it seems that routers are more intelligent to route packets.
SurferdudeHB,
Think of it in terms of IP addressing, you know, your favorite subject, subnetting.
With a basic unmanaged Layer 2 switch, like a Cisco/Linksys switch, you can plug two computers into the switch that are in the same IP subnet as follows...[Comp1 = 192.168.1.1/24]---[Unmanaged Switch]---[Comp2 = 192.168.1.4/24]
Now, let's look at the same situation using a router instead of an unmanaged switch...[Comp1 = 192.168.1.1/24]---{192.168.1.2/24}[router]{192.168.2.3/24}---[Comp2 = 192.168.2.4/24]
So in the situation of the Unmanaged Switch scenario, you only use two IP addresses. In the situation of a router: 1) you need to have two separate subnets on both sides of the router 2) you need an IP address for each router interface 3) you need one IP address for each computer. So even in this simple scenario, you will need four (4) IP addresses just for two computers on opposite side of a router.
Now if you want to add another computer to a router, you'd need: 1) another router interface 2) resubnet another subnetwork for the new computer, e.g. 192.168.3.0/24 3) assign a new host address to the new computer, e.g. 192.168.3.2/24.
As you can see, the workload just gets higher and higher if you used a router instead of a switch.
Are you starting to see the relative benefit of a switch compared to a router? -
OptionsSurferdudeHB Member Posts: 199 ■■■□□□□□□□tech-airman wrote: »SurferdudeHB,
Think of it in terms of IP addressing, you know, your favorite subject, subnetting.
With a basic unmanaged Layer 2 switch, like a Cisco/Linksys switch, you can plug two computers into the switch that are in the same IP subnet as follows...[Comp1 = 192.168.1.1/24]---[Unmanaged Switch]---[Comp2 = 192.168.1.4/24]
Now, let's look at the same situation using a router instead of an unmanaged switch...[Comp1 = 192.168.1.1/24]---{192.168.1.2/24}[router]{192.168.2.3/24}---[Comp2 = 192.168.2.4/24]
So in the situation of the Unmanaged Switch scenario, you only use two IP addresses. In the situation of a router: 1) you need to have two separate subnets on both sides of the router 2) you need an IP address for each router interface 3) you need one IP address for each computer. So even in this simple scenario, you will need four (4) IP addresses just for two computers on opposite side of a router.
Now if you want to add another computer to a router, you'd need: 1) another router interface 2) resubnet another subnetwork for the new computer, e.g. 192.168.3.0/24 3) assign a new host address to the new computer, e.g. 192.168.3.2/24.
As you can see, the workload just gets higher and higher if you used a router instead of a switch.
Are you starting to see the relative benefit of a switch compared to a router?
Yes I see, that make sense, thank you.
And subnetting is so... fun -
Optionsthenjduke Member Posts: 894 ■■■■□□□□□□Routers do not send Broadcast Traffic and think about the OSI layer.CCNA, MCP, MCSA, MCSE, MCDST, MCITP Enterprise Administrator, Working towards Networking BS. CCNP is Next.
-
Optionsncsugrad2002 Member Posts: 131K, everyone else has made this complicated.
I'll make it simple.
Switches=hardware based. Think fast.
Routers=software based. Think not so fast. They have routing tables to go through for every packet, blah blah blah.
There's more to it than this. But having a 48 port router isn't such a good idea..not to mention it's expensive
(although cisco actually did something similiar with their lowest level L3 switches, haha.. I'll find the model # sometime) -
OptionsJavonR Member Posts: 245ncsugrad2002 wrote: »K, everyone else has made this complicated.
I'll make it simple.
Switches=hardware based. Think fast.
Routers=software based. Think not so fast. They have routing tables to go through for every packet, blah blah blah.
There's more to it than this. But having a 48 port router isn't such a good idea..not to mention it's expensive
(although cisco actually did something similiar with their lowest level L3 switches, haha.. I'll find the model # sometime)
Dang, beat me to it.
But I would also like to reinforce, switches = very fast, routers = not so fast. -
Optionsphoeneous Member Posts: 2,333 ■■■■■■■□□□Routers do not send Broadcast Traffic
Not entirely true. Frame Relay actually has a broadcast command.
Frame Relay Commands -
Optionsthenjduke Member Posts: 894 ■■■■□□□□□□CCNA, MCP, MCSA, MCSE, MCDST, MCITP Enterprise Administrator, Working towards Networking BS. CCNP is Next.
-
OptionsTurgon Banned Posts: 6,308 ■■■■■■■■■□
As does ATM although we need to be careful here about confusing the broadcast behavior of routers with that of WAN technologies.