cross-posted from: https://lazysoci.al/post/12597342
Okay, I’ve been watching lots of YouTube videos about switches and I’ve just made myself more confused. Managed versus unmanaged seems to be having a GUI versus not having a GUI, but why would anyone want a GUI on a switch? Shouldn’t your router do that? Also, a switch is like a tube station for local traffic, essentially an extension lead, so why do some have fans?
Some of what others have posted is correct, and others are misleading.
A router is a device that can take your WAN connection (be it ADSL/ADSL2/coax/fibre) and convert the signal WITH a built in MODEM for that particular signal to usable network data (ie packets on RJ45). In the case of fibre, you might even need a fibre-RJ45 converter even before the router.
These routers are often collection of devices to make it convenient to consumers. They will often have a small unmanaged switch of 4 ports, probably WIFI of some flavour, a SIMPLE firewall/DHCP/QoS ability. Routers are sometimes required because what the ISP sends you is not straight “internet”, it might be encapsulated in PPP or similar, and may require you to use credentials to access as well.
Routers have a lot in common to a L3 switch, an fact they basically are the same with one key difference, which is what I first said - a Router device supports different types of WAN interfaces, a L3 switch only deals with RJ45/Fibre type ports.
A proper network would generally be: Internet - Router - Firewall - L2/L3 Switch ---- clients
The link below ignores the firewall because its focusing on what the devices are, but it would be after the router and before the first switch.
https://www.networkstraining.com/router-vs-switch-in-networks/
While most of this is true sometimes, in the spirit of learning I wanted to point a few things out. So in an IP network a router by definition only has one function, connecting two layer 3 networks. Switches and routers are not similar at all because they do not operate at the same layer of the OSI model and do not require each other to function. By definition a router does not really need Ethernet the protocol at all in many situations and definitely doesn’t need to have any type of WAN connection. Now all of that said, many consumer “router” devices are really a combination of the services of several devices used in a large network (usually including a router, firewall, access point, and sometimes other basic IP services like DHCP or a DNS forwarder) so it gets pretty murky.
Another thing is that in larger networks the actual transport (like Ethernet the protocol) or physical medium (Ethernet the cable like cat5/6 or fiber optic) are not related outside of the way that they are configured. What I mean by that is you can run Ethernet the protocol over a fiber optic cable if you want but you can also use the same physical cable type in other situations for other protocols as well (fibre channel storage on OM4 fiber as an example here), the cable does not dictate it directly in most situations. Another example here is ADSL the protocol being delivered over a cat5 cable. Anyway, I hope at least some of that was helpful!
I’ve never seen ADSL (Asymmetric Digital Subscriber Line) delivered over anything other than a phone line (Cat nothing, and usually RJ11 or RJ12 termination). That is what it was designed for.
Both a consumer router, and a L3 switch have a routing table in order to decide how each IP packet will be forwarded through the device. For that to work both a L3 switch and a Router support dynamic routing protocols such as OSPF, RIP etc, or statically configured routes.
The primary use case for a router is WAN connectivity, as I stated. For almost 99% of cases, including failover/redundancy, router connect the WAN network to the beginning of the internal network.
And yes, routers do operate at the same OSI layer, as I said, L3. If they didn’t they could not have a routing table and decide how traffic is forwarded (remember routers still have multiple LAN ports, whilst unmanaged they still have the ability to decide what goes where.
So phone line when it’s 2 pair UTP is also known as Cat3 and you actually brought up something else interesting, the connector also doesn’t determine what the cable is doing either, you can use an RJ45 connector with cat3 cable and the right pins populated to pass Ethernet (up to 1000FX if I remember right) just as you can use 2 pair of a cat5 cable to replace cat3 cable in a pinch.
Back to switches though, a L3 switch is called that (or called a multi-layer switch) because it’s performing functions at multiple layers, I’m just trying to make the distinction that a switch and functions involved in switching does not operate at nor use any parts of the L3 protocol stack as switches do not view network traffic in packets but instead operate using and physical addresses and frames. The same physical device may do both but its import to understand that the device is using different components and logic to perform both functions (for example, a switch forwards frames based on the MAC/CAM table), the reason this is important is that it helps understand how things like VLANs work. Also, while I would agree that in the consumer space a router is 99% for a WAN connection that is definitely not true for routers (or even routing) as a whole, there are way more reasons to use a router between two private networks than just between a private network and the internet (which is what I assume you mean by WAN but that is also not always true).
Firstly Its not cat 3. I’ve never seen that in a telephony installation. Its 4 core flat ribbon or just 4 core. Neither are twisted. Secondly, with 2 “pairs” the best you can do is 100mb/s, as in 10MB/s. Thirdly an L3 Switch DOES use the L3 protocol stack - that is where ROUTING and the routing table happens. OSPF, EIGRP, RIPv2, IS-IS, BGP are all LAYER 3 protocols.
I think you need to go back to school.
https://en.wikipedia.org/wiki/Open_Shortest_Path_First
I like how we are arguing over old stuff that basically doesn’t matter. Do you want to also mention token ring for an achtually statement?
Cat 3 cable can be used in telephony as referenced here https://en.wikipedia.org/wiki/Category_3_cable but it kind of really doesn’t matter for the original poster does it?
You are right that switches can operate at L3 if you have an L3 switch. You can also disable it and make it into this lobotomized brick that just forwards packets based on the CAM table. Guess what layer that operates at? Guess what protocols literally don’t matter for forwarding packets that are on the same L2 network?
@bigredgiraffe is pointing out the distinction between L2 and L3 devices within a network for someone that is learning networking. He is making the clear distinction that NEEDS to be made for someone learning. Not all switches are layer 3, not all switches have layer 3 enabled because they have the feature set, not all networks are created equally.
Maybe instead of helping this guy learn about the distinction between layers, justifications, etc. you can just tell him every switch is L3, uses an overlay, and runs 3-5 routing protocols all redistributing routes to other overlays.
I was networking AUI, before you were born, numb nuts.
Thank you very much. I feel like my knowledge is going Super Saiyan!