18

I am setting up the network for our small companies new office - I have about 20 computers upstairs and 20 down. There is a switch on each floor, the router is downstairs, and a cat5e cable running between floors. All computers should be on the same subnet.

Is there any difference in connecting both switches to the router(Route A) or connecting the switches directly to each other(Route B) and only one switch to the router? I know both approaches will work, just wondering if there is a reason to prefer one or the other. Thanks Network Layout

Tradsud
  • 473
  • 1
  • 3
  • 8

4 Answers4

15

Amongst other things (like what haroldmoma mentioned), another to consider is that if you chain the switches together and the first one dies, the second one will also stop working (everyone is offline). If you attach them both to the router, then one failing won't affect the other (only half the office is offline).

Ƭᴇcʜιᴇ007
  • 111,883
  • 19
  • 201
  • 268
13

When you connect two switches together, you are extending your broadcast domain. The broadcast domain can impose a burden in fairly large networks. When you connect each switch independently to the router, there will be a broadcast domain for each switch, thus controlling the broadcast traffic passing through your network.

haroldmoma
  • 320
  • 1
  • 4
  • 11
  • 7
    While that is normally true, in this case it appears that the side of the router he is plugging in to is actually a switch, and not independent port (correct me if I'm wrong). In this case, there is almost no different in which route he uses, except if the router is only 100mbps and the switches are gigabit. – KJ-SRS Dec 01 '11 at 18:25
  • 4
    I think most home/small business routers, like the ones with 4 ports, simply uses an unmanaged switch controller chip to provide the 4 ports as KJ-SRS describes. One simple indicator is whether the original firmware mandates which port must be WAN. You can also log into the router and run `ifconfig` to see how many ports can be controlled independently. – billc.cn Dec 01 '11 at 18:45
  • 1
    @billc.cn, They often will not show up in ifconfig until you configure them to be. Thats not a surefire test. – user606723 Dec 01 '11 at 19:10
  • 2
    As stated above, the answer is incorrect. In both cases you will only have one broadcast domain, unless the router has the ability to do VLAN partitioning and you configure it to partition. – Collin Anderson Jul 14 '12 at 16:49
  • this answer is way wrong, i think the @haroldmoma meant collision domains. – Tim_Stewart Oct 05 '18 at 15:32
  • @Tim_Stewart it is not, actually. By the wikipedia entry on broadcast domains: "The notion of broadcast domain should be contrasted with that of collision domain, which would be all nodes on the same set of inter-connected repeaters, divided by switches and learning bridges. Collision domains are generally smaller than, and contained within, broadcast domains". https://en.wikipedia.org/wiki/Broadcast_domain – haroldmoma Oct 15 '20 at 05:34
7

If you chain the switches the switch closest to the router will get more traffic than if you had put them parallel (where it will all go through the router) depending on your usage (heavy internet accesses needed vs heavy access to own fileserver) you can weigh one off to the other.

It makes the switch closest to the router a single point of failure (as mentioned by techie007).

ratchet freak
  • 2,854
  • 1
  • 17
  • 14
  • Since almost all low-cost switches use store&forward (rather than cut-through) packet handling, the traffic load can be an issue. Also there is a performance handicap (albeit small) when daisy-chaining switches. A store&forward switch has to fully buffer every Ethernet frame before it can be retransmitted, and this will add to latency. – sawdust Dec 01 '11 at 20:29
0

Other answers here speak about some of the differences. I will get at your following question,

I know both approaches will work, just wondering if there is a reason to prefer one or the other

So let's say you only use your router for access to inet (no VPN or other routing needs)

If I have Router R_A and switches S_A and S_B. Suppose we connect both switches directly to the router. Then suppose I have 2 hosts on S_A (S_A_h1, S_A_h2) and 2 hosts on S_B (S_B_h1, S_B_h2).

If S_A_h1 wants to talk to S_B_h2 how many hops must be made? 3, one through each switch and the router.

If S_A_h1 wants to reach the internet, how many hops must be made in the LAN? 2, one through the switch and one through the router.

Now suppose we connect only S_A to the router and then connect S_B to S_A.

Now if S_A_h1 wants to talk to S_B_h2 how many hops must be made? 2, one through each of the switches.

If S_B_h2 wants to access the internet how many hops must be made? 3, both switches and the router.

So if you want to reduce network latency you will want to set up your network in such a way that reduces hops. e.g. you would probably want to keep your local media server on the same switch as your TV's and your internet access computers on a switch that connects to the router.

gunnerman
  • 9
  • 1