Howdy. We have a bunch of smart folk around here, so I figured I'd ask something ;) I recently got a Cisco layer 3 switch. Never had L3 before, and I was excited to redo my home network and use subnets to divide stuff up. I did 10.0.0.0/24 for servers, 1.0 for misc gear (UPS, RAID controller, etc), 2.0 for IoT, 3.0 for the office switch, 4.0 for the closet switch, 10.0 for workstations and 200.0 for the internet.

Got everything working great. However.. I have switches in two other locations. Problem is, there are two IoT hubs in the closet plugged into that switch so they get like 10.0.4.2 instead of 10.0.2.2. So I figured OK, I'll pick up two more L3 switches. These are ooold Ciscos, 3750s. Probably not the best thing to run for security reasons as they are not getting updates anymore, but then, this is just a personal LAN so I'm not really sweating it lol.

Question is - when I connect the two new 3750s via their 10G uplink ports, do they use the same IOS config? Like can I set ports on the office switch to use VLAN20 for IoT from the primary 3750, or is each switch "an island"? I wasn't sure if they have to work together or not. I've never been a networking guy, this is all new to me :)

I'm also kicking myself for not thinking to look for faster switches before doing this. I just upgraded Comcast to like 1.4G but as my LAN is all 1 G hardware, I'm getting ~950 Mbps at best. Of course, 48 ports at 10G is probably astronomically out of my budget anyway, heh. Could I use the four 10G uplink ports to link my main rig, a file server and the cable modem together?

If I run fiber, does that necessitate two ports each on the uplink for fiber transceivers? I was under the impression you need two, one for upstream and one for down when using fiber. But then, as I said, I'm network-ignorant so what do I know? lol

Anyway, sorry for the wall o' text. Just felt like chatting it up :)

   
--- WWIVToss v.1.52
* Origin: http://www.weather-station.org * Bel Air, MD -USA (11:1/101.0)

Hi, Strahan.

Question is - when I connect the two new 3750s via their 10G uplink
ports, do they use the same IOS config? Like can I set ports on the
office switch to use VLAN20 for IoT from the primary 3750, or is each
switch "an island"? I wasn't sure if they have to work together or not.

They won't synchronise up config, no - it's possible to make them sync VLAN config automatically but the first thing most network guys do is turn that off :)

What you will need to do is add the VLANs onto each switch (assuming they haven't auto-populated already) and connect the switches together using a trunk port (switchport mode trunk). That should, by default, allow all the configured VLANs to pass between the switches.

Note that in this scenario your first switch is still doing all the routing between VLANs, your new switch is not using its layer 3 capabilities. That can be done as well but that would be a much longer post :)

If I run fiber, does that necessitate two ports each on the uplink for
fiber transceivers? I was under the impression you need two, one for upstream and one for down when using fiber. But then, as I said, I'm network-ignorant so what do I know? lol

When you say two ports, do you mean one SFP optical module with a pair of fibres in it or two SFP optical modules with two pairs of fibres?

You only need one switch port (though you can add another for resilience if you want to) and typically that single port will use a pair of fibre strands. I'd expect those to be coupled together into a single plug for convenience.

One thing to note is you need to pair your optical module types to the fibre:

Multimode SFP (10G-SR, 850nm) needs multimode fibre such as OM3 / OM4 which is typically teal or orange with grey plugs
Single mode SFP (10G-LR, 1310nm) needs single mode fibre e.g. OS1 which is typically yellow with blue connectors

I have to dash off now but give me a shout if you have any more questions.

BobW

 
--- WWIVToss v.1.52
* Origin: http://www.weather-station.org * Bel Air, MD -USA (11:1/101.0)

that switch so they get like 10.0.4.2 instead of 10.0.2.2. So I figured
OK, I'll pick up two more L3 switches. These are ooold Ciscos, 3750s. Probably not the best thing to run for security reasons as they are not getting updates anymore, but then, this is just a personal LAN so I'm not really sweating it lol.

We still run a good bunch of Cisco 3750s in production networks at some locations, so you should be all good. :)

Question is - when I connect the two new 3750s via their 10G uplink ports, do they use the same IOS config? Like can I set ports on the office switch to use VLAN20 for IoT from the primary 3750, or is each switch "an
island"? I wasn't sure if they have to work together or not. I've never
been a networking guy, this is all new to me :)

Since you have created all the subnets, I would suggest routing between the two switches. Create a 192.168.100.x/30 and use 192.168.100.1 and .2. You can run a routing protocol like EIGRP and add those to it, along with your 10.x.x.x networks so the routes tables are updated on both.

Some IoT devices like to be in the same subnet for discovery, but if you happen to run into an issue like that, you can add ip helper addresses to the SVIs if needed. That is also how you get DHCP to work on different networks.

I'm also kicking myself for not thinking to look for faster switches
before doing this. I just upgraded Comcast to like 1.4G but as my LAN is
all 1 G hardware, I'm getting ~950 Mbps at best. Of course, 48 ports at
10G is probably astronomically out of my budget anyway, heh. Could I use
the four 10G uplink ports to link my main rig, a file server and the cable modem together?

I'm using Cisco 3650s with some 10G fiber interfaces on them, but also have some 9300s that I will eventually move things to. But yes, I use the 10G fiber interfaces to connect my servers (data and iSCSI).

If I run fiber, does that necessitate two ports each on the uplink for
fiber transceivers? I was under the impression you need two, one for upstream and one for down when using fiber. But then, as I said, I'm network-ignorant so what do I know? lol

Normally they are LC/LC, so technically two fibers - bit they go to the same interface. You would need SFPs and can use multi-mode fiber since the distance is not going to be that long. If using 10G, get aqua OM3 fiber LC/LC patch cables. For 1G fiber, you can use OM1/2 orange multi-mode fiber.

- Mark

:.: Weather Station BBS · telnet://bbs.weather-station.org :.: :.: http://www.weather-station.org/bbs · Bel Air, Maryland - USA :.:
      
--- WWIVToss v.1.52
* Origin: http://www.weather-station.org * Bel Air, MD -USA (11:1/101.0)