CRS112-8P-4S-IN

The CRS112-8P-4S-IN is a small switch where all eight copper ports can feed power, alongside four 1 Gbit SFP cages. That makes it the switch for a floor full of access points, a row of cameras, or a small office where the phones take power over the network cable.

The catalogue files it under switches with the default configuration switch, and the port layout is verified, so you will not see the "port layout not verified" note here.

The ports

• ether1 through ether8: eight 1 Gbit ports, all eight with PoE-out.
• sfp9 through sfp12: four 1 Gbit SFP cages. The obvious place for your uplink to the router or to another switch.

Because the catalogue records eight feeding ports, the PoE-out per port field appears with ether1 through ether8 in its list. Per port you choose auto-on, forced-on or off; the script writes that as poe-out on that port.

The tool knows which ports can feed. About the power budget it knows nothing: not what one port can deliver, not the total, and not what your supply can handle. Switching eight ports on does not mean eight devices come up. Add up what you connect yourself, and see PoE-out per port and Cables and PoE in practice.

The catalogue records no WAN port, which is right for a switch. Which port becomes the trunk is chosen in the VLAN step; by default the Switch role makes the last port a trunk and the rest access ports. See VLANs.

What is inside

From the catalogue: MIPSBE, 128 MB of memory, licence level 5 and the QCA8511 switch chip. With 128 MB the small-board warning does not appear here.

hw_vlan is empty for this model. That means you will not get the note about bridge VLAN filtering and lost hardware offload here: the tool writes the VLAN table in the bridge, and for this model that is the route we take. Leave the Hardware offloading (switch chip) toggle under Ports on.

No radios and no modem, so no Wi-Fi package and no Wi-Fi generation in the catalogue entry.

What it is good at, and where it runs out

Good at: powering and switching eight devices, with a fibre uplink to the rest of the network. For a floor with access points that is exactly the shape; see also Recipe: connecting cameras.

Where it runs out:

• The power budget. Outside the tool's reach, and the most common reason a device does not come up.
• 1 Gbit. No 10 Gbit cages; if you want those, look at the CRS305 or the CRS320.
• Layer 2. In the Switch role nothing is routed.
• No Wi-Fi and no modem. All Wi-Fi roles are greyed out with "No wifi radio", LTE / 5G router with "No LTE modem".

Which roles fit

The catalogue knows this model as a switch, so the roles that route are greyed out with "This is a switch": Home router, Office router with VLANs, VPN gateway, Router + CAPsMAN and Hotspot.

What is left:

• Switch: the role for this device. Every port in one bridge with RSTP, a VLAN table, a static management address on the management VLAN, no DHCP server, no NAT and no routing.
• Harden only (baseline): for a switch that is already running.
• Core router: technically offered, but that role writes routed interfaces without a bridge and does not suit this device.

The quickest route to a working configuration

1. Pick One device and search for CRS112.
2. Pick the Switch role and walk through the wizard.
3. Watch which port becomes the trunk and which VLAN is your management VLAN.
4. Fill in the management address and the gateway; that address will be the only way to reach the switch.
5. Go to advanced, the Ports section, and switch PoE-out on for the ports that actually have something on them.
6. Set an admin password, reset the device and paste the script. See Using the script.

Afterwards check with /interface ethernet poe print what each port is set to.

What trips people up

• Switching eight ports on without doing the sums. Add up what you connect first.
• forced-on when in doubt. Voltage without detection can damage equipment that expects no PoE. Use auto-on.
• Looking for PoE on an SFP cage. Those do not feed, which is why the tool's list leaves them out.
• Locking yourself out. After pasting, the switch is only reachable on the management address in the management VLAN; see Switch unreachable.
• An access point that does not come up. Look at PoE and the cable first; see PoE does not power the device.