Emulate unmanaged switch

I'm required to change from ISP and I will be getting a EMTA (1).
I'll also be having TV from that ISP.
I'm planning to by a switch that will be behind the modem and before my perimeterfirewall, that is the only way to avoied that HGW (2) thing from my new ISP.
That switch will basically split the connection from the modem in two:

  • Ethernet cable to my perimeterfirewall
  • Ethernet cable to my set-top-box

How can I emulate a unmanaged switch using OpenWrt, so I have everything working while waiting for my new switch to be delivered?

Any help is appriciated.

  1. https://en.wikipedia.org/wiki/Cable_modem#MTA
  2. https://en.wikipedia.org/wiki/Residential_gateway

I am guessing that the EMTA you will be getting either has two Ethernet ports, one for Internet service and one for (digital?) TV service, or that it has one port that somehow combines the both (VLANs?). Without knowing those details, including how it splits TV service from Internet service it is difficult to provide more guidance.

OpenWrt, being based on the Linux kernel and common utilities, likely can manage this, perhaps even without another switch. It will likely be configuration of the "WAN" interface and its sub-interfaces to accept and differentiate between the two streams of data, and route the TV-related traffic to a selected port on OpenWrt device.

I'm guessing you are going to want a managed switch not unmanaged. At the least its likely you need vlan support for internet vs TV service.

Following Jef and Daniel Lakeland's answers, I have contacted my new ISP
to get more info on the EMTA capabilities.

Thank you to both of you.