[mustardo]

You might want two or more routers (or network cards) on the same layer 2 (physical) network, if you buy two devices with the same MAC ARP (address resolution protocol) for example can't work. Typically the chip manufacturer "buys" MAC address ranges from IEEE, some cheap chip manufacturers won't. You can sometimes work around this in software by allocating a new random address to the interface

[navanchauhan]

Oh, that makes sense. Thank you!

[hericium]

Here's my recent comment[1] with real life example.

[1] https://news.ycombinator.com/item?id=32211843