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I read that NICs in modern routers are responsible handling of multiple ports.

Is it true to say that every port has a different MAC and IP address, and thus a NIC might have multiple different MAC and IP addresses (corresponding to the appropriate ports)?

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  • Every router interface for data-link protocols that use MAC addresses (not all data-link protocols use MAC addressing, only the IEEE LAN protocols do, and some are 48-bit MAC addresses, while other use 64-bit MAC addresses) have unique MAC addresses.
    – Ron Maupin
    Aug 30, 2019 at 20:46
  • an interface is must be a physical port/NIC ? Aug 30, 2019 at 21:09
  • No. Most business-grade routers will let you configure virtual interfaces, too. Loopback interfaces, BVIs, subinterfaces, etc.
    – Ron Maupin
    Aug 30, 2019 at 21:10
  • So, Technically, a physical port might be connect to virtual interfaces, and have multiple MACs and IPs? Aug 30, 2019 at 21:16
  • A physical interface connects to a physical interface in another device. There are cases where you may configure virtual interfaces in a router for a single physical interface. There may also be virtual interfaces that have no relationship to a physical interface.
    – Ron Maupin
    Aug 30, 2019 at 21:19

1 Answer 1

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I read that NICs in modern routers are responsible handling of multiple ports.

A router port is normally equivalent to a host NIC. Some routers support switch groups where the layer-3 'port' is more a virtual NIC or a router port connected internally to a built-in hardware switch.

Is it true to say that every port has a different MAC and IP address, and thus a NIC might have multiple different MAC and IP addresses (corresponding to the appropriate ports)?

Normally, yes. A router requires multiple ports in order to connect to different subnets. Each port (not necessarily equivalent to physical ports, see above) uses its own MAC address and IP address and each port may have multiple IP addresses (also pretty common with hosts) and even MAC addresses (e.g. virtual MAC addresses in failover scenarios).

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  • So a physical port might have a number of MAC addresses? Aug 30, 2019 at 21:06
  • And what do you mean by "virtual port" Aug 30, 2019 at 21:08
  • Yes, a physical port may use multiple MAC addresses. A virtual port is a port that is not directly mapped to a physical port. Think of two physical ports in a failover group that are treated as one logical port.
    – Zac67
    Aug 30, 2019 at 21:59

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