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I am currently doing an internship and I hear the IT Director referring to a router port as a NIC. I can't remember exactly what he said. Also, in my Networking+ book it states that each dynamic routing protocols are tied to individual NICs, not the entire router.

So my question is, is there multiple NICs in a router?

  • Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you could provide and accept your own answer. – Ron Maupin Aug 15 '17 at 4:27
  • A Router has a multiple NIC's. Example: D-Link Wi-Fi router has two NIC's. They are NIC and a wireless NIC. The normal NIC is used to access the internet through cable and wireless NIC is used for the Wi-fi. If you observe at the back side of a router, there will be a MAC address, Admin name, Password and a default router IP address. So do you know IP address belongs to which part? It is a Wireless NIC's default IP address. The Normal NIC has also an IP address, but it's a public IP address given by ISP. – Satya Sai Ganesh Manepally May 20 at 16:06
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A "NIC" is a "network interface card" (or, often these days, "network interface controller"). It's set of chips (these days, single chip) which implements the technology for the network interface. An "ethernet controller" will take a short queue of packets and implement DMAing them from RAM, framing the packets (adding the source address and ethernet CRC). A modern ethernet controller will also be able to do some Network and Transport layer functions so that the CPU can handle packets more efficiently -- these "offload" functions include calculating checksums and packetising TCP segments. The controller might also implement the more physical aspects of the ethernet protocol, such as Base-T's autonegotiation, or it might leave this to another chip we call a "PHY".

The "ethernet contoller" for a switch takes this to extremes, implementing the entire "transparent ethernet bridging" forwarding plane between 4 to 16 ports. Recent controllers will handle most of the ethernet bridging control plane too.

In almost all modern router designs the router ports attach to one or more switch ethernet controllers, typically a Broadcom Trident- or Tomahawk-series controller. That controller might implement the router's forwarding plane, or it might simply handle port fan-out.

So, back in the IT Director's day routers would have a single ethernet port attached to a single ethernet network interface card, there might be four of these cards assembled with some routing logic to make a "line card". The "line card" would attach to the router's backplane.

Today even a low-end server NIC will happily present 4 gigabit ethernet ports. A switch or router might present 16 ports from the one ethernet controller. So your IT Director really should starting saying "port".

But before you go accuse your Director living in the past, consider that the job of a IT Director doesn't allow much time for the details of the technology; that's surprisingly low on the list of things they'd most like to know. So as much as they are being wrong in their terminology, bringing it to their attention in anything other than an aside, is to be wrong from the point of view of their expertise -- management. They have things to do with their time which are much more significant. I'd go no further than "just so you're not embarrassed in a presentation, they call them 'ports' these days".

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There are multiple network interfaces in a router. Routers route between networks, so there must be at least two, often more, network interfaces in a router. Sometimes, the network interfaces are logical, and you can't really call a logical interface a NIC.

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    For completeness, there is a (rarely used) scenario where a router only uses one NIC, aka router on a stick. Often (but not always) this will use logical interfaces as Ron mentions. And it depends on what you call a NICS, does that include e.g. ISDN, DSL or cellular interfaces? – hertitu Oct 9 '16 at 7:20
  • You could technically have a router with a single physical interface, with multiple sub-interfaces all using different VLAN IDs, connected to a switch with the connections to pass the traffic accordingly, such as connections to the internal LAN and an uplink to the ISP. – Jesse P. May 21 at 1:20
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    @JesseP., I thought that was what I explained. The router has multiple interfaces, but logical interfaces probably are not NICs. – Ron Maupin May 21 at 1:25
  • @RonMaupin It is. I was giving an example. That how some virtual appliances work in clouds such as AWS (by default at least), such as pfSense - one interface for everything. – Jesse P. May 21 at 1:29
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This is mostly a terminology question, so here's my 2 cents.

Purpose-built routers do not have NICs, they have physical ports/interfaces, which can be used for many different applications, and internal (logical/virtual) interfaces that can be defined in software.

Servers and VMs however have NICs, they are what connects the server/VM to a switch/router.

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IMHO it is not necessary to bind physical network port and routing. You may successfully route between VLANs and have NO L3 ports at all (just trunk and access ports).

Dynamic protocols are not tied to anything. They use "interface" to control dynamic routing announcement and for many other things.

Yes you can use any computer with multiple NICs as a router. I think you mis-understood your IT Director. I do NOT think it will be proper use of the term NIC for the router. I think you have to use "interface" or may be "network port" word.

Good luck.

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    If you have multiple VLANs, you require a router to get from one VLAN to the other, even if it is a layer-3 switch. Layer-2 switches with multiple VLANs simply cannot get traffic from one VLAN to the other. – Ron Maupin Oct 10 '16 at 3:48
  • You don't require a router, you require a device above the link layer. An application-layer gateway will do the job just as well. – vk5tu Oct 10 '16 at 4:24

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