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Why is the CAM table in a switch called CAM table and not MAC table even though it holds MAC addresses?

CAM (Content Addressable Memory) is memory that can be addressed by content, rather than a numeric memory address. You can look up the interface by presenting the memory with the MAC address. This is ...
Ron Maupin's user avatar
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34 votes
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How does a switch learn a MAC address not in its lookup table?

Good question. I'll answer it with an animation: When Host A sends the frame, the switch does not have anything in its MAC address table. Upon receiving the frame, it records Host A's MAC Address to ...
Eddie's user avatar
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22 votes

Does every host on the LAN share the same ARP table, or do hosts keep them individually?

Actually, every interface in a device has its own ARP table. A host could have several ARP tables (one for each interface it has). ARP tables are not shared between hosts, or even among interfaces in ...
Ron Maupin's user avatar
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22 votes
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What is the least possible separation of two NICs with the same MAC address?

Suppose you have two NICs with the same MAC address, but not necessarily the same IP address. You can't have that within the same link-layer segment. Identical MAC addresses will disable reliable ...
Zac67's user avatar
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17 votes
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Why the first octet of a MAC address always end with a binary 0?

You may notice that two least-significant bits of the most-significant byte of a 48-bit MAC address are usually set to 0 (as in all your examples). There are two flags in the most-significant byte of ...
Ron Maupin's user avatar
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17 votes

How Does A Layer 2 Switch Differentiate Between Different Networks?

A (layer-2) switch doesn't care at all about the IP networks you run through it. however, no normal traffic can occur between two nodes on two different networks. That is correct. Different IP ...
Zac67's user avatar
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16 votes

Why do we need MAC Address if we can uniquely identify each machine with an IP Address

There is a historical reason for this, as @ronmaupin alludes to. In small networks, you don't need a layer 3 protocol. All the devices are directly addressable, so layer 2 addresses work fine. As ...
Ron Trunk's user avatar
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15 votes

Why is the CAM table in a switch called CAM table and not MAC table even though it holds MAC addresses?

CAM - Content Addressable Memory, referring to the memory used for the MAC address table. It works kind of reverse from RAM, you address it by giving it content and it returns you the address where ...
manish ma's user avatar
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13 votes
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What are EUI-48 and EUI-64?

Historically, both EUI-48 and MAC-48 were concatenations of a 24-bit OUI (Organizationally Unique Identifier) assigned by the IEEE and a 24-bit extension identifier assigned by the organization with ...
Cristina Gaucan's user avatar
13 votes

Do routers change MAC address of packets when forwarding

When a frame comes into a router, the router strips off and discards the frame, losing any layer-2 addressing, including MAC addresses. The router will build a new frame for the next interface. Not ...
Ron Maupin's user avatar
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12 votes
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Does a switch always get a MAC address from a PC?

A switch learns the source MAC from the sender. If the destination is not in the CAM table, the switch floods the frame out all ports. So if the receiver never responds, the switch will never learn ...
Ron Trunk's user avatar
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12 votes
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Does Switch need its own MAC address?

The basic function of a switch is transparent bridging - for this, it doesn't need any MAC address of its own. However, if you need to talk to a switch - ie. a managed switch - then that switch ...
Zac67's user avatar
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Does an unmanaged switch deal with IP addresses at all

An unmanaged switch doesn't use/care for/understand IP addresses at all. A managed L2 switch uses IP addresses for management only. Some L2 switches also support limited L3/IP functionality like ACLs. ...
Zac67's user avatar
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11 votes

Do Bluetooth Devices have MAC address with the same specification as the MAC addresses of the Ethernet and Wi-Fi Network cards?

Bluetooth devices are required to have a unique device address, assigned from the same registry as Ethernet and Wifi MAC addresses. Quoting the Bluetooth specification version 5.0 volume 1: Each ...
fgrieu's user avatar
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10 votes
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Why don't we use MAC address instead of IP for having "Internet" or doing communication?

MAC is Media Access Control which provides physical connectivity only. IP Address provides Host or Network interface Identification and Location addressing. For your second question, Let we have two ...
Puneet Dixit's user avatar
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What does a switch do when the destination MAC address is unknown?

I think you are confused. The destination MAC address for any destination not on your LAN is the MAC address of the gateway configured in your source host. MAC addresses are layer-2 addresses, and ...
Ron Maupin's user avatar
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9 votes
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What MAC, IP and IPv6 addresses should I use as example for testing and documentation?

To quote from RFC 5737: The blocks 192.0.2.0/24 (TEST-NET-1), 198.51.100.0/24 (TEST-NET-2), and 203.0.113.0/24 (TEST-NET-3) are provided for use in documentation. And RFC 5156: The 2001:db8::/32 ...
Ron Trunk's user avatar
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9 votes
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Why do we need MAC Address if we can uniquely identify each machine with an IP Address

Don't confuse the network layers. Each layer has a specific purpose. Also, don't assume that there is only one protocol for each layer. Layer-2 has many protocols, some of which use MAC addresses, and ...
Ron Maupin's user avatar
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9 votes

Does every host on the LAN share the same ARP table, or do hosts keep them individually?

To answer the question another way: what mechanisms might be available to share an ARP table? This is one of the fundamentals for IP over ethernet (and any similar layer 2 network). If a device was ...
jonathanjo's user avatar
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9 votes
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How Does A Layer 2 Switch Differentiate Between Different Networks?

The switch doesn't even "see" what is going on above MAC layer. However, hosts are usually configured to send packets to another IP subnet via a default-gateway IP address. So the hosts ...
manish ma's user avatar
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8 votes
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Strange router's MAC address from ICMP Echo Reply?

You are confused. What you claim is your router's MAC address is not your router's MAC address. The MAC address is in the range, 0000.0C07.ACxx, which is the MAC address range for HSRP. The 06 on the ...
Ron Maupin's user avatar
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8 votes
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Why do LANs use MAC addressing instead of IP addressing?

You need to understand the network layers. They are independent of each other. Ethernet and IPv4 are currently the dominant protocols, but that was not always the case, and IPv4 is being replaced with ...
Ron Maupin's user avatar
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8 votes
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Is there a way to "Pass through" a MAC address on a Cisco Switch?

We hope you will become a contributing member of this community. Switches do not change MAC addresses, so your application, if it is on the same subnet, will see the sender's MAC address. If you the ...
Ron Trunk's user avatar
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8 votes
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Is it possible to perform a Layer 2 (MAC address) traceroute?

But is there any way to do a traceroute that will show Layer 2 information? Short answer: no. Longer answer: traceroute exploits IP's TTL feature. There is no such concept in Ethernet, hence no ...
Zac67's user avatar
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8 votes
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Why would a switch ever send an ARP request for a MAC address when it can just wait for the first packet to be received from a device?

You are confusing switching, where a switch creates and updates a MAC address table as frames pass through it, with the switch management. Switching is a layer-2 function, and a dumb switch will ...
Ron Maupin's user avatar
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8 votes

Why the first octet of a MAC address always end with a binary 0?

First, the far most right bit of a byte is the first bit (and not the 8th). And as often in IT fields, first means 0 and not 1. Now, to answer your question, the bit 0 of the first byte of a mac ...
Nakrule's user avatar
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7 votes

How does a switch learn a MAC address not in its lookup table?

The switch doesn't use ARP, but ARP can help in preventing this situation from occurring in the first place, for two reasons: If node A is sending an IP packet to node B which isn't in its ARP cache, ...
hobbs's user avatar
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7 votes

Why don't we use MAC address instead of IP for having "Internet" or doing communication?

1. The reason for that is the routing. If you have an IP, for example 104.103.84.161 for the www.microsoft.com, every router on the Internet knows, where to send packets to this IP address. They are ...
peterh's user avatar
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7 votes
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Practical difference between MAC-48 and EUI-48

1.What is the practical difference between MAC-48 and EUI-48 ? 2.If EUI-48 is not "MAC Address", then how has it made MAC-48 obsolete ? 3.If MAC-48 is burned-in-address and is stored in ROM ...
jonathanjo's user avatar
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7 votes
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Switch MAC learning problem

A problem is that your MAC addresses have the I/G bit set to indicate that they are group addresses, not individual addresses. Group addresses are not allowed to be source addresses, only destination ...
Ron Maupin's user avatar
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