35 votes
Accepted

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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21 votes
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How LAN works in video games if only one station is permitted to transmit?

Only one device is allowed to transmit at any given time. At any other given time, another device is allowed to transmit. How can you have a conversation at a dinner table if only person can speak at ...
Jörg W Mittag's user avatar
18 votes

How LAN works in video games if only one station is permitted to transmit?

Some LAN protocols, on some media, are half duplex. That means that only one host on a LAN can send a frame at any given time. The classic example of this is the original ethernet, but the modern ...
Ron Maupin's user avatar
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17 votes

IP addresses from public IP block in my LAN

EDITED I'm assuming you're considering using an IP block that is not registered to you. Otherwise, skip to the last paragraph. Besides being a very poor practice, if you use public addresses on your ...
Ron Trunk'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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12 votes

How is data sent from multiple different sources (computers) to the same destination host (computer) on a local network is handled by switch?

Switches forward all packets it receives to the best of its ability. If is unable to send a packet immediately, the packet is queued in a buffer and if the queue is full, the packet is dropped. ...
jcbermu'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

Can Ethernet frames only be transmitted in a LAN?

No, that's not correct. You don't need a router for two hosts to communicate using IP as long as they're in the same network.
Teun Vink's user avatar
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9 votes
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What precisely is a link?

There is no single precise definition for a "link". A link can be a physical layer connection, two ports connected by a cable. A link can also be understood as general connectivity by data link ...
Zac67's user avatar
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9 votes
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Why isn't 10.0.0.0/8 used instead of 192.168.0.0/16 for private addresses?

It is merely a necessity constraint and personal preference. If a Network is being built that would only have 10, or 20, or 50, or even 100 hosts, there is no reason not to use a /24 from 192.168.0....
Eddie'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

Speed benefits when switching LAN from 1Gb copper to Fiber Optic

You are conflating many things here, so let's try to detangle the issues in your question. Data rate is data rate, regardless of the physical medium. A 1Gb connection has the same data rate whether ...
Ron Trunk's user avatar
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8 votes

Can Ethernet frames only be transmitted in a LAN?

NO. IP packets are encapsulated inside Ethernet frames. It's not one or the other.
Ron Trunk's user avatar
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8 votes

How do two computers with different speeds communicate

I would imagine that with TCP A will resend the packages until it's gotten an acknowledgement for them all which would degrade A's performance because of having to resend packages all day long (...
DRP's user avatar
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7 votes

Why do we use VLAN?

Besides the unknown unicast flooding that you allude to, broadcasts are necessary to the operation of ethernet. Some protocols require broadcasts. For instance, hosts use ARP requests (broadcasts) to ...
Ron Maupin's user avatar
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7 votes
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What are the reasons for not putting multiple subnets on the same VLAN?

There's really no reason not to put multiple subnets on the same VLAN, but there's also probably no reason to do it. Pro: Allows the subnets to talk directly without a router or firewall Save's ...
Dave Noonan's user avatar
7 votes

How do two computers with different speeds communicate

With directly connected computers, both need to use the same speed when sending to each other. Transmitting and receiving with different speeds requires splitting up the data into packets and some ...
Zac67's user avatar
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6 votes

Why do we use VLAN?

There can be many reasons to split a network into VLANs. Security seggregation. You may want to filter or forbid communication between some systems on your networks. Limiting of broadcast (and ...
Peter Green's user avatar
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6 votes

Are there any advantages in using optic fiber to connect a host computer to an Ethernet LAN?

There's several advantages to Fiber-to-the-desk length: copper cabling is limited to 90 meters of horizontal cabling (leaving 10 meters for patching). Fiber doesn't have this limitation. In some ...
JFL's user avatar
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6 votes

How do two computers with different speeds communicate

In addition to the completely correct answers about speed matching directly connected systems ... One of the fundamentals of the internet (including all the private routing portions) is that the ...
jonathanjo's user avatar
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6 votes
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Error Detection across OSI layers confusion

I know that in the data link layer that is responsible ensuring that frames has been transmitted successfully by sending acknowledgement That is incorrect. There are very few data-link protocols ...
Ron Maupin's user avatar
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6 votes
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How is data sent from multiple different sources (computers) to the same destination host (computer) on a local network is handled by switch?

A switch buffers frames - this is in contrast to a repeater hub that can't buffer anything. As @jcbermu has pointed out, both frames from A and B are first stored in their respective ports' receive ...
Zac67's user avatar
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6 votes

How does Ethernet Switch ensures the validity of the MAC address table?

Your understanding is correct, but your assumption that "no frames transmitted from either hosts, C and D." is likely wrong. Gratuitious ARP precisely address this concern. From Wireshark.org: The ...
JFL's user avatar
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6 votes

How does Ethernet Switch ensures the validity of the MAC address table?

Further to JFL's answer, many devices will send gratuitous ARP when the link comes up; switches correspondingly should invalidate their MAC table for a given port when the link state changes. In your ...
jonathanjo's user avatar
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6 votes
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What is the difference between DHCP and NAT?

Missing from the current answers is DHCP is a protocol for configuring hosts, and runs periodically to keep their addresses and other configuration up to date. The traffic is between the host and a ...
jonathanjo's user avatar
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6 votes

How Network layer routing actually works in the physical world

I want to make a few clarifications to @Effie 's answer: The basic idea for this separation, is that each autonomous system can choose how to arrange routing within itself, however routing between ...
Ron Trunk's user avatar
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5 votes
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Why do we use VLAN?

According to my understanding, the network switch will look out for the specific MAC address and then it will forward the frame so basically it doesn't broadcast the frames then why do we make VLANs? ...
Everton's user avatar
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5 votes
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Spurious restransmission to a server behind pfsense NAT

Found it ! It's a bug when running pfsense virtualized -> https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=165059 Workaround is to disable hardware checksum offload box under System > Advanced on ...
aurel's user avatar
  • 81
5 votes
Accepted

Connect a LAN cable to LAN1 & LAN2

You didn't actually connect two router ports, you connected two switch ports. The router has a switch module. You created a layer-2 broadcast storm. Broadcast is an essential part of ethernet. When a ...
Ron Maupin's user avatar
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