Questions tagged [ethernet]

For questions relating to Ethernet networking, as defined by the IEEE 802.3 standards.

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19
votes
6answers
54k views

Minimum Ethernet Cable Length?

I have heard from a few people that cables less than 1 meter are prone to transmission problems. Is there any minimum copper cabling length? Please explain if this is true or not and share any ...
1
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1answer
77 views

Would multiple connections to a network make the connection faster?

So, in theory, if I connected to a network using, say, 30 ethernet cables from the same PC, wouldn't the upload speeds go up exponentially, because it would split the data over all the ethernet ...
34
votes
5answers
8k views

Why are Ethernet Standards written in the form of 10/100/1000? Why not just 1000?

I always have seen Ethernet Standards written in the form "low value/middle value/max value", and always wondered why. Won't a router just reproduce a lower speeds anything below its maximum if it's ...
2
votes
3answers
613 views

Max bandwidth of wireless access point with gigabit backhaul

I'm looking at setting up a network with full WiFi coverage. Right now I'm still comparing access points to mesh. I see the options for AC access points offer wireless bandwidth in excess of 1Gbps. ...
4
votes
3answers
407 views

A reason why Ethernet has maximum cable length confuses me

The answer in this post suggests that it has two reasons. While the impedance characteristics of a transmission line become less favorable for high speed data as the line gets longer (resistance ...
2
votes
1answer
2k views

Relation between Ethernet and 802.11 headers

I would like to ask about the relation between 802.11 and Ethernet L2 Link layer. Are they dependent of each other? Or can they be seen as independent L2 link layers (with only similarities in ...
25
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5answers
58k views

Why is 4096 the max value for VLANs

The Tag Protocol Identifier is set to 16 bits. In the CCNA certification it is said that it's not possible to have more than 4096 VLANs. 4096 in binary is 1000000000000000. Since 16 bits are allocated ...
7
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4answers
19k views

Minimum ethernet frame is 64 bytes, Why the payload must be padded to at least 46 bytes

What is reason to pad payload to mininum 46bytes, to form a ethernet frame of 64 bytes. Following says min would be 41 bytes. https://stackoverflow.com/questions/14526139/what-is-the-minimum-packet-...
0
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1answer
96 views

Coexistence of different automation protocols in a single application

I was searching for suitable Modbus hardware (we have some already installed) for point-to-point communication via existing network, I came across new EtherCAT one. So wonder if different protocols ...
1
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1answer
36 views

Where I can find frame specification?

When I capture from wireshark traffic I can see data like this Where I can see the specification of each field? When I read wiki https://en.wikipedia.org/wiki/Ethernet_frame there is nothing like ...
1
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1answer
61 views

Can ethernet port be used for getting a signal from passive circuit

If we short circuit RX, TX of Serial port we can detect it by echos. Then we can detect whether Serial port is short circuited or not. Using that phenomenon I can create simple serial socket with ...
1
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1answer
36 views

Half duplex setting switch forwarding frame collides with host forwarding frame

So my question is regarding half duplex switches connected to hosts. Consider a case where a switch is connected to a host by a single link. In an event where a switch decides to forward a frame to ...
4
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2answers
396 views

VLANs isolating networks (VoIP/Wi-Fi)

I have to set up our network in our new office. I'm no networking expert (developer), but I need some input and advice here for some things I wonder about. I have purchased the following: 2 x Cisco ...
1
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1answer
287 views

VMware Ethernet connection to two different switches that are linked together - What can result? [closed]

I have a client that someone in the past setup two NICs on the server to be active on vSwitch0. vSwitch0 has load balancing set for Route based on originating virtual port. Switches are D-Link DGS-...
3
votes
1answer
507 views

Does MACsec (IEEE 802.1AE) support multicast / broadcast?

In general, Ethernet supports both multicast and broadcast. However, once you start encrypting the payload, you need a key management. I am wondering if IEEE 802.1AE supports multicast and broadcast? ...
2
votes
1answer
446 views

Why do I see “ethernet” keyword in my wlan0? [closed]

When I check my wireless network card interface with the command ifconfig wlan0: ether -my-mac-adress- (Ethernet) I just started to learn this stuff, but I thought Wifi and Ethernet are kind of ...
1
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1answer
132 views

How to avoid microbursts causing drops?

I have a network issue that has to do with microbursts. I will first tell a bit about the network: There are 4 Aruba/HP ProCurve switches. 1 Core switch and 3 downstream switches. All connections in ...
2
votes
3answers
636 views

Ping command through network

I have been trying to understand how and what tables are populated ( if they are clean at the start) when a ping command goes through. Lets say I have this network: I want to send a ping command from ...
0
votes
1answer
40 views

For ethernet with bandwidth B, how much time a node has to wait before sensing the channel after the first collision detected?

Let's say one node detected a collision at t=0, in B Mbps ethernet, how long will that node wait before sensing the channel again?
7
votes
1answer
1k views

Run MACsec and VLAN in parallel?

MACsec (IEEE 802.1ae) adds a security tag to an Ethernet frame and encrypts the IEEE 802.1Q field, the EtherType and the payload field. If you want to use VLAN, you need the 802.1Q field to announce ...
4
votes
2answers
9k views

Help optimize a LAG with LACP and two different algorithms on each side

We have a 4Gb (4x1G) LAG trunk with LACP between two cisco switches (c3850<--->c4948) and i am noticing that it is not doing proper load-balancing. I found SW1 using src-dst-ip algorithm and SW2 ...
2
votes
3answers
367 views

How can 1000BaseT transmit on Rx & receive on Tx pins?

How can 1000-BaseT (Gigabit ethernet twisted copper pairs) technology transmit over the Rx pins & receive over the Tx pins? It's baseband technology (hence the name), right? Discrete digital ...
8
votes
1answer
7k views

How can a TCP window size be allowed to be larger than the maximum size of an ethernet packet?

I know that TCP window sizes can be scaled to over 64KB, but looking at an ethernet packet datagram, such as this one: it looks like a layer 2 packet is limited in size to be much smaller than that. ...
2
votes
2answers
150 views

How does the encrypted Wi-Fi protocols relate to ethernet?

More exactly: Which protocol is embedded into which? The relevant Wiki page describes only the protocol, but not its relation to the ethernet. It isn't even made clear if it uses embedded ethernet ...
10
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4answers
2k views

Raw-Ethernet Frames

Recently I was puzzled by the following articles about Raw-Ethernet frames: RAW ethernet vs. UDP Message Passing Using Raw Ethernet Frames Briefly, both of them discusses that it is possible to ...
1
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3answers
92 views

How did one go from IP to MAC in classful networks?

This is more of a question asked out of curiosity than for practical reasons, but it's bugging me, because it might point to a lack of understanding elsewhere. Back when classful IP addresses were ...
5
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3answers
2k views

How to debug L1 Auto negotiation issues?

One of our Linux hosts has started switching its gears recently. While checking the interface speed, I could see that the interface has switched down to 10Mbps. The NIC and Switch are capable of 1G ...
0
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2answers
1k views

How to compute the round trip delay [closed]

I have a query on how to compute round trip delay. I know it is 2 times the propagation time, but let's say I have a packet of 100 bits and a transmission speed of 2 Gbit/sec, how do I compute the ...
2
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2answers
798 views

serial Connecting two network wall sockets

First of all, I am not a network engineer, and my knowledge of physical network installations is quite limited ( I am a programmer ) , so please excuse me if my question is too trivial / naive / ...
3
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1answer
2k views

Data link layer acknowledgement

I'm confused with some concepts please help me out, Data link layer manage flow control hop to hop. Flow control requires acknowledgement receiving but If we observe data link layer header, it does ...
1
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2answers
656 views

Accessing Internet without WIFI or Ethernet

Theoretically, is it possible to access the internet through a browser without connecting to an ethernet cable or using WIFI?
1
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1answer
2k views

What is physically different between 10base-t and 100base-t?

I would assume that the primary difference between 10base-t vs 100base-t is the speed of the clocks interpreting the electrical signal. In other words, if you ensure that a "bit" is transmitted in 1 ...
16
votes
4answers
8k views

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

I know the CAM table in a switch holds MAC addresses and the ports that are associated with the respective MAC addresses. There are no such thing as CAM addresses from my knowledge, so why is it ...
10
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4answers
152k views

What can cause “FastEthernet is up, line protocol is down” on a Cisco Switch?

I wonder what can cause the first line output of the command show interfaces to be: FastEthernet is up, line protocol is down. In other words, Is the cable that is connected to the local interface, ...
6
votes
2answers
2k views

Ethernet padding value

When the data sent in an Ethernet frame is less than 46 bytes, extra padding needs to be added to the payload. The question is: Which is the value of that Ethernet padding? I'm asking since in real ...
3
votes
1answer
813 views

Problem setting up two Wi-Fi module for two way communication

I have two Wi-Fi modules (Moxa AWK 3131) from MOXA. I am trying to set up these two modules in such a way that they can talk to each other. I have connected them as follows, I have configured the ...
1
vote
1answer
107 views

Feeding a PoE capable device with variable power supply over TIA568 A cable (DC spares)

The purpose of such a variable power over Ethernet supply would be to test network equipment that are receiving power over PoE under condition of conditions of low voltage or current and determining ...
3
votes
2answers
7k views

Ethernet padding

I'm using Wireshark for my project. I sent a ping over to Google.com and Wireshark said that the length was 57 bytes(when I received the reply it was 60 bytes long and it contained 6 bits of padding. ...
1
vote
0answers
50 views

How to design network with high availability in a multilevel small workplace [closed]

I want to create a network in my work 4 floors 50m2*4 workplace. Requirements are simple: Share internet ( < 20mb/s ADSL) while blocking someone from abusing download speed for long period. (...
-1
votes
1answer
67 views

Can QSFP28 (aka zQSFP) DACs be used in place of QSFP+ DACs for 40GBase-CR4 Applications?

All: Have an testbed configuration where we're running 24 servers with Intel XL710DA1 40G NIC into a switch with 40/100G ports. Trying to use DACs to hold the cost down, but parsing the specs for ...
-3
votes
4answers
11k views

How Layer-2 data will be fragmented?

Got a doubt while studying about LLC layer. From Network layer I came to know that IP fragmentation will be done, For L4 TCP will segment the data. Here, the question is Protocols starting from Layer-...
1
vote
2answers
493 views

Determine whether the MAC address is of a router or the destination computer?

In a given Ethernet frame containing the HTTP GET message can we tell apart whether the MAC address of the destination is of a router or end host? The link to ethernet-ethereal trace :: https://drive....
3
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2answers
1k views

What are the reasons for ADSL to use ATM instead of Ethernet

I'm a newbie to networking and I wonder what are the reasons for ADSL to use ATM instead of Ethernet ?
0
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1answer
45 views

What is meant by “technology dependent” PHYs? [closed]

Is there something like "technology independent" PHYs? To add the context as Zac67 correctly mentioned, I was reading clause 73 of 802.3-2015. 73.3 - Functional specifications. Excerpt: "The Auto-...
30
votes
5answers
5k views

Why do we still use Ethernet?

There's no doubt the vast majority of Ethernet frames are transporting IP packets. I know there are various other protocols that can be transported over Ethernet as well, but those can be transported ...
-1
votes
3answers
246 views

Why do we need an ethernet MAC address? [duplicate]

Don't think it's a duplicate. I've searched really many articles and couldn't find the satisfying answer. I understand : how ARP works MAC address is an unique address for each NIC IP is network ...
1
vote
1answer
854 views

Setting MAC source address to broadcast

How would a network behave if one were to set the source address of an Ethernet frame to the broadcast address FF:FF:FF:FF:FF:FF? Obviously, one would have to manually alter the relevant field in the ...
11
votes
2answers
1k views

What does the naming convention for ethernet standards mean: 1000BASE-T , BASE-TX, BASE-SX, etc.? What is the meaning of the components of the name?

I understand the number in the naming convention. The number represents how many Megabits per second can the standard support. However, I do not understand the rest of the naming convention. What do "...
1
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3answers
3k views

Can Ethernet use fiber optic cables?

I am new to networking, know about Ethernet and that Ethernet cables exist to make a wired networks. I also know about fiber optic cables which have a glass like material inside and transmit light ...
1
vote
2answers
212 views

What Are LAN technologies?

I know about different LAN topologies(like star, bus, ring,...) and that Ethernet is one of the ways to practically implement wired LANs. I wonder what other technologies exist to make LANs? And, is ...

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