Questions tagged [ethernet]
For questions relating to Ethernet networking, as defined by the IEEE 802.3 standards.
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Ethernet Payload Data Size [duplicate]
In an Ethernet Frame, Why The Size Of The Payload Data Is Limited Between (64 - 1500) Bytes, Why Not Less Or More?
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Why do I need to add 4 dummy bytes after the full MAC frame before starting the interframe gap for a proper diassembly? [on hold]
I discovered I have to add 4 dummy bytes in my FPGA core to the MAC layer packet in order for Wireshark to find the CRC valid: if I don't add it, Wireshark considers the last 4 bytes of the payload as ...
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0answers
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Jumbo Frames confusion? [closed]
I'm trying to enable jumbo frames. I have a linux client & a windows server. I've standardized across the board on intel nics. On the windows server the only choice for jumbo frames is 9014 & ...
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2answers
42 views
How does ethernet understand what is the upper layer? What are the values in Ethernet II field?
How does ethernet understand what is the upper layer of a frame? What are the values in Ethernet II field?
Ethernet is in data link layer, so the upper layer is network layer.
When processing at ...
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0answers
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Weird problem in pinging [closed]
Does simple NICs on PCs understand 802.3 frame format packet?
Actually, I can ping my pc by DIX frame format(Ethernet II), but when I switch to 802.3 frame format, pinging my pc is impossible.
Is it ...
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1answer
29 views
Does the PHY signal interframe gap to the MAC?
I'm trying to decode an Ethernet II frame with type instead of length indication. Theoretically this should be done by receiving and storing the data between start of frame and interframe gap. However ...
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5answers
12k views
Is Ethernet port blinking really useful?
This question may not look as an important one and in fact it is just out of curiosity.
But to the point:
Is Ethernet port blinking really useful?
Ethernet ports usually have two light indicators ...
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1answer
30 views
10 Gbit Network without Additional Switch
I've a question about my current setup:
I don't want to buy additional 10G SFP+ switch. May I use R710's new Intel 10G Ethernet's second port to connect additional servers into my network? What is ...
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1answer
90 views
Can I aggregate multiple uplink ports between Ethernet switches?
Disclaimer: I'm not a network engineer; I just have to try to do a good-enough impression to solve this problem.
We have two rooms in our office. In the first, I would like to put a large copper 10-...
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1answer
44 views
Which layer and protocol takes care of power-down and power-up of ethernet port
Which layer and protocol takes care of power-down and power-up of ethernet port (based on cable connected or disconnected) in a Linux machine.
I think it (power-up and power-down) will be taken care ...
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1answer
83 views
To what address does ARP reply in the presence of MAC masquerading
The ARP packet has a duplicate of the sender/destination hardware address. Theoretically, you could have a case where a device sent
Layer2: From AA:BB:CC:DD:EE:FF To FF:FF:FF:FF:FF:FF
Layer3: ARP ...
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1answer
33 views
tcpdump - bogus ethernet address
I'm trying to capture packets on an interface.
The command is as follows
tcpdump -ni any port 1812 or port 1813 or port 3799 or port 8080 or port 15001 -s 0 -w /var/tmp/lb01_trace_$( date +'%Y-%m-%d %...
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4answers
326 views
What is the difference between Ethernet types, considering bandwidth?
Different types of Ethernet (standard Ethernet, Fast Ethernet, Gigabit Ethernet) have different speed of data transfer (10 Mbit, 100 Mbit, 1 Gbit). Why is that?
On the physical layer, the speed of ...
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1answer
53 views
How 1gbe works in full duplex? [duplicate]
1gb Ethernet works in full duplex and the maximum theoretical throughput is 2Gbps. Every pair gives 250 mbps in both directions. How it can work in full duplex on the one pair?
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1answer
45 views
Influence of a TAP
I want to use a passive TAP to sniff all the network (100 Mbps full duplex twisted pair).
I have two interfaces for sniffing and only one pair for each direction. Will the TAP add any noise? Or if I ...
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4answers
32 views
Why RJ45 8-Pin (Cross Connection) is used instead of Straight Connection between 2 computers or Network [duplicate]
I am kind of new in networking.
I want to ask a question about a distinguishment of 2 connection-
RJ45 8-Pin
Straight Connection
I am astonished why RJ45 8-Pin connection was configured from the ...
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1answer
122 views
Is a fiber optic connection considered a “wired” connection?
https://en.wikipedia.org/wiki/IEEE_802.3
As Wikipedia says, 802.3 is for ..."wired Ethernet". How can I name copper and fiber networks in one word to describe 802.3 standard and to distinguish from ...
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1answer
48 views
How to get MAC address on same sub-network without IP [closed]
Currently I am working on a research project, let's say we have two computers connected over LAN cable directly with out any switch or router in same sub-network. Both nodes not have IP address ...
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1answer
68 views
Industrial machines lose connectivity when one is powered off
I am working with 2 identical industrial machines with multiple Ethernet switches per machine. The basic layout looks like this:
Switch 1 Machine A -> Switch 2 Machine A -> Switch 4 Machine A
...
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2answers
469 views
How many pps (64Byte each) i can receive in 1Gbps throughput modem / firewall
I need help with this:
If i have 1Gb/s throughput.
I can receive how many pps in 64Byte each packet / s?
Let's say I can send (Packet / Second - 64Byte) 450,000, meaning I would not only have 230.4 ...
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1answer
42 views
If physical switches are necessary in a SDN
Exploring how to implement a Software Defined Network and here it explains that an SDN switch is only dealing with the data layer. But then:
Do We Need Special SDN Switches for SDN Networking?
...
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2answers
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RJ45 Cable only has 4 wires
The cable that connects to my rj45 only has 4 cables, blue, orange, blue stripe, orange stripe. When I connect them to their corresponding ports, there is no internet connection.(Blue = 4, Orange = 6, ...
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3answers
109 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 ...
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1answer
44 views
Why doesn't Ethernet protocol support switch fabric topology?
While learning about Fibre Channel and SAN, I found the following information on IBM Knowledge Center:
A switched fabric is a fibre channel topology in which individual node
ports are ...
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2answers
382 views
How to connect a special device in a network
I have a question which is puzzling me.
I have a couple of custom electronic devices (are identical, one is a master and the other is a slave) which implement only up to level 2 of the ISO/OSI layer, ...
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2answers
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Practical limits of shielded Ethernet cable
If I run S/FTP Ethernet cable ran next to 120V conductors (inside 3/4" conduit) for about 70 ft. is there chance that I'll have a usable data connection? I'm fully aware that this is a terrible way to ...
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1answer
232 views
Lost Ethertype in encrypted MACsec frames
MACsec uses an Ethertype of 88E5. This presents an obvious problem when encrypting frames which already have, or should have, another Ethertype. This RedHat blog, for example, states "[MACsec] can ...
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1answer
28 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 ...
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2answers
113 views
What's the difference between Ethernet link and Serial link?
Sometimes we see router connected use Ethernet link, sometimes use Serial link, what's the difference between them? and in what scenario we use them?
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1answer
30 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 ...
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1answer
46 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-...
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1answer
115 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? ...
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1answer
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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 ...
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2answers
74 views
Does it work to use CAT6 cable between two CAT5 cables?
I have two Cat 5 cables pre-installed in the walls.
I need to connect two rooms, in which each room has its own set of in-wall Cat 5 cables and a slots.
Does it work to use a Cat 6 cable to connect ...
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1answer
41 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 ...
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3answers
134 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 ...
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1answer
243 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 ...
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3answers
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Two ports both in VLAN 1 on two separate switches down/down
For someone who recently got their CCENT, I feel kind of stumped.
I have two switches, both are Cisco 3550s. I am using VLAN 1 as a management vlan and on S1, I assigned IP address 10.24.0.11/24 to ...
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1answer
41 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 ...
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1answer
2k 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. ...
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3answers
85 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 ...
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3answers
622 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 ...
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5answers
3k views
Do network adapters read incoming bits in a single stream?
When a Gigabit network adapter is receiving data, how is it receiving the bits?
Is it seeing it all in one stream of 0's and 1's? Or is there somehow multiple streams of 0's and 1's coming in at the ...
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3answers
96 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 ...
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1answer
430 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 ...
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2answers
269 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?
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1answer
146 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 ...
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2answers
1k 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 ...
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1answer
53 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 ...
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0answers
44 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. (...
