Questions tagged [ethernet]
For questions relating to Ethernet networking, as defined by the IEEE 802.3 standards.
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1answer
39 views
Cisco nexus 9396PX TX output discard on 40G interface without link congestion
We have cisco nexus 9396PX with N9K-M12PQ module (12x40G Interface), We have 8x10G L3 LACP bonded connectivity with our ISP and so far so good no issue at all. but recently we migrated that LACP LAg ...
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0answers
12 views
Is pair cable always full duplex? Can it be half duplex at double the bitrate? [duplicate]
This is probably a newb question, forgive me.
For pair cable, there are two signals that can be sent: following that logic, it seems like you could have two situations: full duplex at bit rate X in ...
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0answers
24 views
Expanding network to attached building
I own a electronic design company, and recently moved into a new office space. We currently are setup in the front office, location "1" on my image. We also are converting a warehouse into an assembly ...
6
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3answers
2k views
Why can a packet sniffer in an Ethernet LAN obtain all packets sent over the LAN?
Why can a packet sniffer in an Ethernet LAN obtain all packets sent over the LAN?
In a limited broadcast environment, such as in many Ethernet LANs, a packet sniffer can obtain all packets sent ...
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2answers
31 views
What all fields is the FCS/CRC in the trailer of the ethernet frame calculated over?
I am unable to find the correct answer to this question all over the web. Wikipedia states The FCS value is computed as a function of the protected MAC frame fields: source and destination address, ...
2
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1answer
71 views
Using an Ethernet cable and USB Ethernet adapter at the same time?
What would happen on using an Ethernet cable connected to one network and
then plugging in another Ethernet cable but using an USB Ethernet adapter from a
different network.
Would it connect to both ...
1
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1answer
33 views
RS_FEC OVERHEADS ON 25GBASE-R
I'd like to estimate the effective capacity of the 25 GbE link (25GBASE-R) to transfer an Ethernet payload of a particular size when Reed-Solomon RS(528,544) forward error correction (RS-FEC) is ...
0
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1answer
32 views
How does Kismet find WIRED devices when scanning Wi-Fi? [closed]
In an effort to better secure my Wi-Fi network by finding its weaknesses and mitigating them, I have employed the use of Kismet, a well known Wi-Fi security scanning tool. When I use Kismet to scan ...
2
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2answers
37 views
Circuitry for sending and receiving bit streams in networking
To my little knowledge , I know that digital signals are transferred over continuous EM signals . At the receiver end a bit 1 is detected when the amplitude crosses a certain threshold and a bit 0 is ...
0
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1answer
70 views
Is there a MTBF related to port linking?
During a firmware upgrade, I've noticed one problem: An equipment keeps linking/unlinking on a specific port of a PowerConnect 3548(stp portfast, switchport access mode). I've contacted the local ...
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0answers
14 views
Wago 750-377 - assign IP address
I've just bought a 750-377 wago fieldbus coupler and I'm trying to assign an IP address to it through an ethernet cable that goes from the device to my computer. Is there any way to do that or do I ...
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2answers
33 views
what does the flag and mtu means in here
Reading some logs from my system it states
eth0: flags 4163 < up, broadcast, running, multicast> mtu
I am not sure what is the meaning of the flag here
down below I see eth1,2,3 has the same flag ...
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8answers
3k views
What do the positive and negative (+/-) transmit and receive pins mean on Ethernet cables?
So I'm trying to understand the pin layout of an Ethernet port, specifically for 8P8C which to my understanding is the most common. Of the eight pins, only four are apparently used for communication, ...
0
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1answer
47 views
What is the use of Phy and MAC chip?
Is it mandatory to have a MAC and PHY chip?
Are these two chips within a NIC CARD?
As I understand, these two chips are connected using RGMII or SGMII or xaui.
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5answers
3k views
How exactly does an Ethernet collision happen in the cable, since nodes use different circuits for Tx and Rx?
I am trying to understand how a collision occurs in Ethernet, especially when a duplex mismatch exists or when on a legacy Ethernet network two nodes transmit simultaneously.
Everyone explains the ...
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1answer
39 views
MAc address or IP address? which one gets used from my pc to router? [duplicate]
Question 1) which one is used nowadays? NAT or PAT?
Question 2) as I knew, when my pc requests some website, what happens is , the data(packets) from my pc go to router. then router makes the request ...
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0answers
9 views
What happens within a switch when a frame is moved from Device A on Switch 1 to Device B on Switch 2? [duplicate]
This might be a noob question but what happens within a switch (regarding mac tables) when a frame is moved from Device A on Switch 1 to Device B on Switch 2? I'm assuming the 2 switches are connected ...
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0answers
13 views
Ethernet Frame: Length Field and Transceiver [duplicate]
I saw the following description of an ethernet frame:
8 bytes: preamble & start-of-frame delimiter
Variable size data: 42-1500 bytes
– No length field: the transceiver grabs the ...
0
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0answers
93 views
How Cisco Line Protocol works
How do Cisco Line Protocol works ?
I could read this: https://www.cisco.com/c/en/us/support/docs/content-networking/keepalives/118390-technote-keepalive-00.html, about Ethernet Interfaces keepalive ...
6
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2answers
2k views
Why maximum length of IP, TCP, UDP packet is not suit?
From many tutorials, I get follow knowledge(maybe I'm misunderstood) :
maximum of an Ethernet packet is about 1500 bytes.
maximum of an IP packet is about 65535 bytes.
maximum of a UDP packet is ...
3
votes
1answer
330 views
What does MTU depend on?
I'm trying to understand what factors determine the MTU. For instance, why 802.11 has MTU of 2304 while Ethernet MTU of 1500? Are there restrictions of the physical medium or arbitrary design ...
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2answers
53 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 ...
0
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1answer
60 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 ...
42
votes
5answers
13k 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 ...
0
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1answer
48 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 ...
4
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1answer
156 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-...
1
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1answer
48 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 ...
3
votes
1answer
104 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 ...
0
votes
1answer
51 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 %...
2
votes
4answers
340 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 ...
0
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1answer
54 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
47 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
52 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 ...
0
votes
1answer
127 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
55 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 ...
5
votes
1answer
78 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
...
3
votes
2answers
536 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 ...
0
votes
1answer
65 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?
...
1
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2answers
990 views
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, ...
4
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3answers
149 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 ...
0
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1answer
55 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 ...
6
votes
2answers
399 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, ...
1
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2answers
105 views
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 ...
4
votes
1answer
265 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 ...
3
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2answers
271 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?
1
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1answer
32 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 ...
1
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1answer
89 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
184 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? ...
1
vote
1answer
60 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 ...
