Questions tagged [ethernet]

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

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Why do all leaf nodes in an E-Tree service belong in the same subnet?

I'm studying the CCNA R&S at the moment and I'm a bit confused about why E-Tree services require all leaf nodes to belong in the same subnet, despite the leaves only being able to send layer 2 ...
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2answers
61 views

Is Spanning Tree Protocol Needed?

If there are two switches connected directly together with two links is spanning tree protocol needed? please see below snippet
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1answer
37 views

Broadcast link vs. point-to-point links

What is the distinction between broadcast links and point-to-point links? In the paragraph below, the author switches between "broadcast link" and "broadcast network" which is causing my confusion..is ...
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2answers
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Internet Entry Point

I am learning netwroking and would like to ask about how exactly we (as a casual user) get connected to internet and how a datacenter would do the same thing. i bet they dont use a regular modem which ...
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1answer
50 views

Sending TCP packet to the other device without connection

I think the sending packet to other device works like the following. 1. The server device listens with port. for example 80 2. The client connects to the server devices. for example, the port of ...
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1answer
44 views

What exactly is fragment free switching?

Most commonly refered to as a compromise between store-and-forward and cut-through switching, this method involves storing the first 64 bytes of the ethernet frame in a buffer and then forwarding it. ...
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2answers
92 views

Which physical layers are part of PROFINET?

I understand that Profinet builds on Ethernet, but I am not quite sure how. Ethernet has a lot of different standards for the physical layer, eg 10Base2 (coaxial, 10 Mbit/s), 100Base-TX (twisted ...
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2answers
49 views

Confusions regarding byte and bit ordering of Ethernet Frame

I understand the concept of Endianess regarding numbers because there the bit significance is well defined. But when applied to things like Ethernet frame or Mac address, things are so clear to me, ...
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3answers
9k views

What is “industrial ethernet”?

When a teacher introduced it to us he gave the impression that it specifically covers some Siemens technology; that it's even a Siemens trademark. I believe the term covers something more general, ...
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1answer
62 views

Weird Wireshark protocol list (eth:ethertype:ip:data where is the “udp”?)

I am capturing incoming and outgoing WAN to LAN data at a particular host on my LAN (i.e., the one actually receiving/sending the data). Sometimes I get anomalous captured frames that are missing the ...
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25 views

Wireshark logging same error on client and server

I did some testing in Socket Programming with JAVA and analyzed my traffic with wireshark. SetUp: 1 Server running a new ServerSocket(PORT) and 1 Client running a new Socket(IP, PORT). Server and ...
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1answer
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How 2 devices with different speeds communicate [duplicate]

This is an extremely basic question, But I couldn't find any answer for that. In the scenario which I have a very old compubter that transmits 10Mbits/s and a switch that has 100Mbits ports, how ...
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1answer
61 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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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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26 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 ...
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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
56 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, ...
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1answer
78 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 ...
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1answer
42 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 ...
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1answer
56 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 ...
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2answers
41 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 ...
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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
21 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
36 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, ...
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1answer
104 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
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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
40 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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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 ...
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0answers
137 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 ...
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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 ...
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1answer
378 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
77 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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1answer
81 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
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 ...
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1answer
63 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
192 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
49 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
110 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
60 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
349 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
56 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
67 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
130 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
60 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
105 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
573 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
78 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? ...