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Questions tagged [ethernet]

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

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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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2answers
917 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, ...
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3answers
214 views

Access a subnet through another network

We have some devices connected together through a switch. We need to access them through another network, but because of IP counts limitation we cant get IP from that network. Q: How to access my ...
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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
20 views

How to use multiple power-lines on the same store [closed]

I have a TP-Link ethernet only power-line that works like a charm. But my needs have changed and now I want to connect two more devices, one that will work as an access point in another room and one ...
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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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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 ...
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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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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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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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2answers
12k views

Do Bluetooth Devices have MAC address with the same specification as the MAC addresses of the Ethernet and Wi-Fi Network cards?

I recently found out that ZigBee devices have MAC addresses. ZigBee is more related to Bluetooth from what I know rather than Ethernet or Wi-Fi. Do Bluetooth devices such as phones, headphones, ...
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2answers
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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
69 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
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 ...
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1answer
30 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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3answers
52k views

How does a switch learn a switch table?

Say the switch table is empty. If computer A sends a frame destined to computer B, the switch will broadcast asking who has the mac address of B. What if C suddenly sends a frame to A? What is the ...
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2answers
35 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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2answers
14k views

Role of SSAP and DSAP in Ethernet DIX frame format

I am well aware of Ethernet DIX format. But, the role of SSAP (Source Service Access Point) and DSAP (Destination Service Access Point) in IEEE802.3 Ethernet frame is confusing and always expressed ...
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2answers
14k views

Why is the ethernet payload fixed between 46 and 1500 bytes?

Can anyone explain why the ethernet payload size is fixed between 46 and 1500 bytes ? I read so many articles never get the clarification?
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3answers
280 views

Is there any reason to use a hub over a switch?

Given that hubs are essentially the same as switches, as far as I know, except they share bandwidth between all connected devices, while switches do not, resulting in faster connections. I am simply ...
34
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3answers
103k views

How does gratuitous ARP work?

Does gratuitous ARP work like a normal ARP request? Why is gratuitous ARP used for HSRP?
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0answers
13 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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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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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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3answers
259 views

Chip to Chip communication over Ethernet MDI

Does anyone have any experience with the inter-processor communication over Ethernet MDI interface. Normally, I would connect two devices with the RJ45 connectors(with RJ45 ethernet cable) and then ...
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1answer
44 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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2answers
4k views

Assign IP address using Router and Switch (DHCP)

I currently have a router and I was wondering if I could connect one of the LAN ports to a switch to connect more devices through Ethernet. I need each device to have a local IP address. I know that ...
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3answers
163 views

The recommended settings for giga ethernet connected to Ethernet port

What is the recommended duplex and speed configuration for giga ethernet port connected to legacy ethernet (10 mbps) port and there is no available duplex command available on the ethernet side? If ...
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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
12 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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89 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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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 ...
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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
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1answer
326 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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1answer
5k views

What is the difference between RJ45 connection standards WE/SS and TE-AMP and when and where are they used?

I recently decided to run some CAT6 cabling and wanted to ensure that my Crimpmaster RJ45 die would work fine for the CAT6A shielded connectors. I noticed that several people had trouble using the ...
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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 ...
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2answers
298 views

Ethernet's frame format, length or EtherType?

Ethernet defines a 2 byte header for the payload's length in its frame format. This header has an ambiguous meaning: if smaller than or equal to 1500 it represents the payload length. if ...
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1answer
58 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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2answers
4k views

How do routers traverse packets to their destination?

Sorry in advance for such a noob set of questions. I understand that when set with the task of sending a packet to its destination, a computer first checks that the IP address of the destination is ...
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1answer
9k views

Ethernet frame IG/LG bit explanation - Wireshark

I have a screenshot of an ethernet packet frame from Wireshark. I need to explain what is the meaning of these marked lines (with dots and zeros). I searched in web, but still I don't have an answer. ...
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1answer
152 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
266 views

Layer 2 ARQ protocols

Some authors (i.e. Tanenbaum, Stallings) reference ARQ protocols as layer 2 mechanisms for handling errors. Even this page from Wikipedia says that these protocols reside in the Data Link or ...
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4answers
339 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
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 ...
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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 ...
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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 %...
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2answers
124 views

What does it mean if an Ethernet Card has two RJ45 ports?

Ethernet is below IP in the OSI model. But how is an IP address actually assigned to an Ethernet port? I know, that Ethernet has nothing to do with IP, but under Windows I can assign an IP address ...
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2answers
271 views

Ethernet wiring job done wrong

I am a systems administrator by trade. Though I have done a few wiring jobs, this is not a task that I claim to be a professional at, either by training or experience. However, ethernet wiring isn't ...