Questions tagged [ethernet]

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

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PPP, Ethernet and PPPoE differences

Correct me if I'm wrong. So, Ethernet technology is being primarily used in LANs. And we use PPP in serial links. To carry IP datagram, we can use either layer 2 technology, such as Ethernet, or we ...
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1answer
42 views

Why must host A continue to transmit after host b sends runt frame post collision on ethernet? (CSMA/CD)

Trying to understand example from computer networks: a systems approach ... -Host A sends Host B a frame at time t; Packet arrives at B at time t + d; (d = one link latency) Instant before frame ...
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13 views

what does the outer conductor in coaxial cable work? [closed]

outer conductor in coaxial cable, absorb outer magnetic field or provided electromagnetic field to protect the inner conductor which carry the data signals
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300 views

Why the network switch drop the frame acording to ethertype/length?

I have a network switch IC , and I am using to the send BPDU packet. I can send packet with 2 byte ethertype/length field like this : 81 00, 80 00, 91 00 and some special hex number. But if I try to ...
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1answer
26 views

Do Cisco SG300 switches perform CRC error correction?

Cisco SG300 series switches are capable of detecting CRC errors as can be seen in the interface counters. But can they correct CRC errors and pass the frame along to the destination or the only way ...
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5answers
2k views

How does a host in one subnet know to forward the packet to the router MAC, when trying to send a packet to another subnet

I am trying to understand the ARP protocol and I could not understand the above. Consider the topology as follows: H1(1.1.1.1) - (1.1.1.0)R(2.2.2.0) - H2(2.2.2.2) My understanding is that if the ...
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2answers
285 views

MTU the most Confusing Networking term. Lot of questions

I have ton of questions and i feel this is most confusing term for me. The more i read the confusion deepens. I am not able to connect dots. please help. Do we need MTU adjustment with EoMPLS/dot1q ...
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1answer
72 views

How can 10Gbps travel over a 500mhz ethernet cable?

We recently discussed the Shannon-Harley theorem in class and compared the results between Ethernet cables to fiber optic given the same hypothetical SNR. However, it is not clear to me how you can ...
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1answer
35 views

Is it possible to upgrade a cisco 2600 series router to gigabit?

I'm new to working with networks and I have two cisco 2600 series routers (specifically 2610xm) which both have Fast Ethernet ports. I have configured these and been learning how to work with them ...
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18 views

What is wrong with this CRC calculation? [duplicate]

I have gone through a few documents to understand how to check that an ethernet frame is valid. I do the following calculation, but I can see it is incorrect because it does not result in a crc value ...
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13 views

How to perform the CRC check for an ethernet frame [duplicate]

I have an Ethernet frame of n bytes, ending with 4 bytes that contains the Frame check sequence (32 bit CRC). What calculation do I have to perform to perform the check ? I looked on the algorithm ...
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3answers
1k views

Unknown EtherType

I am parsing an ethernet dataframe. It has the form : (destination_mac_6_bytes) + (source_mac_6_bytes) + (ether_type_2_bytes). Usually, I see ethertype like Ox86dd (IPv6). But I came across this ...
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1answer
47 views

Is there any difference between International and United States patch cable?

I'm looking to buy a Cat 8 patch cable. I found a cable that I like that meets ISO/IEC 11801 Class I and Class II but it is not compliant to TIA Cat8 (As defined in ANSI/TIA-568.2-D) which has ...
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1answer
37 views

Transport layer segmentation and Ip layer fragmentation [duplicate]

From the OSI Model's point of view: If we already have Ip fragmentation which happen due to the network limitation, why the transport layer provides the segmentation mechanism via TCP protocol? why ...
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1answer
200 views

Why is default gateway in routers configuration usually set as an IP address?

I mean why not just: a MAC address? It should eliminate the need in ARP requests asking for gateway address. Also it should eliminate the need in changing IP addresses in settings when gateway IP is ...
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1answer
43 views

What is the wireless bottleneck speed in my simple network map?

My simple Network topology Im trying to figure out what the maximum speed is in mbps on the blue and red links. The exact specs of the wireless networks are these: IEEE 802.11b/g/n, 2.4GHz Dual ...
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2answers
446 views

Is a datagram from an upper network layer converted 1:1 to one of the lower layer?

I know datagrams from upper layers are converted to those of lower layers by adding metadata, but I cannot seem to find this information anywhere. Which one of the below is correct? A single TCP ...
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1answer
36 views

Enterprise network VS Industrial network [closed]

I would like to know the difference between the enterprise network and industrial Network.If someone has experience in industrial network, is he able to work in enterprise network?
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1answer
53 views

Why is XGMII little endian while the network is in big endian?

Why is XGMII little endian while the network byte order is big endian (RFC1700)?
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1answer
43 views

Crossover Cabling - Reversing TX and RX Signals [duplicate]

It is often said that crossover cables 'reverse the transmit and receive signals' compared to straight through cables. However I am yet to see an actual explanation of why the reversal of signals is ...
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2answers
144 views

Industrial Ethernet network design

looking for some advice on network architecture for an industrial switchroom with several constraints. Modbus TCP devices are located in motor control centre cells, these need to connect to the ...
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121 views

How does a Hub work when sending broadcast packages?

I know that hubs send broadcast packets, so every packets is received by each node in the broadcast domain. I read that frames that are received but that aren't addressed to a NIC'S MAC address are ...
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1answer
53 views

SFP to RJ45 for 10Gbit network

I am in the process of upgrading some of our network into 10Gb and grabbed the following: A network switch by netgear, mode:GS110EMX A bunch of assorted cat8 cables(for future proofing) Two 10gtek ...
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81 views

Can / Is CSMA/CA used in wired network?

I learnt why CSMA/CD cannot be used in wireless protocols here. Here is what the answer says: Wireless transceivers can't send and receive on the same channel at the same time, so they can't detect ...
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56 views

understanding fiber optics layers architecture

I'm studying the history and technical details about fiber optics and I'm having trouble understanding which are the different layers that exist and have been used over fiber optics. For example, I ...
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1answer
55 views

GPON upstream frames capture

How capture GPON upstream traffic ? Some professional tools exist: GPON doctor, GPON Xpert, displaying the GPON frames, etc, but is it possible to perform this task without using these tools ? My ...
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1answer
97 views

Get the raw binary stream from an optical fiber

How get the raw binary stream from a fiber ? Assuming we have a SFP (ethernet, FC, GPON, other), this transceiver is not protocol independant, and will treat and interpret the binary stream received ...
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83 views

What happens to undetected Ethernet errors?

The checksum used in Ethernet packets cannot 100% detect errors. If that is the case, how can I ensure that some file I have transferred from one computer to another is uncorrupted? Thanks
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1answer
144 views

Is PPP a useful choice for fiber connections?

I was recently thinking about how I would go about connecting two separate buildings using optical fiber cables. This is mostly for understanding how this would be done to further my mental horizon, ...
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1answer
48 views

Is it possible to propagate MAC address back to sender?

Let me first to tell me what I know, please correct me if I am wrong. I know when Ethernet frame travels across the internet then Layer 3 data (Source and Destination IP) remains same and Layer 2 ...
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2answers
112 views

How is Ethernet a packet-switched network?

Let's say for example there is an Ethernet switch, and there are four PCs connected to this switch. PC1 and PC2 are communicating with each other, and at the same time PC3 and PC4 are also ...
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1answer
62 views

Is it possible to use a gigabit connection on 10/100 load balancer?

My ISP provides a connection output of 1000BASE-T. I am trying to feed this to a load balancer device that only supports a 10/100 connection. However, the connection is not detected. I am afraid this ...
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3answers
239 views

MSTP Ring - Maximum Number Of Switches?

We have inherited a ring topology with 12 switches configured with MSTP. Each switch is either 4 or 8 ports but in general most are 4 port with 2 fiber uplinks that form the ring. We are getting a ...
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1answer
43 views

Inital value for the scrambler in 10GBASE-R

The standard says "There is no requirement on the initial value for the scrambler. The scrambler is run continuously on all payload bits". I'm curious how the scrambled data can be recovered. To my ...
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Why wifi and ethernet use the same frame format from tcpdump -d output?

If I execute tcpdump -i wlan0 tcp -d or tcpdump -i eth0 tcp -d I get the same output (000) ldh [12] (001) jeq #0x86dd jt 2 jf 7 (002) ldb [20] (003) jeq #0x6 ...
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1answer
95 views

Scaling fragment offset

I studied that fragment offset has 13 bits. At transport layer segmentation is done considering the the MTU at lower layers (network layer, data link layer). Ethernet format says the maximum data ...
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2answers
146 views

Can you stack Cisco 350 28P PoE switches with CAT5E or CAT6 ethernet cables?

I have four new Cisco SG 350 28P PoE switches, but no stacking cables. Can I use CAT5E or CAT6 ethernet cables to accomplish stacking them?
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47 views

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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82 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
1k 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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72 views

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
138 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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2answers
596 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
208 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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336 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
179 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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1answer
229 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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3answers
3k 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
440 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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