Questions tagged [ethernet]

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

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Minimum MTU size on Ethernet and minimum Ethernet frame size

I am a bit confused about the understanding of the relationship between minimum MTU of MTU and minimum Ethernet frame size. We know that the maximum MTU of Ethernet is 1500 Bytes which makes the ...
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Will one ethernet cable do or should I install two or three…? [closed]

I have two cctv cameras, a tv and my desktop pc that I want to connect to the router about 20m away by ethernet. Will a single cable do with an unmanaged switch or should I install two or even more. ...
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1answer
21 views

Which type of ethernet cable for external runs to cameras and home office? [closed]

I'm sure this question has been asked a hundred different ways, but I've been struggling to piece the various bits of information together and finding quite a lot of misinformation about ethernet ...
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Optical RX/TX only link [duplicate]

If I connect on one side only TX (RX stays empty in the optical LC Transceiver) and on the other only RX (empty TX) will the link come up ? Both sides are ports on a switch. I assume the RX side comes ...
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How strong a ground loop would necessitate the use of isolation transformer in Ethernet? [closed]

One reason against the use of shielded twisted pairs in residential environment is the possibility to create a group loop between equipments, as discussed in Shielded Twisted Pair (STP) termination ...
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7 views

ARRIS CM820S modem and WiFi [closed]

this if my first post on this stack! I've recently moved in a flat to see an Arris CM820S modem, which is working fine when i connect it directly to the PC using standard RJ45 cable, which is the only ...
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0answers
11 views

Arduino parses UDP packets through Ethernet with gibberish in it [closed]

Arduino Yun (with built-in Ethernet) is connected to a PC (through Ethernet) which is connected (through WiFi) to my router. Is set to receive UDP packets from another PC (on the same network). That ...
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32 views

CAT 5 cables work, but CAT 6 doesn't? [closed]

My setup is, Router - CAT 5 cable - CAT 6 rated wall socket - CAT 6 cable - CAT 6 rated wall socket - CAT 5 cable - PC This works fine but the speed is limited. When I replace the CAT 5 cables with ...
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21 views

Cant access wireless devices from a wired device [closed]

I have a ZTE F660 router provided by the ISP. My PC is connected through wire/ethernet cable to the router. Recently I was tinkering with a microcontroller known as ESP 8266 commonly used for simple ...
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6answers
2k views

Why can't we create a hierarchy of hubs?

I was reading the Comptia Network+ All in One book and I came to know that we cannot create a hierarchy of hubs. My question is why so? Are MDIX ports simplex? Why is it not possible for the hubs to ...
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14 views

Juniper MX - ERPS over MPLS CCC or VPLS

I wonder if there is a possibility to implement an ERPS Ring over a few Juniper MX nodes that are interconnected via MPLS only? The only idea i have to configure this is using lt - interfaces with a ...
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1answer
42 views

What clear substance could be sprayed on RJ45 Ethernet terminals? [closed]

As installed by Verizon, the cat5e/cat6 cable does not plug directly into the Ethernet port of the unit. Instead, there are terminals for each wire pair (see photo). If one were to open the snap-close ...
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2answers
36 views

How do routers. switches, bridges and hubs deal with corrupted data?

By data corruption I mean frame/packet corruption, we can stick to the corruption due to a collision for simplicity. I know that switches can detect frame corruption if they are not set to cut-...
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2answers
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why ip protocol use fragment offset instead of index number?

I was wondering why the IP protocol use fragment offset to define the fragments of an IP datagram instead of using index number (first fragment with index 0, second with index 1, ...). We already know ...
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using SNAP/ LLC on ethernet

Why is it not desirable to use Logical Link Control (LLC) and Sub-Network Access Protocol (SNAP) on Ethernet 802.3 frames while carrying IP packets when it is often used for wireless networks?
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Can computers connected within a Network via Ethernet monitor access the information uploaded/downloaded on a different computer

Suppose there are many computers connected within a Network. Let's take 2 examples. Computer A and Computer B, connected within the same network. Suppose, At the start of the day, say myself as an ...
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2answers
49 views

Why do WiFi bridges replace the source MAC Address with their own?

Ive read quite a bit about the issues i currently have with my Aruba WiFi Bridge 501 and the failure of DHCP going through, and as far as i can tell the issue is that the bridge replaces the MAC of ...
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Can the interface types otnOtu, otnOdu and opticalChannel have metrics such as ifInDiscards, ifOutDiscards?

In my understanding, the metrics "ifInDiscards", "ifOutDiscards", "ifOutErrors", "ifInErrors", "ifOutUcastPkts", "ifInUcastPkts".,,,etc are basically related to the interfaceType ethernetCsmacd. Can ...
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1answer
34 views

How does the Ethernet handles start of frame collision?

The Ethernet preamble, 56 bits of alternating 1 and 0 bits, allowing the receiver to synchronize its clock to the transmitter, followed by a one-octet start frame delimiter byte (10101011) and then ...
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1answer
101 views

what's the difference between trailer and padding field in ethernet frame captured by wireshark?

The Ethernet minimum length should be 64 Bytes, so when the data is less than 46B, there would be some extra bytes padding to the end of data, make sure the frame size up to 64B. When I capture the ...
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2answers
65 views

What is an acceptable bit error ratio?

I recently got a job in IT infrastructure and terminating Cat5e is something relatively new to me. What is an acceptable bit error rate for 1 million packets? Here is a screenshot of a test I ...
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1answer
31 views

What is ethernet length/type 0x9104

While capturing packets on my Raspberry Pi via my Wireshark tap (sudo tcpdump -i eth0 -w - > tcpdump.data) between my MacBook Pro and eero base station on ethernet, not wifi, the following packet ...
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4answers
365 views

Layering unicast addressing over multicasts

My question has to do with layering of unicast over multicast and has two parts. Part 1. IP unicast over MAC multicast First part of the question is whether there is a standard that prohibits use of ...
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2answers
2k views

Why does Ethernet use EtherType field to determine what type of packet is in a frame instead of just looking at the packet header?

I'm studying for some networking concepts and have learned that a receiving host looks at an Ethernet frame's header to determine what protocol being used by the packet. It makes me wonder though, ...
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1answer
21 views

Direct connection betwen two Ethernet-to-wifi adapters [closed]

I currently have two computers connected via ethernet and a switch, using static ip-addresses. I would like to connect a third computer, this time wirelessly. And I am wondering whether the setup in ...
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3answers
498 views

If no CSMA/CD on switches what are they using

As far as I understand, CSMA/CD is an access method to place Ethernet frames on the wires in computer networks. I read everywhere that switches are not using this access method because they are full-...
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1answer
32 views

How does a 802.11 (wifi) frame identify the payload's layer 3 protocol?

My understanding is that the 802.11 frame header is an equivalent of ether header. In the ether header, there is an EtherType field that identifies the payload protocol, such as IPv4/IPv6/ARP etc. ...
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3answers
129 views

Clarification on when routers encapsulate and decapsulate packets

I'm an application developer working on getting a working knowledge of network engineering, so basically a newbie. I've been trying to figure out exactly when routers decapsulate frames into packets ...
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3answers
53 views

setting up a VLAN and joining 2 buildings through underground cabling

I am pretty much a newbie when it comes to networks so forgive me in advance if this question seems odd. So here's a situation I am trying to figure out. There's a company who operates in 2 adjacent ...
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2answers
47 views

Are optical Gigabit SFP modules backwards compatible with 100Base-Fx?

My FTTH connection is using an old CareLink CL-MC-W2B-20-100 optical converter. It is labelled: 10/100 Base-T to 100Base-Fx bi-direction/single fiber media converter 10/100M Single mode WDM 20Km ...
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Manually break ethernet frames [closed]

i have the next question: how can i manually create interference in fast ethernet cable or download the special program which will randomly corrupt ethernet frames (OS is not important)?
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1answer
38 views

Ethernet Link Status when when Autonegotitation is enabled

I'm trying to understand when a 10Base-T / 100Base-T Ethernet PHY device will signal a valid link, specifically by setting the Link Status bit in the Status register, in cases where autonegotiation is ...
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Switch Operation Beyond VLAN Segmentation

What are the other operations performed by a switch which are outside the VLAN's boundaries. Is Logical (VLAN) Segregation is exactly same as breaking a switching network physically via a Router?
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Timing in Virtual Links for Ethernet

From my understanding, full duplexed switched ethernet networks provide determinism. However, the Bandwidth Allocation Gap does not define a time schedule 2 virtual links could have frames ...
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2answers
471 views

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
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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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2answers
348 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
50 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
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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
451 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
87 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
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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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23 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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19 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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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
69 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
67 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
204 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
58 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
464 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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