Questions tagged [ethernet]

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

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1answer
149 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
141 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
138 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 ...
3
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2answers
301 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 ...
0
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1answer
188 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
50 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 ...
0
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4answers
288 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 ...
6
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6answers
3k views

SFP+ transceiver's ability to do 1GbE

I understand that most ports that support SFP+ transceivers can step down to allow an SFP to be plugged into it, but my question is around the transceivers/optics themselves. Can an SFP+ transceiver ...
0
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1answer
153 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
185 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 ...
4
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1answer
427 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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4answers
6k views

Why preamble is not considered a part of the Ethernet Header?

If I search where does my data start in an Ethernet frame, I get a common answer which says TCP header( 20 bytes) + IP header ( 20 bytes) + Ethernet header( SA + DA + Type) i.e 14 bytes. So, in short ...
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3answers
84 views

Two ports both in VLAN 1 on two separate switches down/down

For someone who recently got their CCENT, I feel kind of stumped. I have two switches, both are Cisco 3550s. I am using VLAN 1 as a management vlan and on S1, I assigned IP address 10.24.0.11/24 to ...
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1answer
223 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 ...
4
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1answer
2k views

Do we send ack frames in ethernet? if not then how does a router know if its neighbors are down or not?

So first off, do ethernet sends ack frames or not? if it doesn't : then how does a router know whether its neighbors are down or not? if it does : then is it cumulative ack with an ack timer or one ...
1
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1answer
447 views

How do NAT and routers work in ethernet standards?

I'm confused with how NAT and routers work in ethernet standards. In the image below, when a request is sent from Client to Server, by the time the request packets arrive R2, then what are source IPv4 ...
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2answers
301 views

Why Ethernet was chosen to be the primary protocol + why carrier ethernet was created?

I'm currently trying to investigate the extra benefit that Ethernet has to offer for the internet today. As far as i investigated & know, Ethernet gives us a new hardware, cables and functionality ...
2
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2answers
590 views

Reasons not to combine daisy chaining with path redundancy

Is there any specific (maybe obvious) reason why path redundancy and daisy chaining is not combined? Cisco does show some network topologies HERE, but the combination of path redundancy and daisy ...
2
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3answers
2k views

using fiberoptic for long-distance ethernet connection [closed]

I am trying to help provide decent (better than ATT's awful 3Mbps-on-a-good-day DSL) internet service to a cluster of homes in our rural neighborhood. The first house (near the main road) has good ...
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1answer
45 views

Category-6 cable for CCTV [closed]

T568A or T568B? Which one (1, 2, or 3)? Straight-through Cross-Over Roll-Over
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2answers
457 views

New crimped UTP cable connects and disconnects

I was just making new short UTP cables, and I was happy that when I checked the cable through an Ethernet Cable Tester, all 8 wires were straight to each other and was perfect. When I plugged the UTP ...
5
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2answers
206 views

I need the functionality of a pair of patch panels but I don't want to run one cable per port

My needs will be met by two patch panels with dedicated copper running between them for each port. But I'm looking at a few hundred ports and I'd rather not have to run a few hundred cables. ...
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3answers
1k views

Reason for excessive amount of collisions in hub networks?

I ran a test-setup which caused excessive amount of collisions on Cisco FastHub 400 port. This caused switch to isolate this port. For example in case of port 6, this has happened 766 times: Hub#sh ...
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4answers
229 views

Is ethernet a term describing just the protocol or the interfaces also?

Is ethernet describing the protocol and therefore cat5 cables became labelled ethernet cables because they are used for this protocol?
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1answer
446 views

“Overclocking” a 10BASE-T ethernet controller

What will happen if I desolder the 25 MHz clock of an ethernet module (like this one; datasheet of the chip) and add a faster clock (say 100 MHz)? The related product is a 10BASE-T ethernet module. ...
5
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1answer
153 views

Will using phone lines (RJ-11) in place of ethernet (RJ-45), in this case, be detrimental to performance?

My company has begun leasing new office space, and our modem was installed in a room without ethernet, a little ways from the router. There is a bundle of unused telephone lines (RJ-11) which run ...
4
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3answers
788 views

What practices/ mechanisms/ protocols can be used to secure communication on physically exposed Ethernet links?

Given that Ethernet cables are everywhere and use for all kinds of links and it is assumed they are physically guarded, hence typical installations do not leverage any "secure" mechanisms. Let's say ...
0
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1answer
108 views

Using home phone cabling as home network [closed]

I've just moved into a new build apartment. Each room has a female telephone port (431A?), connected to a female telephone port in my electricity cupboard. My BT telephone line then comes into the ...
5
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5answers
2k views

Why can't two hosts (in two different logical networks) connected to each other through cross-over cable communicate?

Let us say, i have two computers (hosts) A and B. Where A has been assigned an IP address of 192.168.1.10/24 and host B has been assigned an IP address of 192.168.2.11/24. And both of them has been ...
5
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3answers
4k views

Can normal CAT6 be buried? [closed]

I have the leftover from a long spool of CAT6. I'd like to run a line to my garage, which is separate from the house. Can "typical" CAT6 be directly buried, or should I buy one of the "waterproof" ...
0
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1answer
157 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? ...
12
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2answers
5k views

Is the MTU of Ethernet still 1500 Bytes?

So basically do the modern routers in the internet still use 1500 as the MTU of Ethernet? or the 1500 Byte was for the old days? What I'm asking here is what is the MTU of Ethernet in modern Networks?...
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1answer
695 views

UDP checksum calculation on improperly padded packets

Suppose I'm receiving IPv4 UDP packets whose payload is less than 18 octets, so when they are transmitted over Ethernet they have some trailing padding. Between the packets' source and my receiver ...
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2answers
1k views

How does the TCP/IP stack handle UDP checksum errors?

RFC 2460, Internet Protocol, Version 6 (IPv6) Specification, Section 8.1 Upper-Layer Checksums, states the UDP checksum is mandatory and any IPv6 receivers must discard UDP packets containing a zero ...
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1answer
65 views

sleeping computer on gigabit ethernet kills multicast performance

Problem: any sleeping computer on a gigabit network causes all multicast traffic to drop to 10Mbps. Solution: provide customers with managed gigabit switches and train them to configure the switches ...
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3answers
130 views

Gigabit NIC stuck on 100mbs

My main problem started when i installed 4 gigabit NIC into my computer. The 4 NIC are connected to GB linksys switches, each in different location,1 of the 4 gives GB and the others are stuck on 100 ...
1
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1answer
8k views

C3850 switch active/standby question

We have Cisco catalyst C3850-48T L3 switch in stack. and it is showing Active/Standby. Question: what does standby mean in stack? Does it means if i plug my laptop on standby switch port it won't ...
6
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2answers
418 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
836 views

How to tell if a Cable is Crossover or Straight from one end

So I have an ethernet cable but I can see only one end of it. From the colors this end is Straight. The other end is connected to a router or switch (I don't know where it's connected because it goes ...
2
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1answer
474 views

Difference between a bridge and just a cross over cable between two machines?

Is there a difference between a bridge and a crossover cable between two machines?
3
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1answer
5k views

Two computers connected by straight through Ethernet cable, communicating with APIPA addresses

Good day, I connected two computers together with an Ethernet straight-through cable. I did not configure any ip address, and after a while they both got APIPA addresses. Now they can ping each other ...
2
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1answer
2k views

Do flat ethernet cables perform as well as regular cables?

I came across some flat ethernet cables (like this) and was thinking of picking some up, but I have no idea if their performance would be degraded compared to regular cables. Does anyone know ...
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3answers
20k views

Why do I need a crossover cable to connect devices of the same type?

I know that a crossover cable should be used to directly connect devices of the same type and patch cable is used to connect devices of different types. But I never understood why is it so exactly? ...
0
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1answer
354 views

how to make two workstations communicate using straight through cable

Two different workstations are connected with straight through cable. Attempts to ping between hosts are unsuccessful.what should be done to make them communicate?
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2answers
271 views

What can I do with a crossover ethernet cable?

Is the file sharing of two PCs, connected with a crossover cable, both directions or only one? Would I be able to connect to a PC and play LAN games over this mini-network? Would this be extremely ...
2
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1answer
81 views

Is the patch/crossover type of cable really unimportant in a GBe network on a structured cabling with a passive switch panel?

As known, the Ethernet standard from the GBe range also prescribes the auto-detection of the cable type (in the sense of it is crossover or ordinary cable), thus there is no really need to use ...
5
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3answers
1k views

Cables on a closed rack

I've just spent the last few days building my first server rack. It will be a significant upgrade to our current mess. I was asked to buy and install one and so I did. I was not completely aware of ...
4
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2answers
320 views

Does it work to use CAT6 cable between two CAT5 cables?

I have two Cat 5 cables pre-installed in the walls. I need to connect two rooms, in which each room has its own set of in-wall Cat 5 cables and a slots. Does it work to use a Cat 6 cable to connect ...
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2answers
143 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 ...
0
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1answer
56 views

Unconnected cable in a switch

A cable plugged into a switch but unconnected on the other end, might lead to any problem in a "noisy" environment (industrial)? It's short, 50 cm, but there are motors, inverters, power supplies ...

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