61
votes
Accepted
Is Ethernet port blinking really useful?
Yes, blinkenlights are your friends! The lights can be very helpful when diagnosing problems - especially when dealing with non-managed switches or remote diagnosis with unexperienced users.
Rule of ...
- 82.7k
29
votes
Is Ethernet port blinking really useful?
My very first step in troubleshooting network issues is this:
"Are there winky-blinky lights?"
It's the network port equivalent of asking someone if their computer and/or monitor is actually ...
- 391
25
votes
Accepted
What is this device used by a networking technology company?
Connecting two fiber trunks is a tedious process. Those are splice cassettes for optical fiber - each single fiber is fusion spliced and looped into one of the cassettes for protection. Afterwards the ...
- 82.7k
17
votes
What is this device used by a networking technology company?
They're a fiber splicing crew. The white plastic trays are used to organize fiber connections.
A waterproof enclosure will protect the whole assembly from debris when their job is finished, and the ...
- 5,449
13
votes
What is the purpose of an Ethernet magnetic transformer, and how are they used?
I have been told that Ethernet magnetic transformers are used for base-t Ethernet when transmission is sent over a lengthy cable.
They are always used, not just when "sent over a lengthy cable&...
- 13.2k
13
votes
Accepted
Is there any reason to use a hub over a switch?
For the most part, no. Hubs are also known as repeaters - meaning that they basically echo whatever is coming in to a given port out all other ports in the domain. The idea is (or, more properly, ...
- 6,104
11
votes
Cumulus Linux and Whitebox switch hardware?
Disclaimer: I work at Cumulus Networks
To address a few of the high level points/concerns raised:
1.) Is ONIE getting traction?
ONIE is the de facto method for getting software onto whitebox ...
- 111
10
votes
Accepted
Why does 10Gbps ethernet claim PAM16 encoding then use a squared DSQ128 constellation?
You're talking about 10GBASE-T - most other 10G flavors use straight 64b/66b (10GBASE-R), but that doesn't work on 500 MHz Cat 6A.
With 10GBASE-T, two consecutive PAM-16 levels (on each lane) ...
- 82.7k
9
votes
Does it make sense to generally "Disable TCP Checksum Offload"?
Hardware offloading features may have bugs but they are generally beneficial. I only deactivate them on certain NICs or vendors which do have problems.
However, on a workstation/PC the network load is ...
- 82.7k
9
votes
Is Ethernet port blinking really useful?
The patterns of blinking lights on a switch can give you a quick overview of network health.
I used to work at a medium-sized company of about 100 staff, 250 PCs, a dozen servers, and the main ...
8
votes
Software Switches vs Hardware Switches
It comes down to what is accelerated through purpose-built hardware/ASICs versus what traffic flows can be punted to software/CPU for processing.
Physical switches have extremely fast switching ...
- 361
7
votes
Accepted
How to check if a NIC supports hardware timestamps
I guess you could run the command below, it will depict every capability your software and hardware networking has,
sudo ethtool -T <interface> interface information such as names are ...
- 186
7
votes
How can twinaxial cables be faster than CAT cables
Simply put, twinaxial cables allow only very short distances, under 10 meters.
And they are used in networking, for example both 40Gb and 100Gb standards support twinaxial cables... ...up to 7 ...
- 19.5k
7
votes
Accepted
Are LC-UPC connectors compatible with LC-PC?
Yes.
PC, SPC and UPC are just different polish grades of perpendicular, physical contact connectors. Their end-faces match, so they work nicely together.
In contrast, APC uses an angled surface (...
- 82.7k
6
votes
Accepted
How do hardware timestamps (hardstamps) work
The timestamping happens in hardware based on a clock in the NIC. Depending on your NIC there's either a NIC register where your timestamp will be written or some card (Intel 82580) can prepend the ...
- 1,076
6
votes
Accepted
What advances in hardware allowed DPDK to increase performance on packet processing?
I've tried to do a little research, and the most of what I've been
able to undestand is that: DPDK allows application to bypass Linux
kernel, reducing some copying and an amount of IRQ requests. ...
- 5,290
5
votes
Accepted
What certifications are there for Fiber Optic termination and splicing?
It's not terribly difficult to train yourself, if you care about the doing. If you care about selling yourself more, BICSI will happily take your money as a certifier. Probably better if you can get ...
- 2,746
4
votes
Accepted
What happens at the hardware level of a router when a packet is received and eventually triggers a process like ARP?
I'm not sure why you are stuck on ARP (Address Resolution Protocol). It is not used in receiving bits on the wire. It resolves a layer-3 address into a layer-2 address in order to build a layer-2 ...
- 98.8k
4
votes
Is there any reason to use a hub over a switch?
Hubs are bad news, from both a network performance as well as a security point of view.
As a network admin you may find it handy to have a hub or two sitting in the store for the day when you want to ...
- 2,416
4
votes
Cisco router boot error
The problem is exactly what is stated in the message you see: the nvram (non volatile ram) of your router is corrupted.
You need to change it.
It seems it is something quite easy to do, provide you ...
- 19.5k
4
votes
Accepted
CB fabric links require upgrade/training after adding New FPC in Juniper MX480
When upgrading a fabric e.g. from SCB to SCBE, there is a process to train the fabric links so they operate at higher speed. The require upgrade/training alarm is documented in the related upgrade ...
- 5,449
4
votes
Accepted
How do internet backbones (and their terminations) work?
Details will obviously vary and i'm not an expert but i'll try to answer the question from what I understand.
web browser in an Australian household laptop, and a web server in a US data centre
Data ...
- 13.2k
3
votes
Is it possible to create a collaborative network?
There are a lot of solutions on market. I would check if any of your local ISPs support line bonding. That would be ideal option.
- 1,577
3
votes
Software Switches vs Hardware Switches
The basic architecture of general purpose compute is just that - general purpose. It's great at applying significant amounts of processing power to a huge variety of workloads but it doesn't truly ...
- 6,104
3
votes
What is the purpose of an Ethernet magnetic transformer, and how are they used?
The ethernet magnetic transformer is required by the ethernet standard. You will find this question, "Why Are Ethernet/RJ45 Sockets Magnetically Coupled?" answered on the Electrical Engineering SE.
...
- 98.8k
3
votes
DLink switch loses configuration on power off!
This has just happened to me with my Dlink DGS 3120-24SI.
Apparently you need to go to the web gui then select Save ... Save Configuration / Log.
Change Type to All, then Apply.
This saves everything ...
- 31
3
votes
What advances in hardware allowed DPDK to increase performance on packet processing?
It's not just an optimization library.
DPDK is about controlling hardware functions through a framework with an Environment Abstraction Layer (EAL) that provides a general API for various device ...
- 82.7k
3
votes
Is there any reason to use a hub over a switch?
In general, no, there's no reason to use a hub over a switch, but they do still have a purpose in some special cases. One case is if you need to capture traffic to a host but the host can't run a ...
- 4,690
Only top scored, non community-wiki answers of a minimum length are eligible