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1500 questions
262
votes
6 answers
The slash after an IP Address - CIDR Notation
What does /16 mean in 192.168.0.0/16 ?
4m1nh4j1
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185
votes
9 answers
Why do we need a 3-way handshake? Why not just 2-way?
The TCP 3-way handshake works like this:
Client ------SYN-----> Server
Client <---ACK/SYN---- Server
Client ------ACK-----> Server
Why not just this?
Client ------SYN-----> Server
Client <-----ACK------ Server
smwikipedia
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137
votes
6 answers
How do you calculate the prefix, network, subnet, and host numbers?
Example:
IP: 128.42.5.4
In binary: 10000000 00101010 00000101 00000100
Subnet: 255.255.248.0
How could you determine the prefix, network, subnet, and host numbers?
user5032
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95
votes
12 answers
IPv6 address space layout best practices
I'm comfortable with IPv4 address space allocations. By which I mean: Given services to plan for, or an organization to network, I have a good grasp of how to plan IP address space usage. (or at least, I think I do. :)
Are there any best practices…
Craig Constantine
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86
votes
21 answers
When to choose fiber instead of twisted pair (copper)
These days both fibre and twisted pair are supporting 1000BASE-T and 10GBASE-T, but when do you choose one over the other? The obvious one is maximum cable length, but what are other factors which might come to mind when making this choice.
Lucas Kauffman
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86
votes
4 answers
Why and how are Ethernet Vlans tagged?
I hear about VLAN tagging, but I don’t quite understand the concept. I know a trunk cannot accept untagged packets without configuring a native VLAN, and that access ports only accept untagged packets. But I don’t understand why packets need to…
Vishwanath gowda k
- 1,079
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81
votes
4 answers
What's the difference between IKE and ISAKMP?
I've been building IPsec VPNs for years but to be honest I've never fully grasped the technical difference between IKE and ISAKMP. I often see the two terms used interchangeably (probably incorrectly).
I understand the two basic phases of IPsec and…
Jeremy Stretch
- 4,728
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79
votes
5 answers
Ping port number?
Yesterday an interviewer asked me what the port number for ping is and which protocol ping uses: TCP or UDP.
After the interview, I searched on the Internet and found different results: someone says ICMP uses port 7, someone says it does not use any…
Nishad Morey
- 1,364
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74
votes
5 answers
Why are IPv4 addresses running out?
I understand that we are running out (or ran out already?) of IPv4 addresses, but I don't really understand why that is. Right now, every home has its own IPv4 address (dynamically assigned, but still, each has an address). Why can't a city (for…
mnj
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73
votes
5 answers
Is "IPv10" a joke or a serious RFC draft?
Internet Protocol version 10 (IPv10) Specification
The name is funny (IPv4 + IPv6 == IPv10), but the actual proposal looks strange (one more packet format to battle incompatibility between packet formats).
Is it a normal proposal that have balanced…
Vi.
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67
votes
6 answers
What is the meaning / origin of the terms north-south and east-west traffic?
In context of networking I keep running into statements such as "east-west traffic is larger than north-south traffic". I have tried a bit of googling but have not been able to locate an authoritative answer to understand the origin of these…
ams
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62
votes
9 answers
Is 30 Mbit/s fibre for WAN faster than 30 Mbit/s copper?
A network engineer professional is overseeing our town's installation of fibre and was explaining how much faster it was.
I pointed out that it wasn't a silver bullet as you had to pay the provider for a certain bandwidth. For example, I explained,…
wcndave
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61
votes
10 answers
Why only port 80 for web services?
Why isn't it sensible to dedicate more than one TCP/IP port to http? Although admittedly naive, isn't it intuitive to think that server performance could somehow be increased?
Marcos Gonzalez
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57
votes
14 answers
Multi-Mode and Single-Mode Fiber Differences
When cabling a network using fibre, what is the difference between single-mode and multi-mode fibre? When should I be using one or the other? Are there compatibility and/or speed concerns with either?
mdpc
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56
votes
10 answers
Reason for both a MAC and an IP address
If my computer has an IP address,why does it need a MAC address?
user1369975
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