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1500 questions
21
votes
5 answers
Why is Packet Size Limited?
I was reading: this answer to "Maximum packet size for a TCP connection", where it says:
The absolute limitation on TCP packet size is 64K (65535 bytes), but
in practicality this is far larger than the size of any packet you
will see, because the…
Algo
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21
votes
7 answers
Introductory level explanation of VLANs
What's the basic use case(s) for VLANs?
What are the basic design principles?
I'm looking for something like a two paragraph executive summary style answer so I can determine if I need to learn about VLANs to implement them.
Craig Constantine
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21
votes
5 answers
Cisco ASA site-to-site VPN failover
We recently replaced international MPLS with new ASA 5510s and site-to-site VPNs. However, when we deployed this we ran into a problem where each remote location has 2 ISPs for redundancy, but when enabling the VPN on both interfaces it flaps…
Scott Boultinghouse
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21
votes
6 answers
What is this thread-like material on this Cat6 U/UTP cable?
Does anyone know what this thread-like material to the right on the picture is?
Does it have anything to do with grounding?
It is a Cat6 U/UTP cable.
oppsig
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21
votes
4 answers
Troubleshooting "Down BGP" connections
Our network experienced a short outage when one of our BGP routes went down for a short time yesterday. Thankfully our connections failed over to our secondary BGP route after a few minutes, and the primary route became operational after a shut/no…
John Lee
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21
votes
4 answers
Risks of using non-private IP addresses internally?
My company has received a large industrial machine with many networked devices on it. Unfortunately the engineer in charge has used a public IP address range on the machine. I'm in Europe. The chosen address range belongs to a USA company. Let's say…
Transistor
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21
votes
3 answers
CEF operations on L3 switch vs router
I understand that L3 switches use CEF for faster packet forwarding. However, CEF will not work for packets that need to undergo NAT. Does this mean CEF isn't used by edge routers and edge L3 switches? Is CEF's usefulness limited to the LAN?
Michael May
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21
votes
7 answers
Building new network and need 200+ wireless devices
I'm planning the network for my company's new office space. I'm not an expert so I'd like to present my plan and ask y'all nice folk to tell me if and where I'm making mistakes.
Assumptions:
Office is 300 sq meters on a single floor with mostly…
SAR622
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20
votes
4 answers
Can I see the pending (commit at) changes on a JunOS box?
If an engineer configures some changes in a JunOS box and then set them to go live later, that effectively locks the config database with a configure exclusive. How can I see the changes that he or she has committed?
hrtednrup
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20
votes
2 answers
How can the latency value be so low from Singapore to USA (~2ms)?
Here's the ping output from Singapore:
64 bytes from 8.8.8.8: icmp_seq=1 ttl=50 time=1.96 ms
Singapore to 8.8.8.8 = ~2ms
Another ping output:
64 bytes from 23.59.8.146: icmp_seq=81 ttl=44 time=66.1 ms
Singapore to 23.59.8.146 = ~66ms
Now my…
Al Mamun
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20
votes
2 answers
What is the difference between 0.0.0.0 and a loopback IP address?
From the book Computer Network:
The IP address 0.0.0.0, the lowest address, is used by hosts when they
are being booted. It means ‘‘this network’’ or ‘‘this host.’’
... All addresses of the form 127.xx.yy.zz are reserved for loopback
testing.…
Tim
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20
votes
9 answers
Why are IP addresses given to each interface and not device? What would the implications of that be?
Why do we need to give IP addresses to each interface? Wouldn't giving one to each device be enough?
Tiago Oliveira
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20
votes
10 answers
Easily deploying new VLANs in a large environment
How do people handle the need to add VLANs to all switches on their network (or even a subset of devices)? We are adding around 6 new VLANs per week at the moment and as the network grows this is becoming a very cumbersome and risky task.
SimonJGreen
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20
votes
5 answers
Cable Colors and Purpose
I've been doing some work with some big businesses and so far I've learned yellow is internet and blue is phone.
Is this a standard or is this just a personal chose? Do colors mean different tasks?
Jason
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20
votes
5 answers
Where to cross RX/TX line in fibre optical cabling
I'm in the process of connecting together some sites via optical fibre. The trans-site multimode fibres are terminated with SC jacks on patch panels from where they are patched to the corresponding switch ports.
In order to receive a working…
user2348