Network Engineering Stack Exchange
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1500 questions
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
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4 answers

What does a UDP connection timeout really mean?

Since UDP is a connectionless protocol, I'm confused by the setting on my Sonicwall Firewall for "UDP Connection Timeout". It's set at a default of 30 seconds -- but what exactly times out after 30 seconds? Here's my actual real-world situation: I…
Jon Wadsworth
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21
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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
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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
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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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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
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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
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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
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2 answers

Is it common for ISPs to connect to each other directly?

I'm reading up on the relationship between latency and ISP interconnectivity (that higher ISP interconnectivity results in lower latency, which makes sense to me). My understanding is that IXPs provide the primary means of ISPs to connect with each…
Zach Smith
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20
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4 answers

Why is the CAM table in a switch called CAM table and not MAC table even though it holds MAC addresses?

I know the CAM table in a switch holds MAC addresses and the ports that are associated with the respective MAC addresses. There are no such thing as CAM addresses from my knowledge, so why is it called CAM table and not MAC table?
yoyo_fun
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20
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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
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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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20
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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
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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
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