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1500 questions
23
votes
1 answer

What is the practical use of a /31 CIDR or 255.255.255.254?

With a /31 subnet, we are left with zero usable hosts. The /31 subnet only has two hosts - one for network and another for broadcast. I am wondering why would someone ever use this subnet.
Bali Vinayak
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23
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2 answers

vlan 0, 1, and 4095 are reserved: what are they reserved for?

This answer says vlans 0 and 4095 are reserved. Wikipedia agrees that vlans 0 and 4095 are reserved. This article says that Cisco reserves vlan 1 (in addition to vlans 0 and 4095). But I am having trouble finding good information on what are these…
Trevor Boyd Smith
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23
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6 answers

Speed of Light in Copper VS Fiber - Why is Fiber Better?

I'm reading Computer Networks - A Systems Approach 5th ed., and I came across the following statistics for the speed of light through different mediums: Copper – 2.3 × 108 m/s Fiber – 2.0 × 108 m/s So, are these figures wrong, or is there another…
Remption
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23
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3 answers

Protocols: EIGRP vs OSPF

EIGRP and OSPF are both IGP protocols, the former is a mostly Cisco protocol and the latter is a well established open standard. What are the benefits of one over the other? Put another way, when deploying a network, why choose one over the other?…
Lucas Kauffman
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23
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10 answers

How to generate traffic for lab scenarios

I'd like to start exploring QoS, and lower level optimizations for things like broadcasts/multicasts within my home lab. I've looked around for ways to generate traffic to and from a box, but haven't found anything to really max out what a given…
A L
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22
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6 answers

What, exactly, is required to make Airplay work across VLANs?

It seems like AirPlay works out-of-the-box, vaguely speaking, only within a LAN. It's not clear to me exactly why, but it looks like at least discovery relies on broadcasts. Wikipedia states that Airplay is a proprietary protocol which probably…
alx9r
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22
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1 answer

Is a TCP server limited to 65535 clients?

There are 65535 TCP port numbers, does that mean only 65535 clients can connect to a TCP server? One might think that this places a hard limit on the number of clients that a single computer/application can maintain. One could be overseeing a web…
Kind Contributor
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22
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1 answer

How multiple client connections are made to single web server?

Actually I am learning Computer Networks and while at it, I am confused in how a web server maintains multiple connections? Simply to state, I learned trough some googling is that sockets handles a each client request. So lets say there is a web…
Sagaryal
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22
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3 answers

What is Link-local addressing?

I noticed that IPv4 reserved 169.254.0.0/16 and IPv6 reserved fe80::/10 for link-local addressing. While I saw IPv6 uses both fe80::/10 address and my private IPv6 address fd00::12 to communicate with other devices in Wireshark, I never seen…
Pue-Tsuâ
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22
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1 answer

All WiFi clients losing connectivity at the same time

In order to provide WiFi coverage for a small office area, a Cisco autonomous single-band 1041 (AIR-AP1041N-E-K9) is used, running software version 12.4.25d-JA1. The access point is having a basic configuration for a single SSID with WPA/TKIP + PSK.…
Daniel Yuste Aroca
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21
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7 answers

Minimum Ethernet Cable Length?

I have heard from a few people that cables less than 1 meter are prone to transmission problems. Is there any minimum copper cabling length? Please explain if this is true or not and share any available RFCs or standard documents. Thanks.
Jim
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21
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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
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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
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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
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3 answers

Difference between router and gateway

What is the exact difference between router and gateway? In Network configuration we set the default gateway IP address, but in reality we call the device configured with that IP address as router?
Raja
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