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1500 questions
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2 answers

Shielded Twisted Pair (STP) termination and grounding

I have knowledge terminating CAT5 UTP. But, for an installation in a remote office, the cable will be routed near a power source which we already know causes a substantial amount of 'noise' on standard telecom cables. We have purchased some CAT5e…
HaydnWVN
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Why does Ethernet use EtherType field to determine what type of packet is in a frame instead of just looking at the packet header?

I'm studying for some networking concepts and have learned that a receiving host looks at an Ethernet frame's header to determine what protocol being used by the packet. It makes me wonder though, since a packet header includes this same info, why…
ComputerWhacker
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4 answers

Difference between :: and ::1

I am confused about following netstat output. There are two kind of local ports. The first is: [::]8100 The second is: [::1]8100 I know that [::1] is a loopback address for IPv6. My question is: What does [::] mean? Thank you in advance for your…
Dadash Memmedli
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3 answers

What is the least possible separation of two NICs with the same MAC address?

Suppose you have two NICs with the same MAC address, but not necessarily the same IP address. What is the least possible separation (in terms of number of switches, routers, different IP subnets etc.) needed that would still allow traffic between…
LapplandsCohan
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13
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4 answers

How can I formulate the communication latency in TCP/IP?

I have difficulty in deriving a mathematical model/equation to estimate the round trip latency between two nodes communicating using TCP/IP. The nodes are exchanging data based on HTTP protocol. In this model, the most important factors to study are…
Espanta
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13
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6 answers

How does BGP work over TCP?

As far as I know we are using routing protocols to achieve Layer 3 connectivity, I am confused with the fact that BGP works over TCP which is L4. How can L4/TCP be established without prior L3 connectivity?
blended
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13
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1 answer

What is the 5 level QoS model (through config example)?

I have heard people stating that their network "operates a 5 level (or layer) QoS model" Sometimes they also mention a 7 level QoS model. Can anyone provide me with a Cisco IOS config example of what is meant here. So by this I mean a config…
jwbensley
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13
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2 answers

Switchport in half duplex - Download speed suffering but upload was fine

A user had issues with download speed from the Internet. The connection to the Internet is 100 Mbit/s. The user got around 7 Mbit/s downstream and around 80 Mbit/s upstream. I tested from my computer and it got around 70 Mbit/s downstream and 80…
Daniel Dib
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13
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2 answers

10GBase-T vs. SFP+ Direct Attach

What are the advantages and disadvantages of using 10GBase-T vs. SFP+ Direct Attach to interconnect devices where distance is not a determining factor?
sardean
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13
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4 answers

Hardware tap vs port mirroring - Any limitations?

I predominantly work in a Cisco environment and contemplating buying a network tap device for use with Wireshark. Can anyone provide the pros and cons from their experience between using network taps OR setting up port mirroring given considerations…
MattE
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13
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1 answer

What is the maximum prefix size routed in the IPv6 Internet?

In v4, most of the operators filter BGP updates for prefixes longer than a /24, to preserve the size of the full view. What about IPv6 ? Is there such "convention" that stands out ?
Benjamin A.
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13
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2 answers

Why does Wireshark show Version TLS 1.2 here instead of TLS 1.3?

I'm accessing TLS 1.3 test server "https://tls13.pinterjann.is" via a java http client using TLS 1.3. Everything seems to work fine as the html response indicates: What I don't understand: Why does Wireshark show in the overview Protocol TLSv1.3…
user120513
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13
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3 answers

acknowledgment by TCP does not guarantee that the data has been delivered

In RFC 793 there is a part about the acknowledgment of TCP segments: When the TCP transmits a segment containing data, it puts a copy on a retransmission queue and starts a timer; when the acknowledgment for that data is received, the segment…
kamokoba
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13
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2 answers

Is the MTU of Ethernet still 1500 Bytes?

So basically do the modern routers in the internet still use 1500 as the MTU of Ethernet? or the 1500 Byte was for the old days? What I'm asking here is what is the MTU of Ethernet in modern Networks? and if it is 1500 bytes, what will happen if we…
John P
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3 answers

How do I read optical transmit power via SNMP on Cisco ASR9k?

I am looking to read optical transmit and recieve power of XFPs in our ASR9k. The MIB used should be "CISCO-ENTITY-SENSOR-MIB" which is 1.3.6.1.4.1.9.9.91 and occording the ASR9000 documentation, this is available on…
JelmerS
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