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1500 questions
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3 answers

Are the IPv6 address space and IPv4 address space completely disjoint?

Tanenbaum's Computer Networks says Finally, IPv4 addresses can be written as a pair of colons and an old dotted decimal number, for example: ::192.31.20.46 Does it mean the IPv4 address space is embedded into the lowest subrange of the IPv6…
Tim
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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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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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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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13
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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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How does a packet get corrupted in a network?

I recently read about CRC, a checksum to detect package corruption and drop corrupted packages. But how does a packet in an IP-based network get corrupted in the first place?
Tehmas
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RIB vs FIB differences?

Can someone explain the differences between a RIB and FIB a little further? I didn't see any similar questions on the site so I thought this would be a good addition. The RIB routes and the FIB forwards? Is that all there is to it?
stets
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Detecting different Ethernet frames

How can someone distinguish between different packets in the Ethernet protocol? It has no "length" field/area as higher-level protocols use to do so. Because this protocol has handling in both the physical and the logical scopes, I assume that the…
Reflection
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Why does OSPF need Type2 LSAs?

Learning more about OSPF for CCNP studies. I'm looking at how OSPF builds its links, and have just covered Type1 LSAs. Looking at Type1 LSAs, I'm wondering why these are even necessary? The book I'm reading implies that Type2 LSAs are used to…
A L
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Can a router send ARP requests to hosts?

I play with libpcap in C recently to create an arp sniffer program that captures arp requests on the air. I came up with a strange effect. I captured arp requests from my router. I don't know if this is a bug of my program, but I was curious (even…
user33076
13
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5 answers

What IPv6 prefixes should never be routed?

Seems clear to me that the Link Local, and Unique Local, addresses should at least be filtered. Is there anything other than LLA/ULA that should be filtered? For LLA, is it standard practice to blanket filter the full fe80::/10, or just filter the…
Craig Constantine
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4 answers

MTU and Fragmentation

Consider the following: NAS with 10G interface connected to 10G interface on switch. Client computers connected to switch via gigabit Ethernet. Will there be any gain in performance if MTU size is increased on NAS and switch port to which NAS is…
sardean
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13
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6 answers

Why do I need to specify a subnet mask on interface?

When assigning an IP address to an interface, why do I need to specify a subnet mask? I understand the purpose of subnet masks in a routing table for example (to specify a range of IP addresses as destination). But why is it necessary on an…
Gradient
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netstat -nr returning "0/1" -- what does that mean?

In exploring how my local openVPN virtual interface utun0 works, I came across the following data, and I don't know how to make sense of it. (I'm on a Mac) $ netstat -nr Routing tables Internet: Destination Gateway Flags …
Alexander Bird
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