Questions tagged [ipv4]

For questions about Internet Protocol version 4 (IPv4); as specified in RFC791.

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IPv4 depletion and suggested solution [duplicate]

An IPv4 address is 32 bit long, which would give us the total of 4 294 967 296 addresses. when they realised that this IPv4 may not be enough, was it possible to just add maybe another 8 bits to the ...
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37 views

How can someone connect to my computer even through port forwarding?

If I set port forwarding up on my router to redirect connections on port, say, 50000 to my computer, how can someone connect to my router in the first place ? Does that mean that my router has a ...
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How can I use scapy to make a port appear open-device behind NAT?

This has been asked in stack overflow like 7 years back. I don't see the correct answer there. Is there any way to do this? While this packet keeps on being transmitting, doesn't the other end see the ...
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1answer
32 views

How does a packet know where its destination is? [duplicate]

When I connect to my friend's mobile Wi-Fi hotspot, we both have the same public IP address. Now, when I go to duck.com, how does DuckDuckGo know where to deliver the packets? I mean, I and my friend ...
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1answer
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Duplicate IP addresses on different "levels" of subnets

My question is quite simple: let us say there is a 10.0.0.0/8 with the subnet mask of 255.0.0.0 (first 8 bits used up for network address). Let us say, one address in our subnet is 10.0.0.1 (subnet ...
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46 views

What is the reason behind not returning unused IP addresses? [closed]

There are several companies out there with one or more /8 IP addresses, for example: DoD has more than 200 million, HP has one /8 (>16 million), Apple has one /8, General Electric has one /8, IBM ...
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5answers
202 views

What happens to the unused IP addresses in the subnet that falls in between two routers?

This is probably a un-realistic question, but a question nonetheless, that has been bugging me since quite a while now. Consider the below network diagram, where R1 is a part of a 10.0.0.0/8 network (...
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Really new to Networking and wondering how the first 3 octets of 255 is 1 network [duplicate]

Watching this video on subnetting and I am kind of confused as to why the first 3 octets are all counted as one network but the last octet only adding 1 bit to it makes another network entierly. I'm ...
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What is the minimum MTU of IPv4 68 bytes or 576 bytes?

I read that 68 bytes is the minimum size of IPv4 datagram every device must be able to forward without further fragmentation. 576 bytes is the minimum size of IPv4 datagram every device has to be able ...
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1answer
552 views

Which one right, UDP has 508 or 512 bytes payload limits?

We know the size guarantees the datagram won't be fragmented in IPv4 is maximum 576 bytes. But the size when use UDP header 8 bytes and if we take UDP payload 512 bytes and choose maximum header size ...
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network IP packet format

i completely understand that why receiver there is 576 bytes but my question is as technology update every after one Minutes then why we can't update that limit [enter link description here][1]
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Do IPv6 addresses have better persistence with DHCPv6?

I have a LAN with about 25 devices that occasionally grab each other's IP address via DHCPv4. I know there are certain lease time limits and it can be set to very long periods to work it around to an ...
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Are IPv4 type of service and IPv6 traffic class equivalent to each other or is traffic class IPv6 specific? [duplicate]

IPv6 has a traffic class field. According to the specification it is an IPv6 length, out of which first 6 bits are called code point or differential services code point (DSCP) and the last 2 bits are ...
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1answer
101 views

How to tell if an ipv4 address is public or private?

I've read the below thing, in a website. According to standards set forth in Internet Engineering Task Force (IETF) document RFC-1918 , the following IPv4 address ranges are reserved by the IANA for ...
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1answer
73 views

Why the pseudo-header is not transmitted with the UDP datagram?

I have read from E. Comer - Internetworking with TCP/IP 4th edition that "The purpose of using a pseudo-header is to verify that the UDP datagram has reached its correct destination. The key to ...
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1answer
57 views

UDP checksum calculation for checksum results in the value zero

I read UDP checksum from Wikipedia that "If the checksum calculation results in the value zero (all 16 bits 0) it should be sent as the one's complement (all 1s) as a zero-value checksum ...
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1answer
68 views

Why UDP checksum is optional for IPv4?

We know that IPv4 header has checksum for header not for data .Therefore for checking data error we need checksum in transport layer. Suppose we're using UDP in layer 4. So if I remove the checksum ...
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1answer
47 views

How UDP checksum get IP address to make pseudo header in transport layer?

We know that UDP checksum's pseudo header contains the most important parts of the IP header, that is, source and destination address, protocol number and data length. I hope that the concept of IP ...
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1answer
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SNMPv2 to v3 conversion

Can I use a Cisco router to convert SNMPv2 from an end device in one network to SNMPv3 and the C&M software in another network? The end device can only handle SNMPv2, but the C&M community is ...
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2answers
104 views

Is it possible for TCP can accept out of order segments?

TCP is connection-oriented protocol whereas IP isn't connection-oriented protocol. Any packets before sending into transport layer sorted operation must have been done in network layer. That's why we ...
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2answers
35 views

Do routers overwrite options of IP packets?

If i use IP options to send secret messages outside of the network using for example EIP, will the router replace them before sending out to the internet?
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2answers
199 views

Why can IPv4 and IPv6 use strict source routing(in options field) and flow label respectively inspite of connectionless protocol?

In IPv4 option field one field option is source routing option this means packet will always be routed by router Or not. Packet can also be routed by source such routing is known as source routing. ...
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1answer
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Does IPv4 of all devices follow this standard xxx.xxx.x.x?

I think the title says it all. I haven't found the answer anywhere else on the internet.
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Ping a host on the same network with special IP 0.0.0.0/8

I am trying to ping the host 192.168.1.5 from my computer. This works good. The subnet mask of the IP is 255.255.255.0, so the private IP 0.0.0.5 can also be used to ping the same host. But that ...
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140 views

Class D network for multicasting between group

We know Multicasting is defined as a single source sending to multiple recipients on a network when the receiver broadcasts a signal for acceptance. Multicasting has its own Class D IP addressing ...
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Can I assign one of my publicly available IP address to my AWS instance?

I would like to be able to use one of my publicly accessible ip addresses directly with my aws cloud instance. Is there a way I can assign or transfer one of my ip address to aws? My ARIN registry ...
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Do any subnets "Network ID" AKA "Network Address" always have an even number as the last octet? [duplicate]

Should a subnet have a "Network ID" AKA "Network Address" (eg: the first address, which is always unusable, and is the boundary between the previous subnet and the current subnet) ...
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1answer
42 views

Are routers doing NATP possibly run out of ports?

NATP helps each connection on the client device gain a "temporary identity" on the internet, by maintaining a one-to-one relationship between its local ip-port to a WAN ip-port. The binding ...
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1answer
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how does a host learn about other hosts IP addresses connected on the same subnet? [duplicate]

My question is similar to one posted [here][1] But answers are not understandable to me. How can a host (say my laptop) learn about IP addresses of other devices (say my phone) on the same subnet. ...
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3answers
349 views

Questions about NAT

So i just started learning about NAT and networking in general. As powerful as this technology may seem, it was specifically made for reducing the amount of IPV4 addresses used throughout the internet,...
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1answer
114 views

What are the negative impacts of using non RFC1918 addresses on a private network?

I work for a company overseeing network design of a large industrial system. For our purposes, it's a backbone network that other stakeholders have their own L3VPNs defined on. It is a network with ...
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1answer
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Assigning static IP address from the DHCP pool range on Cisco 800 series

What happens if I assign a static IP address to a device in a LAN where there is an active DHCP server and the address falls within the configured DHCP pool and DHCP server is Cisco 800 Series? Most ...
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1answer
64 views

I cant ping across Lan?

Current configuration : 2695 bytes ! version 15.1 no service timestamps log datetime msec no service timestamps debug datetime msec service password-encryption ! hostname ...
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2answers
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How does RIRs actually ensure IP ranges ownership

I'm currently learning about CIDR, subnets and IPv4 classes. I understood that IPv4 classes were used to route traffic in the beginning but nowadays we use "dynamic" subnet masks with the ...
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1answer
72 views

How does a device receive default gateway IP address?

When and how does a device get information about default gateway in LAN? I know you can define default gateway statically, but which protocol is used when it is not statically defined? Is it from ...
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Divide IPv4 network into subnets in a SPECIFIC order [duplicate]

My private addresses start at 10.10.0.0/16. I must make 2 subnets with 120 and 450 starting with the 120 one and not leaving any unnecessarily unused addresses. Let me remark, it's IMPERATIVE that the ...
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2answers
60 views

Are the IPv4 datagram addresses the corresponding public addresses, or the private addresses?

Inside the IPv4 datagram, there are the source and destination IP addresses. The first indicates the IPv4 of the source host, and the second indicates the IPv4 of the destination host. Are these ...
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2answers
119 views

Why do we need private IP address range?

When it comes to local networks, you have the freedom to use any IP address you want for your network since it doesn't need to communicate on the internet with other devices. However, the RFC ...
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A question from an online subnetting quiz [duplicate]

Does anyone know the last usable host IP address for the 172.45.120.0/23 network? And an explanation of how you got the answer? It's a multiple choice question on an online subnetting quiz. I'm ...
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1answer
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Why is my assignment asking me use 172.16.0.0 private addressing and IPv4 sub netted Class C address Scheme?

I am doing a project for Cybersecurity and trying to build a college campus network. The complete instructions read: LAN infrastructure layouts for all campuses. • Represent multiple building/...
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3k views

Why does one say IP fragmentation is bad and to be avoided when in reality data always needs to be fragmented for MTU compatibility?

Why does one say fragmentation is bad and must be avoided due to performance issues when in reality fragmentation intrinsically occurs within the communication ? Example: User1 wants to send 100 000 ...
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1answer
44 views

How routers route packets to a specific network

As I understand it, routers route packets to a specific network based on network id and of course the network id must be unique on the Internet, now the question is: maybe there are billions of ...
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2answers
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rules regarding IPV4 fragments and piecing them together

I'm rolling off my own TCP/IP stack for DOS and I have a question on IPV4 packets. Assuming that a client sends multiple IPV4 fragments, I would predict the MF flag would be set for every fragment ...
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1answer
53 views

How is the subnet mask detected over the internet with CIDR (classless inter domain routing)?

Lets say there are two public IP addresses. One is 21.120.12.8/16 and the other is 21.120.12.8/8, they are different network IDs but when used over the internet how are they both differentiated? Or is ...
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Extract Palo Alto ACC stats in text format

I have a Palo Alto p220 firewall, which acts as a virtual router at the same time. I would like to get the traffic data (download/upload in bytes per IP) in a format, which I could then parse on my ...
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1answer
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What is the maximum number of networks in IPv4?

From my understanding, in IPv4 addressing, the first 2 octets identify the network, meaning 2^16 networks can exist. But that doesn't seem even closly enough as the population in even USA is above 300 ...
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Basic conceptual questions about network interfaces

I have some basic questions as I am trying to understand the concept of network interfaces a bit better. Is network interface same as network interface card (NIC)? If not, what's the difference. What ...
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894 views

Can a client-side outbound TCP port be reused concurrently for multiple destinations?

Can a client-side outbound TCP port be reused concurrently for multiple destinations? If it's possible, this would let NAT gateways milk an IP Address much more, and make it practically impossible to ...
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32 views

ECT Marked ICMP Responses

For ongoing research I'm conducting, I'm measuring the modification of ECT fields of the IPv[46] header. To do this I'm relying on ICMP quotations to inspect what packets 'look like' as they traverse ...
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Into how many subnets can you split this address range up at most? [duplicate]

Let's say there is address range given: 124.33.66.0/23. Into how many subnets can this address range be splitted up at most if each of these subnets includes at least 5 devices? I don't know where to ...

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