Questions tagged [ipv4]

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

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Valid uses for IPv4 Options [Community-Wiki]

Engineers building firewall rules often block all IPv4 packets with IPv4 Options set in the header. However, there are a few common and valid use-cases for IPv4 Options. This Q&A is intended to ...
0 votes
2 answers
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Public IP Configuration which has a private gateway

I bought a public IP from my ISP and they provided me with the following details. WAN IP :10.129.69.157 LAN IP : 196.188.173.32/30 How do I configure this on my side ? The told me to do configure as ...
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3 answers
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Is `0.0.0.0/1` a valid IP address? If so, what does it indicate?

I know that 0.0.0.0/0 represents a default route. But I would like to understand what does 0.0.0.0/1 represents? Is it even a valid thing in networking?
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1 answer
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Can't find a device on my network

I have a device on my network that is at a static address (192.168.3.1). This device is connected to a network switch, that is also connected to the rest of my network. My problem is that I need to be ...
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0 answers
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What's the big deal with "192.168" in ipv4 networking addresses? [duplicate]

What's the big deal with 192.168 in ipv4? Why can't it be like: 111.473.6946? Please explain, networking experts.
-1 votes
0 answers
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Is this a valid subnet to implement [duplicate]

I'm trying to consolidate my understanding of networks, particularly routing and IP addressing. I understand that, for instance, IP address 192.168.1.0 with a subnet mask of /28 (i.e. last 4 bits ...
0 votes
2 answers
38 views

Cannot ping/access single host over VPN [closed]

I am running openVPN server on pfSense machine, which is also the router of the network. This network has several VLAN's, where only single one of them is of interest - 10.0.100.0/22. The openVPN ...
0 votes
1 answer
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How to correctly setup a DHCP server in the following network?

So, I've got the following Network Configuration: Assume that, on the graph, "PCs" can be any device that needs an IP(apart from a router). Now, as explained on my title, I want to run a ...
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1 answer
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How to connect GNS3 to loopback adapter on Windows 10

I'm trying to have a simple topology by connecting a router (c7200) and the local machine which is windows 10. For this I use GNS3 GUI (not the VM application). I have to do that, due to the limit of ...
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0 answers
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What am I missing, Super netting/sub netting, Communication problem [duplicate]

enter image description here CompTIA+ use this as an illustration to explain superneting, I have been trying to recreate this to help follow the understanding, so far I have managed to create this ...
0 votes
1 answer
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Packet tracer overlapping error [duplicate]

I'm very new to packet tracer (day 3) I seem to get an overlapping error message, on 0/0/0 - 192.168.0.2/24, I couldn't assign 0.3 to interface 0/0/1 (overlapping) so I assigned 0.3 to PC0 and tried 0....
0 votes
3 answers
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Lost the Static IP/network settings of a device

We have a physical device (lab instrument) that we can only connect to via ethernet. Unfortunately a static IP was set with network settings and these settings has been lost. We connected our computer ...
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3 answers
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Access to systems with the same IP address but various port number in another network?

I have some knowledge of networking but not much, so I appreciate knowing from the experts. modified part I have 10 devices(PLCs) with the same IP address "192.168.42.2" that I want to ...
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5 votes
1 answer
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Does the IP header have a "Padding" field?

I found two images of the IP header, one image shows a field called "Padding", while the other image don't show the "Padding" field: Which one of these two images is correct?
1 vote
1 answer
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What is the Logic of AND and OR operations in subnetting?

To calculate subnetting for given IP address and the subnet address, we do AND operation first to get the network address and the first usable IP address of the subnet. Why do we use AND? I know it ...
0 votes
1 answer
44 views

Is it possible to send network messages with "Fake" Local Network(192.168.x.x) destination IP but actually reaches the destination via internet?

I am configuring a MySQL server that is only intended for computers from internal network/local network machines to access. Now MySQL has a "bind IP address" setting that, if I set it to the ...
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2 answers
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In what context is this IP address / subnet mask valid?

Is this IP address ever valid? I am reviewing a CCNA course taken by thousands of previous students. The information I have isn't in the right order / context, but I noticed that this IP address was ...
0 votes
0 answers
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How are we still able to use IPv4 address even with NAT? [duplicate]

My question is why haven't we run out of IPv4 public IP as well because now almost all home has a router which is assigned a public IP. Is it possible to have multiple layers of NAT on the router-ISP ...
0 votes
1 answer
77 views

How to stop broadcasting WAN network group to LAN network group?

First, I'm not really good at networking terminologies, So I'll explain the case as simple as possible. I have a PFSense set up, my PFsense gets its internet through its WAN IP 192.168.10.2 and ...
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0 answers
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What would be the correct way to go about subnetting an IP address for two networks? [duplicate]

I am struggling with how to proceed with this. I have started by converting the IP address into binary. If somebody could just give me a push in the right direction I would appreciate it! There are ...
1 vote
2 answers
233 views

What should we do if the number of bytes to be transferred are not in multiples of eight in ipv4? [duplicate]

(it is take from book called special edition tcp ip, pic taken for better formatting and ease to read) Theory that I am trying to understand-: So i found a question that is relevant to this-: ->a ...
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1 vote
1 answer
154 views

How is 65535 bytes is total length of IP datagram?

The maximum size of an IPv4 packet is 65,535 because the Total Length field is a 16-bit unsigned integer, which has a possible 65,536 values (from 0 to 65,535). This created 2 confusions for me. Say ...
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3 answers
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How to use IP pool

I am just beginner, I just want to setup my mini data center and for testing i get a FTTH connection and /30 ip pool, ISP reply is something like that, "IP Pool 103.15.xx.xx/30 has been assigned ...
1 vote
2 answers
104 views

Why shortened version of IP4 exists and it is undocumented but supported everywhere?

For example there is an IP address 192.168.0.1 It is clear that you can use it as the full line, but try that one 192.168.1 It will also work, and it will be automatically converted to 192.168.0.1 ...
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1 answer
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DHCP Discover Broadcast and its IP (255.255.255) [duplicate]

Cheers, I am trying to learn more about DHCP, and when studying about the session that DHCP goes through every one mentions that it broadcasts a discover message at IP: (255.255.255.255) (as seen here ...
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1 answer
163 views

VLAN routing on the same subnet

Consider following situation: You have 10.3.0.0/16 network without any VLANs. Now You want to divide it... You want Your IT department be able to reach the entire network, but sales department only ...
0 votes
0 answers
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Why does a router need 2 IP address? [duplicate]

Suppose there are 2 PC and 1 router in "LAN1", now if PC1 wants to communicate with PC2, it will need to uniquely identify PC2. So, PC2 gets a private IP that no other PC in LAN1 will have. ...
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0 answers
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Dividing network into subnets [duplicate]

My teacher uploaded this example question and solution as explanation of the topic: I watched some videos about it but none of them made it fully clear, what I don't understand here is: What are ...
4 votes
1 answer
100 views

How Can a VPC ping the Router through an Etherswitch that behaves in one port as router and in the other as switch

In the following topology my main purpose is to: 1)PC11 ping Router(R) 2)PC11 ping PC13 ESW10: In gig0/3 has the no switchport command and a given IP address. In gig0/2 it has the switchport access ...
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1 vote
1 answer
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How does providing IPv4 occur through mobile internet?

I've read that there are 2 types of IPv4 addresses: public ip-address and private ip-address. Public ip is used to connect devices to the internet (WAN). There's always an example about routers that ...
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2 votes
1 answer
123 views

Custom option in IP header

I would like to add (or piggyback on an existing not used) a custom option to the IP header. I've full control of the IP stack at both end points, but I've no control on all the hops in the route (...
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3 answers
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why ip adresses are divided into network portion and host portion when we already have NAT [duplicate]

I don't understand why ip adresses are divided into network portion and host portion? is the host portion really necessary when we already have NAT? for example, if ip addresses only have network ...
2 votes
1 answer
56 views

Fragments taking different routes?

I have trouble understanding why sometimes it occurs that during IP fragmentation certain fragments take different routes. I was following this the second example: https://www.gatevidyalay.com/ip-...
1 vote
1 answer
195 views

Understand DSCP and Precedence Values in Ipv4 or Ipv6 packet

I read from this website to understand DSCP and it's corresponding IP precedence value. For example DSCP value is '000 000' which Drop Probability is N/A(never happen) and it's Equivalent IP ...
0 votes
1 answer
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Does socket address include transport protocol (http://)? [closed]

Let's say I have the following: http://ip_addr:port This is supposedly called the socket address (see sources below), but I can't find a conclusive answer anywhere if the transport protocol (http://) ...
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1 answer
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Enquiries regarding securing strong password and ssh

I am a beginner in computer network and I have done some research with regards on how to do IP configuration on PC and routers. However, I am not sure on how to configure strong password and ssh based ...
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2 answers
77 views

Why would we want to subnet/change CIDR of private addresses?

I am studying for my CCNA and my current topic is subnetting. I understand how subnetting works and how to subnet (calculate the network IP, the amount of hosts, broadcast, etc). However, I can't seem ...
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0 answers
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Subnetting and dividing networks [duplicate]

I am currently learning about how subnetting works and I need to get rid of some confusion. If we divide networks like this, and assign each network a different IP address (192.168.1.0, 192.168.2.0, ...
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9 votes
6 answers
2k views

Is CIDR IP format currently in use?

I'm reading a book that says that, historically, there have been three ways to interpret IP addresses: Classful Subnetting with subnet masks Classless Inter-Domain Routing(CIDR), supernetting. My ...
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0 answers
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What is the routing prefix (in format: address of a network/bit-length of the prefix) for the smallest subnet that contains these four hosts? [duplicate]

A computer network has hosts with the following IP addresses: 124.127.64.147 124.127.64.151 124.127.64.155 124.127.64.156 What is the routing prefix (in format: address of a network/bit-length of the ...
2 votes
1 answer
76 views

Which ranges of IPv6 and IPv4 do requests to the local network and the host?

I'm looking for the range of IP address that is bound to the local network or the host itself. So far for IPv4 I found: 10.0.0.0 - 10.255.255.255 172.16.0.0 - 172.31.255.255 192.168.0.0 - 192.168.255....
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0 answers
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Subnetting an network into different number of subnets [duplicate]

Assuming you are using a Class C IP address (195.16.1.0) and you need to create the following numbers of subnets for your network plan. For each of the numbers of required subnets below, provide how ...
1 vote
1 answer
34 views

Does a Transparent Firewall need a Default gateway if directly connected to a layer 3 device that is actively performing routing?

Good folks of the Network Engineering stack! I have a question that I assume most people could answer in their sleep. To better illustrate my question, I've provided a sketch of my network below. In ...
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1 vote
1 answer
225 views

Can I set fragmented IPv4 packet's DF bit to '1'? [duplicate]

If make DF to 1, can I confirm that fragmented packet with DF=1 will go through routers to the dest IP without any reassembly and re-fragmentation?
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2 answers
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Could we use private IP address as directed broadcast address?

We know that private IP addresses ranges of class A, class B, class C are 10.0.0.0-10.0.0.255, 172.16.0.0-172.16.255.255, 192.168.0.0-192.168.255.255 respectively. My first questions is that first and ...
-1 votes
1 answer
44 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 ...
1 vote
2 answers
101 views

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 ...
0 votes
1 answer
168 views

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 ...
0 votes
1 answer
64 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 ...
1 vote
5 answers
413 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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