Questions tagged [ipv4]

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

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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
55 views

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
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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
15 views

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
45 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
120 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
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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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0 votes
3 answers
69 views

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
100 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
104 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
17 views

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
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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
96 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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0 votes
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
49 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
123 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
17 views

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://) ...
0 votes
1 answer
22 views

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 ...
0 votes
2 answers
75 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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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 ...
0 votes
0 answers
10 views

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
71 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
29 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
138 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
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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
79 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
130 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
61 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
331 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 (...
1 vote
2 answers
772 views

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 ...
's user avatar
2 votes
1 answer
1k views

Which one is 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 ...
0 votes
2 answers
71 views

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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1 answer
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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 ...
1 vote
1 answer
112 views

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 ...
0 votes
1 answer
281 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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-1 votes
1 answer
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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 ...
0 votes
1 answer
371 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 ...
0 votes
1 answer
275 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 ...
0 votes
1 answer
112 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 ...
0 votes
1 answer
112 views

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 ...
0 votes
2 answers
360 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 ...
1 vote
2 answers
46 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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