Questions tagged [ipv4]

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

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Ping to default gateway failing

I am trying to ping to a default gateway which i have configured as 171.2.0.1 but somehow the ping is failing . I am new to network domain so i have less idea about it . Any help is appreciated .This ...
6 votes
2 answers
2k views

Why can I ping IP addresses from 127.0.0.1 to 127.255.255.254?

I thought that the loopback IP address of my machine is 127.0.0.1. I do not understand why am I able to ping IP addresses until 127.255.255.254.
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 ...
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-...
5 votes
1 answer
186 views

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 ...
3 votes
2 answers
2k views

What this subnetting restriction means

I was reading Data Communication book by Forouzan in which there is a one restriction put on CIDR subnetting by Internet authorities: First IP address in the block should be evenly divisible by the ...
1 vote
1 answer
247 views

"SWIP" Equivalent for RIPE?

With ARIN, I was familiar with using "SWIP" for IP blocks via an ORG and a POC. With RIPE, however, it seems that it's different. I have access to a RIPE account where I can make the changes,...
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
1 answer
225 views

How can I configure a Cisco router 4300 to allow internal server ip:80 to be accessed on public ip:4500

I have an internal web server on port 80. I need help commands maybe to configure port forwarding to access the server on my private network from a public IP Current running config interface ...
0 votes
2 answers
752 views

Can I run 2 separate ranges on the same physical network

My current set up is 1 router and 2 switches, the router being 192.168.10.1 with a connection to each switch then 8 and 10 devices on the 2 switches all 192.168.10.x I have an NVR with 2 ports, 1 of ...
0 votes
1 answer
42 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 ...
4 votes
4 answers
2k views

Is it possible to brute force search/guess symmetric NAT port prediction for hole punching?

Say we have two clients A and B that wish to connect to each other, both behind symmetric NAT's NA and NB respectively. Also there is a rendezvous server S that exists to assist clients A and B with ...
0 votes
2 answers
56 views

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 ...
5 votes
2 answers
1k 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 ...
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
3 answers
144 views

Meaningless bits in CIDR notation

Is specifying meaningless bits valid syntax in CIDR notation? For instance, the netmask of 192.168.13.0/16 is 255.255.0.0. In this case, the last two octets (00001101 00000000) are meaningless because ...
6 votes
1 answer
201 views

What's the domain of an IP?

CIDR stands for "Classless Inter-Domain Routing". But what's a domain in this case? Seems to not be the same kind of domain as DNS deals with...
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 ...
0 votes
0 answers
12 views

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 ...
24 votes
7 answers
9k views

Does CIDR really "do away" with IP address classes?

I am still struggling to understand to what extent CIDR really renders IP address classes obsolete. Here's what I understood so far: It's ridiculously inefficient (and impossible, too) to assign ...
1 vote
1 answer
67 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 ...
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 ...
0 votes
1 answer
42 views

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 ...
9 votes
4 answers
14k views

Network Byte Order

According to big endian byte ordering or network byte order the bits are transmitted in this order: bits 0-7 first, then bits 8-15, then 16-23 and bits 24-31 last. Does this means that bits from ...
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
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 ...
3 votes
1 answer
333 views

What is the maximum value that a receiver can set in its advertising window

I know an advertising window is set by the receiver to inform the sender not to send more than what is advertised in the receiver's window to avoid packet loss due to overflow of packets at receiver(...
0 votes
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. ...
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....
2 votes
1 answer
95 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 (...
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
0 answers
7 views

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
88 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 ...
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 ...
5 votes
4 answers
12k views

Network setup for multiple devices with the same IP

Because I do not find the correct question that I can ask google, due to the lack of terminology. I'm trying to ask it here. Please have patience. My Question is similar to the questions asked here ...
1 vote
1 answer
45 views

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 ...
0 votes
3 answers
75 views

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 ...
3 votes
2 answers
304 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. ...
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 ...
129 votes
6 answers
807k views

How do you calculate the prefix, network, subnet, and host numbers?

Example: IP: 128.42.5.4 In binary: 10000000 00101010 00000101 00000100 Subnet: 255.255.248.0 How could you determine the prefix, network, subnet, and host numbers?
0 votes
0 answers
11 views

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, ...
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 ...
52 votes
10 answers
95k views

Reason for both a MAC and an IP address

If my computer has an IP address,why does it need a MAC address?
7 votes
7 answers
3k views

Why is classful addressing considered waste?

I am trying to understand the addressing strategies. But there is something which I can't grasp. Maybe I am missing a very basic point, if so, I am sorry beforehand. From my researches, let's say, if ...

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