Questions tagged [ipv4]

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

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Are network IP addresses ever used as source or destination IPs? [duplicate]

The first IP address of an IP subnet is the network address, which stands for the whole network, while the last address is the broadcast address. As far as I understand, we never really send packets ...
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15 views

TCP connection closes instantly (without timeout) when I change my IP address through the windows network and sharing center [closed]

I have tcp connection to some tcp server on internet. Tcp client is a simple application that I have created which works on my computer. The problem is that when I change my ip address through the ...
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IPv4 header length maximum size [closed]

The minimum header length is 20 bytes but in the datagram the IHL is only assigned 4 bits. Why it is like that?
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34 views

IPv4 maximum datagram size

The IPv4 datagram consists of two parts:the header length and the payload. The maximum header size is 60 bytes and minimum is 20 bytes. The maximum size of the data can be 65515 bytes. So why the ...
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Why does `curl <this machine's IP>` behave differently than `curl localhost`? [closed]

I have two Raspberry Pis on my network - let's call them Pi and Rho. I'm trying to set up port forwarding via ssh tunnel between them, such that an application can connect to a port on Rho and get ...
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Cannot port forward traffic from public IP (WAN) to OpenVPN (remote) clients [closed]

I'm looking for some advice here or a nudge in the right direction, seeing as I've reached an apparent dead end. I have a static IP for my business (200.78.xxx.xxx) and I set up an OpenVPN Server on ...
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1answer
127 views

Broadcasting to unknown Class C Network

I am trying to use python to broadcast to my local network, and I cannot find a way to get the subnet mask. I have been suggested to use the default Class C network subnet mask 255.255.255.0, and use ...
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2answers
43 views

Where are broadcast packages filtered out

When I have one network with a switch. Within that network I have 10 PC. Halve of them are configured within the 192.168.1.0/24 range and the other halve is configured at 192.168.2.0/24. This means I ...
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1answer
36 views

Find Routes not containing these subnets [closed]

Let's say I have 1000 ranges and I would like to make routes that doesn't match these ranges, anyone has any particular tips or tools to share beside doing math ? Example : I have these ranges 13....
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1answer
53 views

Why Classful addressing is not in use if we can subnet them?

So, Let's think that organization needs 5000 IP addresses. Giving 20 C Class IP addresses will cause of adding 20 entries for ISP router. That's problem. We could give Class B IP address, but that ...
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19 views

How to find minimum of hosts bits needed and assign equally to five subnets? [duplicate]

I have a 192.168.1.0/18 network block. How do I determine the minimum number of host bits to be borrowed and assigned equally to five subnets? How to calculate the number of users that can be ...
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2answers
49 views

The MSB of IPv4 flags

In IPv4 header, there is 3 bits field called "flags". The MSB of this field must be reset to zero (as many networking blogs say without telling why). i want to know what will happen if I managed to ...
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2answers
57 views

Do NAT devices need to have private IP addresses?

If a NAT's job is to create mappings between internal ip/port pairs and external ip/port pairs with one Internet-routable IP address, does a NAT need a private IP address for itself? I think one ...
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2answers
55 views

Routing Table Settings To Access An Internal Network Through VPN

I have a remote computer behind a VPN (which I have no control of). The IT team of the remote factory wanted me to install Palo Alto Networks' Global Protect program to access the VPN, which is ...
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1answer
69 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 ...
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58 views

When a packet is received, how does it know which internal machine to send it to?

I am familiar with ARP and routing, but I think I am failing to put two and two together here. On an IPv4 packet we have the source IP address, which allows any router to send the response back to the ...
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1answer
37 views

Is an IP broadcast always a layer 2 broadcast also

On my PC I see 255.255.255.255 in ARP with MAC FF:FF:FF:FF:FF:FF, so I'm assuming that in most cases the L3 broadcast is also encapsulated into an L2 broadcast frame, but is this standardized? For a ...
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2answers
52 views

Why can some people use public ip address to access a server from an internal network with the client device within the internal network

As the title suggests. I find it mind breaking to think how network architecture can differ to allow/not allow using public IP address to access a server within internal network from within the ...
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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 ...
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2answers
324 views

MTU the most Confusing Networking term. Lot of questions

I have ton of questions and i feel this is most confusing term for me. The more i read the confusion deepens. I am not able to connect dots. please help. Do we need MTU adjustment with EoMPLS/dot1q ...
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1answer
38 views

IPv4 Subnetting for 1200 or more devices for WiFi

I am currently looking over my schools existing Subnets and their usage. Some seem to be sufficent, others not so much. What is the best practice when you need to support 1200 or more devices on a ...
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2answers
65 views

Question about the destination IP inside an IPv4 packet

I'm reading about link and network layers for the first time and I'm trying to put the pieces together to understand how they work together. My question may not have to do with the link layer but I'm ...
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Given a subnet mask, how can I determine which addresses can be assigned to public network hosts? [duplicate]

For example, I'm given a subnet mask of 255.255.255.248 and need to determine from a list - 16.70.118.63 134.178.18.56 200.47.224.159 68.111.178.93 192.168.16.87 217.37.10.192 - which addresses can be ...
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Building simple network configuration [duplicate]

For the below network configuration I need to propose an IP addresses, netmask and anything else obvious that I am possibly forgetting. The network is built of four Computers, Router and a Switch. I ...
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5answers
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Usage of 192.168.xxx, 172.xxx and 10.xxx in private networks

I know that the organization that distributes IP addresses decided to assign 192.168.xxx, 172.xxx and 10.xxx to private networks. However, I thought that private networks have their own address space ...
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23 views

Is it possible to access 127.0.0.xxx in anyway [closed]

So I've been configuring my network at work. We've got a lot of devices from NAS servers to Dante AoIP devices. While configuring some of my devices I managed to set the IP adress of one device to ...
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3answers
2k views

Does NAT violate end to end argument?

Does NAT violate end to end argument? What does end to end argument means in this context?
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How is it possible to have a default gateway outside of the network range of any interface? [closed]

I always thought that the default gateways has to be on the same network as the server/client trying to connect to the internet. However today I rented a server from Hetzner and the server is able to ...
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2answers
42 views

How TCP connections between origin and node servers over a BGP Anycast gets established?

Server A and B have the same IP address with anycast. Server B connects to the origin server that is very close to server A and very far away from server B, since server A is closer, the response will ...
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1answer
46 views

Remotely Connecting an IPv6 Computer to a IPv6 Private Web Server

I have a private web server at my office, and I want to access that server remotely at my house via IPv6. My office has both IPv4 and IPv6 enabled, but my home has only IPv6. IPv4 works, but I have ...
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2answers
81 views

Loopback with / 32

When we dealing with bgp, osp. Why do we especially use loopback interfaces with / 32!? Is there an advantage or something different from other subnets like 24.
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Why is the source / destination address ordering in IPv4 and IPv6 headers opposite of Ethernet source and destination MAC addresses? [duplicate]

Engineers always do things for a reason. I've noticed that in Ethernet frames, the ordering is destination MAC address first, and then the source MAC address. What's the reason for reversing the ...
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1answer
43 views

Setting the network address freely [duplicate]

I'm trying to understand IP Addressing, but there's something what's still not clear for me. With mask 1111111.1111111.1111111.00000000 (/24) Am I able to set network address "freely" like this? ...
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1answer
40 views

Next Header field in IPv6 vs Protocol field in IPv4, any difference?

So I am new to the IPv6 concept, and I seen that the Protocol field seems to be replaced with Next Header, and I have a question. Question: Is Next Header a complete replace of Protocol, or is they ...
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3answers
118 views

What is the intuition behind subnetting a base IP?

Take a look at this picture: My professor usually gives a topology like this and gives me a base IP. Let's say the base IP given is: 223.1.0.0/24. We're then asked to construct the given topology by ...
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1answer
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Confusion about IANA “Protocol Numbers” registery

In the IANA registery for "Protocol Numbers", there listed 2 IP protocol versions: IPv4 at #4 and IPv6 at #41. Their "protocol" column says IPv[46] Encapsulation, and "reference" column points to 2 ...
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3answers
171 views

Will pinging the multicast “all hosts” IP 224.0.0.1 fill my ARP cache with all hosts on my current subnet?

Just wondering in case I ever have a want / need to see all the hosts on my subnet.
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1answer
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Typical signs of fragmented IP fragments

Given, for example, a Wireshark trace, how can I identify that the IP fragments that I am sending are themselves being fragmented? For example, if I'm sending 1500 byte IP fragments, and the server ...
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1answer
133 views

How does NAT ensure that every machine has a unique public IP?

I am trying to understand the distinction between public and private IP addresses in IPv4 networking. The picture I've been told has some problems with it, so I would like to present it here and ask ...
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4answers
5k views

Why is 10.1.255.255 an invalid broadcast address?

I’ve been following the CCENT official certification book(100-105) and came upon this question in the “do I know this already?” quiz. The books only covered /24 subnetting only so far. Which of the ...
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1answer
117 views

Can communication to broadcast 224.0.0.1 be made to reach hosts outside of the local subnet?

I been asked the question if it is possible for an a IP host to use multicast to address 224.0.0.1 in order to reach (and get a response from) another host which is not on the local network segment ...
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1answer
49 views

When IP header of length 22bytes is there then how padding will work?

My base IPv4 header of 20bytes + 2bytes i used for Options making it 22bytes means 176bits so padding will add 16 Zeroes to make it multiple of 32? is this correct way to understand? Boundary of ...
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1answer
67 views

Which IPv4 options must be copied on fragmentation and why?

In RFC 791 page 14 it says The copied flag indicates that this option is copied into all fragments on fragmentation. 0 = not copied 1 = copied If I understand correctly it is possible ...
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2answers
401 views

What's the DF flag mean in IP packet header?

In the IP package, there is DF flag: Don't Fragment. I have doubt about it, is it mean let all the L3 device do not to fragment the IP packet (if the L3 device found it is bigger than MTU, device ...
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2answers
21 views

Can 2 Directly connected PCs having the same network ID but different subnet mask talk? [duplicate]

If Pc1 has IP 192.168.10.2 / 24 ---> Network ID : 192.168.10.0 and Pc2 has IP 192.168.11.3 / 23 ---> Network ID : 192.168.10.0 directly connected (no switches no routers). Why cant i ping? But if ...
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1answer
60 views

Floating Number representation for Ipv4 address

I'm wondering if we can have floating point(3.3 9.9 2.2 6.3) or Hexadecimal(6A.65.D5.77) representation for Ipv4 address that is also 32 bit long to compensate for IPv4 address shortage. Same ...
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1answer
485 views

Why the IPv4 need Don't fragment Flag?

Why the IPv4 need Don't fragment Flag? We know the IPv4 Flags options are: Reserved bit, Don't fragment, More fragments, fragment offset options. Why there need the Don't fragment Flag? if it is ...
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1answer
69 views

How to understand the Flags is IP_MF, what will happen?

For data packets whose length exceeds the MTU of the interface, fragmentation processing is required. The fields related to fragmentation in the IP header are as follows: Identification - Used to ...
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4answers
167 views

How do devices connected to a switch get their IPs?

It should go without saying, I'm new and still learning about networking. One of the things I'm not clear on and couldn't find a satisfying answer to, although I've done some digging around, is how ...
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2answers
200 views

Global BGP Routing only by only importing supernet prefixes

I was wondering if global IPv4 Routing can be technically achieved only by importing from the ISP Provider (providing us with a IPv4 BGP full table) a subset from the BGPv4 routes (i.e. all prefixes ...

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