Questions tagged [ipv4]

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

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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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Packet tracer - why “show ip route” shows network address

This is just a quick question I am wondering out of curiosity. When I set up a network in packet tracer, why does "show IP route" show the network address (example: 199.120.5.64/27) and not the IP ...
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Sending an ipv4 packet to the Destination IP without a router?

We are replacing a "RF modem + Router system" with a Software Defined Receiver. After analyzing the receiving and sent signals we found out that an IPv4 UDP packets have been sent and received. 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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Loopback interfaces subnets [closed]

Assuming that loopback interface is always alone in its network, what are the practical reasons to have IPv4 subnet prefix shorter than /32 for these interfaces? Moreover, why according to various ...
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How can I assign a static public ip to a machine behind a router?

I know about port-forwarding, but I'm interested in how to make a machine on a local network available to the public internet without port-forwarding.
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Is the routing table used when sending IP packets to a host on the same LAN in ipv4?

I am having trouble understanding the steps in order to send an ip packet to another host on the same LAN. Most sources online that I have read and people I have talked to say that the host uses the ...
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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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Routing with private addresses

Let's say that we have a private network, with private addresses and a NAT enabled router at the end. If the router is misconfigured and routes traffic to the global internet, keeping as source ...
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Combining NAT an tunneling

I was reading a text and a doubt came to mind. Suppose there is an interface in a router that implements NAT. That same interface is the extreme of a tunnel. If I was to send a message through said ...
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Is a TCP server limited to 65535 clients?

There are 65535 TCP port numbers, does that mean only 65535 clients can connect to a TCP server? One might think that this places a hard limit on the number of clients that a single computer/...
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One client: static IP vs Static lease DHCP vs. DHCP limited range to 1 slot

I want to attach one client (only 1 maximum) to network router ethernet port. I want to always know the client's IP address, for my port forwarding settings. Using DHCP with range the client IP could ...
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“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,...
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Please solve this question [duplicate]

b) An organization is granted the block 211.17.180.0/24. The administrator wants to create 32 subnets. i. Find the subnet mask. ii. Find the number of addresses in each subnet. iii. Find the first ...
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By General Convention if we say the Frame size is 1KB do we take it as a 2^10 Bytes or 10^3 Bytes

In my academic we generally follow 2^10 Byte approach , I m really at loss is it by convention only at my college or something which is accepted widely
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Can you keep DHCP addresses from your ISP

I have my modem configured for bridge mode. I get one IPv4 for my router and one goes to my server for public access. If I static assigned these IPv4 address would I keep them as long as no one else ...
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385 views

Is not 192.168.88.1 (192.168.*.*) always an “internal” IP address?

I had some headache with a proxy setup which I couldn't figure out. Turns out that only "127.0.0.1" and "localhost" were recognized as "localhost" or "internal" ...
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How to find the first and last address in the FIRST AND LAST SUBNET [duplicate]

So there's a problem that literally stress me out every time I look at it. It's like I almost understand it until I get to knowing how to find the first and last host in the LAST address (last subnet)....
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Are there broadcast/collision domains on non-Ethernet networks?

What if we have routers or hosts connected via ATM, Frame Relay, or SONET; that is, what if we have IP over SONET, IP over ATM, IP over Frame Relay, etc., do we still have broadcast domains and ...
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1answer
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IPv4 and UDP/TCP packets inside of ICMP packet?

A week ago, after opening wireshark, i was surprised by seing a storm of ICMP packets from different IP addresses. While deep analysing of thoses packets, i noticed that those ICMP packets contains ...
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IPv4 and IPv6 Source Address field

Both the IPv4 and IPv6 headers contain the source address field. What are the reasons for including this field? Is it for to trace which who sent this packet if it get's lost?
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Are there public servers with a 192.168.X.X IP address?

I was wondering about the IPv4 problem and thought about one of the solutions where endpoints do not have their own public ip address, but rather an address only used within the VPN and a mapping by ...
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How does the IPv4 Total Header Length field & Fragmentation work together? [duplicate]

I recently learnt that the maximum value of the IPv4 Total Header Length field is 65,535 which equals approx. 65.5KB. To my understanding, it is different from the IHL field as it includes the ...
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Why does sub-netting not give us more addresses? [duplicate]

Sorry if this is dumb, but I am very knew to learning about networks. Here is my reasoning? Let's take the address, 24.50.12.4 if we subnet it with /16 then the network address is 24.50 + host is 0.0....
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How to find Best Fit Mask [duplicate]

How does i find the best fit netmask (i.e., resulting in as few host addresses as possible) for a network with 62 hosts in it? I don't have any class like A,B,C How can i find best fit netmask for ...
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Confusion about TTL when pinging

TTL value of a packet is supposed to decrease 1 at each router from 255 down to zero as follows: But when I ping to 8.8.8.8 the TTL starts at 253 and doesn't change: How can this be explained? Why ...
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Is 12.23.34.45/24 a valid IPv4 subnet definition? [duplicate]

I believe the question says it all: when referring to an IPv4 subnet, is it valid to use 12.23.34.45/24? If it is, is it equivalent to 12.23.34.0/24? If it is not, can you refer me to helpful ...
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Understanding IPV4 address range [duplicate]

I do have basic understanding of IP Address which is unique address for each System either in an organization or over the internet. But i want to understand what is IP address range Lets Say we have ...
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How does the shortage of IPv4 public IPs influence existing firewalls?

I came to know recently IPv4 public IP address pools are going to be exhausted soon. If IPv6 addresses are fully in use, all device vendors like Cisco, Fortinet, Palo Alto have to redesign their ...
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Why are IPv4 addresses running out?

I understand that we are running out (or ran out already?) of IPv4 addresses, but I don't really understand why that is. Right now, every home has its own IPv4 address (dynamically assigned, but still,...
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How does IP fragments assembled when identification number field is too small?

Please take reference from this question. It is said in RFC 6864 that if IP V4 IDs remain unique during MDL, it would limit speed to max 6.4Mbps. Now high speed devices generate data at a much higher ...
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Connecting to device which requires specific IP [closed]

[Disclaimer: I'm a complete networking novice, and this question might not even be well suited for this site. I welcome pointers to other stack exchanges if appropriate.] I'm trying to connect a ...
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What are some techniques to infer the subnet being used? [closed]

Given a list of thousands of IPv4 addresses and that you have no direct access to these hosts, is there a service or a methodology to infer a subnet that's possibly being used?
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What is the purpose of network address?

What is the purpose of network address? (aka subnet address, starting address of each subnet) For example in this network: 192.168.1.0/24 Why we should leave 192.168.1.0 address free?
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What is the point of ARP?

I'm a complete beginner at networking, but if I've understood this correctly, the gist of ARP is: We want to use high level adresses to the highest degree possible but ultimately, we actually need ...
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Private Public and Special IP addressing

Is the IP address 224.0.0.0 routable over the internet?
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Why are number of hosts on a subnet less than the number of combinations we can make with the bits remaining?

Suppose we have a Class C Subnet (255.255.255.0), why do we get to have 254 hosts on it even though we have 256 unique internal IPv4 addresses from 192.168.1.0 to 192.168.1.255? Even if we scale up ...
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Broadcasting traffic by 255.255.255.255 or by “subnet dot all ones”?

If a device wants to broadcast traffic does it send it to the "all ones" IP? (Which is 255.255.255.255)? Or does it send it to "the all ones of the subnet"? (For example if the subnet is 123.123.0.0/...
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Setting subnet mask to 255.255.255.255

If I want just 1 device to be on the network, can I set the subnet mask to 255.255.255.255? For example, the consider the network card configuration IP 10.0.0.10 mask 255.255.255.255 ...
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Understanding L2 Switch (Network Noob)

I currently have the setup on the left and it works just fine... I use it to transfer data between laptop and embedded systems hardware device. (Data...Not internet) Question: What would the set up on ...
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1answer
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TCP protocol mystery [closed]

I am attempting to compile, with pcap-filter, the following string: host yb-in-f91.1e100.n Obtained from the following command: netstat -t output line: tcp 0 0 os-info:portnum yb-in-f91.1e100.n ...
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Using IP addresses from IP pool given by ISP

My ISP says that it can provide an optic fiber connection with a pool of 4 static IP addresses (subnet 255.255.255.248 i think). My question is that if I get that connection, 1 ip will be used for ...
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Is the outgoing interface of a router in the same Subnet as the Incoming interface of the NEXT HOP router?

In the TCP/IP Volume 1, it is stated that ARP works only on the same subnet. Does this mean that the outgoing interface of a router is necessarily on the same subnet as the incoming interface of the ...
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What is the need for the NEXT HOP coloumn in the routing table when we already mention the OUTGOING INTERFACE in another coloumn?

If the OUTGOING INTERFACE is already mentioned in the routing table, it is natural that the next hop will necessarily be the router attached to the outgoing interface. Then why is there a separate ...
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different network mask and subnet mask and netmask [duplicate]

1- what is network mask? 2- what is subnet mask? is there any differnt between network mask and subnet mask? i'm tried to search about network mask and nothing found is it called netmask ? thank you
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Private IP Address Subnetting Standards. How strict are they today?

How strict is this standard today. The 172.16.0.0/12 range is: 172.16.0.0 – 172.31.255.255 Conceptual Config 172.Location.VLAN.Host Location A (10): VLAN 10 - 172.10.10.0/24 VLAN 20 - 172.10.20.0/...
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Same IP addresses with different CIDR notations, is it possible?

Can we have exactly same IP addresses with different CIDR notations? Example: 194.24.0.20/20 194.24.0.20/21 194.24.0.20/16 194.24.0.20/24 194.24.0.20/29 194.24.0.20/15 And so on... How will it ...
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1answer
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Why can my device not get an ip from DHCP in a network with 2 VLANS of which one has DHCP?

In our company we have a CISCO 2811 Switch accompanied by an HP1920 Switch. Our current configuration consists of 2 VLANS: VLAN-2 that has no DHCP in IP range 192.168.0.0/24 VLAN-5 That contains DHCP ...
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Possible typo in Tanenbaum's book about NAPT

From what I have understood from multiple sources (web and other books) about the concept of NAPT (also called NAT overload or IP masquerading in Linux environment), if there is a scenario like the ...
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what were the classless routing protocols used with VLSM when it was first introduced?

Since VSLM is supported only by classless routing protocols, if VSLM was introduced in 1987(RFC 1009) and all classless protocol(RIPv2 developed in 1993 , OSPF standardized in 1989 RFC 1131 ) cited ...

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