Stack Exchange Network

Stack Exchange network consists of 174 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

Questions tagged [ipv4]

Refers to the 4th revision of the Internet Protocol, where addresses are usually displayed in the form of dotted decimals between 0-255. Ex: 169.254.0.1

0
votes
1answer
20 views

VPN Router does not reply to ARP Requests

So i have these three network interfaces setup on a linux box: eth0 is facing the external network (192.168.1.0/24) tun0 is the vpn interface (10.8.8.0/24) eth1 is the local network interface (...
24
votes
1answer
3k views

Should my website have an IPv6 address?

My website only has an IPv4 address. With IPv6 being the future, is it possible that some users may not be able to reach the website if it does not have an IPv6 address? Also, does having an IPv4/IPv6 ...
0
votes
0answers
22 views

How to tunnel an IPv6 website through an IPv4 in a VPS? [duplicate]

My ISP will only let me host things in IPv6. I'm hosting an IPv6 http page and need people with IPv4 connection to access it. I have a VPS which can be used to grab the IPv6 page and return as an IPv4 ...
0
votes
0answers
3 views

Using Fritz!Box 3490 to forward external traffic to internal servers [migrated]

I have a Fritz!Box 3490 along with 5 usable external IPv4 addresses provided by our ISP. The Fritz!Box is to replace our existing DrayTek 2925. One of five IP addresses is an MX; so we use that IP to ...
0
votes
0answers
29 views

Differences between IPV4 to IPV6 transition methods

After some research, I found 3 main methods in order to establish the transition from IPV4 to IPV6, Dual Stack Tunneling Translation Now, I can understand them all and how they work, but very few ...
1
vote
1answer
61 views

IPv4 identification field manipulation in linux

When Don't Fragment flag is set, IPv4 RFC allows set Identification filed to 0x0000. I got a peer which is behind firewall that brakes RFC and block any IPv4 packets with such 0x0000 ID field. My "...
0
votes
1answer
46 views

Dualstack support for IGMP multicast NLB on Windows 2016

I have two Windows 2016 VMs set up as an NLB cluster. Each guest has two interfaces, one of which is for the NLB, the other for other traffic. I've added an IPv4 and an IPv6 address to the cluster. ...
0
votes
0answers
22 views

SG300 switch doesn't have IPv4 Interface configuration [on hold]

We purchased two SG300 switches. They have same firmware version. One of them has IPv4 Interface configuration and everything is ok. But in the other switch I can't find the IPv4 Interface ...
0
votes
1answer
91 views

Ubuntu defaults to IPv6, should default to IPv4

Ubuntu 16.04.5 with kernel 4.4 used to work as intended: IPv4 is default. Since changing to kernel (hwe) 4.15, it uses IPv6 as default. It has IPv6 available via Tunnelbroker, broadcasted by the ...
0
votes
1answer
169 views

Problems with DNS and IPv6 on Server 2012 and 2016

I manage hundreds of servers for many customers. Most are SMB segment, having 1 to 3 servers per customer max. In past few weeks I get more and more frequent DNS errors on random domain controllers, ...
0
votes
0answers
50 views

Is the Inside Global IP address the same as the Public IP Address? [NAT TABLES, Public IP, Private IP, Inside Global Address]

Is the Inside Global IP address the same as the Public IP address? Private IP addresses assigned to each device are translated using NAT to a Public address. Is that public address the same as the ...
0
votes
0answers
116 views

Sending mail with ssmtp over IPv4

Apparently DigitalOcean blocks outbound SMTP on IPv6. I can confirm this with telnet as follows: ⟫ telnet smtp.gmail.com 465 Trying 2607:f8b0:400d:c07::6c... > Waits for about 2 minutes ...
0
votes
1answer
81 views

How to use subnet-zero ip address in practice?

I know that subnet-zero ip address refers to a subnet itself, while subnet-one ip address is used for broadcasting. How can we use subnet-zero ip address? Does any router have a capability to make ...
0
votes
1answer
260 views

Route IPv6 traffic through IPv4 tunnel

My current situatuion is that i want to use IPv6 but currently don't have any IPv6 address assigned. But I have a server with a dual stack interface including a public IPv4 and IPv6 address (only a /...
0
votes
1answer
42 views

Filter traffic from IPv4 to IPv6 and vice versa

I've tried to filter (using nftables, but I'm open for a change if it works using iptables) traffic coming from an IPv4 network to an IPv6 network, but can't figure out how to do it. Suppose I have a ...
-1
votes
1answer
60 views

IPTables NAT Ubuntu redirect 2nd IP to another IP

i have got two servers : Server 1: IP1= 8.8.8.1 IP2= 8.8.8.2 Server 2: IP1= 8.8.8.3 i want to redirect every access to IP 8.8.8.2 to 8.8.8.3. Therefor I activated IP forward sysctl net.ipv4....
0
votes
0answers
299 views

squid proxy - use ipv6 only for outgoing traffic

I want to set up a squid proxy to use ipv6 only for outgoing traffic. I want the ip4 address to be totally invisible to the service I connecting to. I don't care about fallback and lack of ipv6 ...
-1
votes
1answer
722 views

Cannot ping 'server' after it reboots, how can I fix this?

The company I work for is using a Dell OptiPlex Micro PC (running Windows 10 Pro) as a server for some intranet resources (MS SQL Server databases and network licenses for some software). It also ...
0
votes
2answers
563 views

How to know if the server application is listening on ipv6

In a VPS (webfaction) I opened a port 14152 and I am running an application which is listening connections on that port, this is the output of netstat -putan | grep 14152 udp6 0 0 :::14152 ...
0
votes
2answers
2k views

Nginx keeps throwing nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)

I have been checking plenty of websites, and many questions/answer here in ServerFault about this issue. However, I don't seem to be getting into the root of the configuration error. I have 4 domains ...
0
votes
1answer
859 views

What IP addresses are included in a subnet “range”?

I'd like some help understanding subnets (CIDR). I'm using a tool to check if an IP is in an acceptable range given a CIDR address. When I input an IP address (12.245.105.190) and check it against ...
0
votes
1answer
38 views

How do I talk to a machine with the same IP as me but on a different subnet?

Suppose I am on one subnet and I want to send a message to another machine on a sibling subnet that has the same IP address as me. What is the syntax, conceptually and practically, to get my message ...
19
votes
4answers
6k views

What makes a private IP address not routable?

I understand that private addresses such as 10.0.0.0/8,172.16.0.0/12 and 192.168.0.0/16 are not routable. However, what exactly is stopping these addresses from being routable? Do ISPs implement ACLs ...
161
votes
10answers
30k views

How bad is IPv4 address exhaustion really?

For years the press has been writing about the problem that there are now very few IPv4 addresses available. But on the other hand, I'm using a server hosting company which gladly gives out public ...
-1
votes
2answers
52 views

AD client won't getIP address from DHCP server

Server is running Windows Server 2016. Client has Windows 8. Unless my client has a static IP address, it cannot communicate with the AD. My DHCP server won't give my client an IP addresses, and I don'...
0
votes
2answers
112 views

In the routing decision, why is only the source's subnet mask used and applied to both source IP and destination IP?

A subnet mask defines how an IPv4 address is broken up. IPv4 addresses nnn.nnn.nnn.nnn aren't like MAC addresses in that they are just random numbers. That defeats the purpose of Routing. They have ...
0
votes
0answers
44 views

ICMP Redirect Packet Sequence

I have one observation which i can't explain to others regarding icmp redirect. I have added a network route to host H1 for destination D1 for icmp redirect through redirect router R2. As usual, host ...
1
vote
0answers
445 views

Mikrotik port forwarding - no access to server

I need your help concerning port forwarding with Mikrotik's RouterOS! I have executed this command : /ip firewall nat add action=dst-nat chain=dstnat comment="Owncloud in NAT" dst-port=8079 in-...
1
vote
0answers
96 views

Postfix HELO on dualstack ipv4/ipv6

I have a postfix on dual stack ipv4/ipv6 server. V4 address is private (NATed to public V4). V6 address is public. Puclic V4 and V6 addresses have different PTR. 10.0.3.12 - NATed to 212.XX.XX.22 (...
5
votes
1answer
1k views

Can the network still work when DNS & DHCP go offline?

In my LAN I have a Windows server and a Synology NAS for storage, directly attached to the server and provided as storage to the clients through a VM. The server provides the domain controller, the ...
1
vote
1answer
491 views

Disadvantage of disabling IPv6?

Given that I have a dedicated public IPv4 address for a web server (Ubuntu). What are the real disadvantages of disabling IPv6 for our users?
4
votes
3answers
73 views

Some questions about xenserver HA

To start thank you for your future help :) I would like to know if it is possible to wrap my H.A as on my paint (excused me the quality of the drawing). I would also like to know how it goes with ...
11
votes
2answers
5k views

Difference between 0.0.0.0/0 and ::/0 in access control lists

When setting up access control lists, what's the difference between 0.0.0.0/0 and ::/0? I'm seeing this for an AWS EC2 instance I'm setting up
5
votes
1answer
774 views

Carrier Grade NAT concepts: IP bans

I'd like to deploy a Wireless WAN using IPV6 for at least the wireless bits given that 6 offers higher through-put. I'm exploring the concept of CGN and what strikes me immediately is the liability. ...
0
votes
1answer
206 views

postfix still using ipv6 even if inet_protocols=ipv4

I have set this in /etc/postfix/main.cf: inet_protocols=ipv4 #I also tried with smtp_address_preference=ipv4 But still, the received message in Gmail shows an IPV6 address next to SPF. ...
0
votes
0answers
23 views

IP internet service rejects API request from a single address

I am looking for several days now for an answer to following issue. I am having a web based API request, which works find on all of the tested internet connections (about more than 10) EXCEPT one. I ...
0
votes
0answers
237 views

website not working over IPv6 ISP

I have domain example.com which is hosted over window server 2012 R2, IIS 8.5. My web server is IPv6 enabled, online tools are able to resolve my domain over both IPv4 and IPv6, My website is ...
0
votes
2answers
56 views

Add data validation to IP address settings so that user is prompted if IP addresses are configured in same subnet [closed]

I am supposed to add validations to my software UI (IP Subnet UI) which allows the user to enter a pair of IP addresses and subnet masks. I am supposed to make sure that two network interfaces are ...
1
vote
1answer
106 views

drbd with IPv4 fallback

I was setting up DRBD over IPv6, I want to ask if it is possible to provide both IPv4 and IPv6 addresses in address section like below. on server1 { disk /dev/sdb1; address 140.X.X.X:7788; ...
0
votes
1answer
32 views

IPAM (IP address management) [duplicate]

Could any one please explain the difference between Splitting and Allocation a IP address block. Say if I have 10.0.0.0/24 (254 hosts) available. My requirement is to get a /25. Could anyone explain ...
1
vote
1answer
50 views

Block Clients based on RTT

I am running an application on my Debian server, which uses IPv4 and UDP for data communication. I would like to block every client for a short while, that has a Round Trip Time above 140ms. ...
0
votes
1answer
139 views

eth0-wlan0 brouter bridging IPv6, not forwarding/bridging IPv4, with DHCPv4 client *and* server

Please note: this is not the already-answered "IPv6 bridging+IPv4 NATing" question, but instead a "IPv6 bridging+DHCPv4 client on eth0+DHCPv4 server on wlan0" question. For IPv4/IPv6 Dual Stack and ...
2
votes
2answers
642 views

Access IPv6 server behind router with IPv4

An IPv4 client in Germany should access an IPv6 server in the USA. This server is in a private home with a common home-router. If it was an IPv4 server, I would just configure NAT and port forwarding ...
-5
votes
1answer
40 views

How can I appear to be coming from a certain IP address? [closed]

I have a friends IP and I want to appear to be coming from his specific IP to the outside world. How can I do that besides actually taking over his computer? Thanks!
-1
votes
1answer
364 views

How to do Fixed length subnetting? [duplicate]

This was an exam question last year, and I was trying to figure out how to get the answer: A small company is assigned the class C network 205.67.35.0. You need to divide this network to provide ...
1
vote
1answer
2k views

IPv4 to IPv6 proxy/passthrough

I recently had an app rejected from the ios store for crashing during their (now) mandatory IPv6 test (didn't even know they did that). My server (on AWS) wasn't setup for IPv6, but I've fixed that ...
2
votes
0answers
148 views

IPv6 connectivity through IPv4 using OpenVPN

I've set up a Debian-based server at home, which handles dhcp and a bunch of other services. Unfortunately, even though the machine is capable of using IPv6, my ISP doesn't support it. I was wondering ...
1
vote
2answers
383 views

IPv6 Webserver reachable for IPv4 only Clients

I have a web server with a public IPv4 address. For this IPv4 address, I have a DNS A record for "domainA.com". Since more IPv4 addresses cost money at my hosting company, I am thinking about using a ...
-1
votes
1answer
304 views

Ip4 and Ipv6 Default Gateway

We occasionally restrict internet access on some of our test servers by just quickly removing the default gateway. With the introduction of Windows Server 2016 we decided to test a few of its features ...
3
votes
0answers
2k views

Configure BIND to prefer IPv4 without disabling IPv6

Our office network is internally dual-stack, but the connection to the rest of the Internet is IPv4-only. I've got BIND 9.9 set up on a Linux box to handle DNS resolution. Is there a way to ...