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Questions tagged [ipv4]

Use the ipv4 tag ONLY if the nature of your question specifically involves IPv4 addresses or networking -- often in contrast to IPv6. Most networking currently involves IPv4 addresses, so you should NOT include this tag with every networking question.

6
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3answers
24k views

SSH login via IPv6 successfull while using IPv4 to the same host yields “Permission denied”

I'm currently stumped by a strange problem… I have a dual stack host to which I want to SSH. If I connect via IPv6 everything works like expected datenwolf@foo ~/ > ssh -6 bar.example.com Password:...
1
vote
1answer
64 views

How can I get the ipv4 address from `ip link` like I used to see with ifconfig?

When I run ip to get the ip address, I'm getting $ ip link 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000 link/loopback 00:00:00:00:...
2
votes
1answer
76 views

How to connect to a IPv6 service using IPv4 connection on CentOS 7?

I'm trying to work out how to connect an inbound IPv4 connection to a port listening on a IPv6 port on a CentOS box. To demonstrate on a vanilla CentOS 7 server: Confirm bindV6only is disabled $...
2
votes
0answers
63 views

ntp using ipv6 address instead of ipv4

I have a laptop running a version of Linux ( 3.12 ). I have ntpd installed and configured to sync with time.google.com. The problem I am having is if I am plugged into a network that only provides ...
9
votes
0answers
1k views

curl request to IPv6 localhost gets stuck

A docker container of mine exposes a HTTP interface on port 8500, which is mapped to host port 8500. It is not IPv6 enabled. This still means, I should be able to access it at localhost:8500. IPv6 ...
0
votes
1answer
53 views

How do I use grep to output only the names of files that contain any ipv4 address

I am using Red Hat Enterprise 6 and I'm trying to search through the /etc/ directory for files that contain any IPv4 address.
0
votes
2answers
33 views

Do the default settings of NetworkManager detect if there is a conflicting IPv4 address on the network?

Added support for detecting duplicate IPv4 addresses, with a timeout configurable through the ipv4.dad-timeout connection property. -- NEWS dad-timeout / int32 / -1 Timeout in ...
1
vote
1answer
209 views

does :::80 in netstat output means only ipv6 or ipv6+ipv4?

If I am listening on :::80, is it listening on all ipv6 or all ipv6+ipv4? This is my netstat -tln: tcp 0 0 :::8080 :::*
0
votes
0answers
19 views

Getent Hosts For Port 1915/tcp -iptables

I have a scenario: i will have to protect my network from unsolicited access from my DMZ machine, configure node-A to allow new connections on port 1915/tcp from hosts (obtained by 'getent hosts node-...
-2
votes
1answer
26 views

Get Wireless LAN IPv4 Address Of Device

I want to know the easiest way and I would perfer a single line command that works on most or all Linux distros. I want to get the devices IPv4 address. The reason why I want to know this is because ...
1
vote
2answers
103 views

Execute Perl commands from a specific IP?

I have a Debian Jessie 8 server with three unique IPv4 IPs. I connect to the server from Windows 7 via Putty. I can open three Putty windows using each of the three IPs. I am trying to execute a Perl ...
1
vote
2answers
452 views

iptables limit the number of connections in the system for both ipv4 ipv6

A connection is a 5 tuple (ip src/dst, port src/dst, protocol). What about different connections between ipv4 and ipv6? If I define the iptables rule: iptables -A INPUT -p tcp -m connlimit --...
1
vote
0answers
25 views

Cannot connect with IPV4 servers [closed]

IPV6 works fine, but IPV4 does not. I can: resolve dns names just fine (dont think its an dns issue) I am connected to the AP correctly (dont think its a connectivity issue) I have a IP address (...
1
vote
3answers
66 views

How can check ipv4 address in shell. Like is it *.*.1.* or *.*.0.*?

So here I tried to get from the ifconfig file, but same with errors with simple ifconfig command !#/bin/sh if [/home/pi/ifconfig | grep -Eo ‘inet (addr:)?([0-9]*\.){3}[0-9]*’ | grep -Eo ‘([0-9]*\.){3}...
1
vote
2answers
10k views

Apache server not listening on IPv4 but listening on IPv6

We are facing one weird problem on one of our RHEL apache server. Actually, it is not listening on port 80 from remote hosts. When we locally browse http://localhost it is opening default page. When ...
2
votes
1answer
254 views

IPv4 and IPv6 sockets with same port

Is it possible to have a single process that would have two sockets, one using the AF_INET and one using the AF_INET6 families, while both being bound to the same port number, e.g. 20000? If the IPv6 ...
0
votes
0answers
24 views

Question about IPv4 when installing DragonFly latest/5.2.2

Someone told me to take a look at DragonFly BSD recently and I decided to take it for a spin. I downloaded the latest bzip'd ISO from their website and wired that ISO up to a VirtualBox VM. I checked ...
50
votes
4answers
24k views

Can TCP provide more than 65535 ports?

Is it possible to setup a Linux system so that it provides more than 65,535 ports? The intent would be to have more than 65k daemons listening on a given system. Clearly there are ports being used ...
2
votes
1answer
2k views

Loosing IPv4 and DHCP constantly asking for IP

Using Ubuntu 16.04, almost every day I'm loosing IPv4 address, being dropped by Avahi Daemon. Also, I see the DHCP is not "waiting" for leasing time to finish to request an address again, it does it ...
3
votes
1answer
833 views

What's ndisc_cache?

Suppose I want to use : $ ip ntable show dev eth0 inet arp_cache dev eth0 refcnt 4 reachable 20744 base_reachable 30000 retrans 1000 gc_stale 60000 delay_probe 5000 queue 31 ...
3
votes
4answers
24k views

Installing vsftpd - 500 OOPS: could not bind listening IPv4 socket?

I have to set up a FTP server on my machine. I have installed vsftpd using the command: sudo apt-get install vsftpd I then edited the configuration file vsftpd.conf in the location /etc. The file ...
1
vote
2answers
2k views

Using Linux as router with nftables - masquerade not forwarding reply back

I have a Linux machine which I'm using as a router. It has 5 network interfaces: three separate LANs which it routes between, and two WANs. At the moment I just have one WAN as the default route, and ...
3
votes
1answer
886 views

Debian and Centos: why does ipv6 prevail over ipv4

Every time I am configuring a Debian or Centos machine with a static IP address, I forget about that behavior of not taking in account my IPV4 configuration. Then, I search for the 1000th time the ...
0
votes
2answers
150 views

iptables blocks SSH connection

I've recently upgraded my Raspberry Pi from Raspbian 8 (Jessie) to 9 (Stretch). The Pi in accessible on my LAN both via IPv4 and IPv6. I have applied some iptables rules (IPv4 only) to block hosts ...
0
votes
1answer
49 views

IPv6 superuser ports

Does IPv6 have the 0-1024 superuser requirements for ports? I saw in the changelog for Linux 4.11 that they added a sysctl option to change it, but it only lists it under IPv4. Also does Open/FreeBSD ...
1
vote
0answers
54 views

iptables ipv4 configuration for OpenVPN Connectvity

I'm following this tutorial in order to setup my openvpn server: https://linode.com/docs/networking/vpn/set-up-a-hardened-openvpn-server/ When i reached the part to replace the ipv4 configuration, ...
2
votes
1answer
489 views

Why is BIND not automatically trying all nameservers, especially when an IPv6 nameserver is unreachable?

I am running a recursive local name server using BIND on Ubuntu. I have an IPv4 network at the moment. It appears as though BIND defaults to listen for queries and recursively resolve names on both ...
9
votes
9answers
3k views

Bash: Extract one of the four sections of an IPv4 address

We can use the syntax ${var##pattern} and ${var%%pattern} to extract the last and first section of an IPv4 address: IP=109.96.77.15 echo IP: $IP echo 'Extract the first section using ${var%%pattern}: ...
14
votes
2answers
43k views

Two interfaces, two addresses, two gateways?

I have a system that has two network interfaces with different IP adresses, both of which are in the public address range (albeit via NAT in the case of the first one) and both of which have different ...
6
votes
5answers
38k views

Can I prevent a default route being added when bringing up an interface?

I have a system with two NICs on it. This machine, and a few accompanying devices will be moved and attached to different LANs or sometimes it'll be using dial-up. eth0: - 10.x.x.x address ...
1
vote
1answer
2k views

IPv6 socket creation failed: Address family not supported by protocol

OS: GNU/Linux Debian 9.2 64-bit I disabled IPv6 on one of my servers. And now I'm getting this in mail: exim paniclog ... IPv6 socket creation failed: Address family not supported by protocol How ...
1
vote
0answers
272 views

SSH Tunnel broker over IPV4 for machines behind CNAT

I am not sure if I should be asking this in Unix & Linux or Network Engineering Here is the physical scenario [Host 1]----[Carrier-grade NAT]---->AWS<----[Carrier-grade NAT]----[Host 2] ...
1
vote
1answer
1k views

Not getting dynamic IP address by dhclient on a virtual Fedora

I run a course that includes practical classes on system administration. For that years ago I created a Fedora 20 virtual image -- it need not be a modern and secure one as it is only for executing ...
21
votes
2answers
32k views

netstat — why are IPv4 daemons listening to ports listed only in -A inet6?

I have a computer with: Linux superhost 3.2.0-4-amd64 #1 SMP Debian 3.2.60-1+deb7u3 x86_64 GNU/Linux It runs Apache on port 80 on all interfaces, and it does not show up in netstat -planA inet, ...
1
vote
1answer
561 views

Get DHCP running with Kernel 4.14-rc5

I tried to solve my problem that my touchpad is not running on my Lenovo 720-15IKB by installing the latest rc kernel 4.14.rc5 as described here, which really worked! The touchpad is working then! ...
3
votes
1answer
5k views

How do i check if DHCP is enabled?

I have a VM running Debian 9 and the latest version of VirtualBox. I have VirtualBox configured to use the bridged adapter and it was working fine yesterday. But when I came and got on it this morning....
0
votes
1answer
118 views

What is ICMP reply for all-zero host-bit IPv4 address?

We all know that the first address of any sub-net is network identifier and it can't be assigned to any hosts. For example in network 10.1.1.4/30, the address 10.1.1.4 is network identifier. If ...
1
vote
0answers
2k views

vsftpd works with ipv6 but not with ipv4

I am running an ftp server via vstfpd. /etc/vsftpd.conf: listen=YES #listen_ipv6=YES anonymous_enable=NO local_enable=YES write_enable=YES use_localtime=YES xferlog_enable=YES #...
1
vote
1answer
5k views

Change the listening address to IPv4 from IPv6

I use netstat -plnt check the vsftpd deamon, it is listening the IPv6(tcp6) address, so I use the FileZilla can not connect the VM. [root@localhost src]# netstat -plnt Active Internet connections (...
4
votes
1answer
4k views

wget uses ipv6 address and takes too long to complete

On a server wget-1.16 takes 8 minutes to complete: $ wget http://http.debian.net/debian/dists/stable/Release -O - --2017-06-12 23:44:40-- http://http.debian.net/debian/dists/stable/Release [...
0
votes
3answers
161 views

Find local processes starting TCP connections

With tcpdump I see many SYN packets ... and source IP is Localhost. I wish to find which processes are trying to connect. Note the connections don't reach ESTABLISHED state, they seems to be random ...
1
vote
1answer
494 views

Routing packets between IPv4 and IPv6 networks on different Interfaces

I have a Linux-Board with two Ethernet-Interfaces (eth0, eth1). On eth0 I have a IPv4 network, on eth1 there's a IPv6 network. Now I want to route packets from specific devices on the IPv4-network to ...
1
vote
1answer
771 views

Mapping IPv6 to IPv4 addresses

I'm trying to figure out what commands I can use to help me map IPv6 to IPv4 addresses on a local network. I would like to be able to do the operation both ways (IPv4 -> IPv6 and IPv6 -> IPv4) where ...
2
votes
1answer
8k views

Add IPv6 address to existing IPv4 interface not working

Probably a simple answer but I can't seem to find it. I am running a multihomed Debian Stable(latest) and on interface eth1 I need both IPv4 and IPv6 address. My /etc/network/interfaces looks like ...
0
votes
1answer
1k views

How does Linux choose between default gateways?

I have a computer with two NICS, one eth one wlan. wlan is on 10.0.0.0/24 eth is on 192.168.0.0/16 Kernel routing table is: $ route -n Kernel IP routing table Destination Gateway ...
3
votes
1answer
426 views

Can not resolve names but can ping addresses when connected to IPV4 router, all works fine with IPV6 router

At my place I have a router that gives me an IPV4 address. My Gentoo PC works fine but my Gentoo laptop stopped resolving names. I visited my parents and tried connecting to their router, which gives ...
1
vote
1answer
2k views

IPv6 over TCP or TCP6

My understanding is that tcp6 is used for connections over IPv6 & tcp is used for connections over IPv4. and ::ffff:127.0.0.1 is representing IPv6 address which is mapped to IPv4 address. ...
1
vote
1answer
2k views

Changing the port letsencrypt tries to connect on

So, one of my servers is behind NAT, and since there is already a publicly accessible apache server going on my LAN, I decided to access it from the outside with different ports, and remap them to the ...
2
votes
2answers
815 views

How does Debian select or prioritize IPv4 and IPv6 connections?

I'm going to explain my question with an example. I have two servers, A and B, both runs Debian 7.8, both have dual-stack connection to the Internet (I don't know if it matters but they even have the ...
0
votes
1answer
359 views

According to socket statistics Apache listens only on IPv6, but actually serves IPv4 as well

ss -lnp in server shows following information: # ss -lnp Recv-Q Send-Q Local Address:Port ...