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Questions tagged [loopback]

In TCP/IP a loopback device is a virtual network interface implemented in software only and not connected to any hardware, but which is fully integrated into the computer system's internal network infrastructure. Any traffic that a computer program sends to the loopback interface is immediately received on the same interface.

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What is the difference between Loopback Interface and Dummy Interface in Ubuntu 20.04

I would like to know whats the differences between loopback and dummy interfaces in Ubuntu and how they behave. Because when I assign /24 IP address on Loopback interface and route this range in my ...
Mesbah Ahmadi's user avatar
0 votes
2 answers
231 views

Using host loopback device into VMs

While deciding what IP address to assign to a local VM a question arose into my mind: why can't I just assign an address of the 127.0.0.0/8 net (so I can avoid any kind of IP clashing)? After all, it ...
Mega-X's user avatar
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Stop Nginx from listening on all loopback IPv4 addresses EXCEPT 127.0.0.1

On Ubuntu, Nginx apparently listens on all of the IPs in 127.0.0.0/8. How can I disable listening on 127.0.0.0 and 127.0.0.2–127.255.255.255? That is, the only IPv4 loopback address that I want Nginx ...
Ben Zelnick's user avatar
0 votes
0 answers
446 views

On Linux, how to send packets with local destination NOT through the loopback interface

I have a Linux server with two ethernet interfaces which are connected to the same switch and are in the same subnetwork. The topology is as following +--------------------+ | | | ...
Donlon's user avatar
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1 vote
1 answer
584 views

Is there a way to add multicast to loopback interface on a kubernetes pod?

Using an in-prem kubernetes installation on baremetal (Ubuntu) servers, installed with kubeadm. Kubernetes version is 1.25.3 Need to have multicast on a pod's loopback for the automated tests running, ...
Mikha's user avatar
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0 answers
229 views

Can Loopback IP be Public

I have a Usecase where an Access Device need to reach a Core Device over the Internet. Access Device is configured with the Public IP of the Core device as of now so that it can reach the Core over ...
Alex Philip's user avatar
-2 votes
1 answer
577 views

localhost loopback tcp connection in Windows: increase the bottleneck of 65535 bytes per segment

The scenario that I have is as such: I have a loopback TCP session and I want to improve its performance. I have my socket-like objects (System.Net.Sockets in .NET Framework, to be specific) sending ...
yu quan's user avatar
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661 views

Loopback connection seems blocked

Here is the situation i met: Server is managed by laravel forge It is serving behind cloudflare reverse proxy Nginx is up and running, listening on both port 80 and 443 (confirmed) now i need to ...
0nepeop1e's user avatar
0 votes
2 answers
379 views

Linux: Reserving a loopback port to a user with no authentication. Is this possible?

I want the user who starts the listening process on the port on the loopback interface to be the only user who can connect to this port. Reserving the port. No authentication. I want other users to be ...
David Diggles's user avatar
-2 votes
1 answer
176 views

Connectivity issues with 127.x.x.x series [closed]

Asked this in network-engineering in stack exchange and was redirected here. I have a couple of servers with the below config server1: eno1: 127.15.0.1/16 scope global eno2: 5.0.0.1/24 server2: lo: ...
RBK050's user avatar
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Windows firewall ipv6 loopback issue

I received it on my windows firewall log: DROP TCP ::1 ::1 53264 47001 I tried to add ipv6 ::1 or any other ipv6 loopback address to the firewall rule but received only the message below: An ...
Andro Leo's user avatar
2 votes
1 answer
4k views

Gigabit RJ45 loopback not working (100 Mbps ok)

I made myself a loop back plug as per When I plug it into a 1Gbps port on 100/1G switch the port does not light up. 100 Mbps port on 100 Mbps switch lights up no problem. The obvious problem could ...
user3280964's user avatar
0 votes
1 answer
596 views

What is the difference between the loopback interface and the 127.0.0.1 IP address?

I am trying to allow connections between softwares running on the same machine in iptables. The following kill my internet connectivity: # The following rules doesn't allow the VPN connection to be ...
robertspierre's user avatar
1 vote
1 answer
732 views

Does DPDK/RDMA between 2 machines gives lower latency than local host ping

I know loopback will go through the kernel network stack until reach IP layer, including syscall overhead and some memory copy overhead. DPDK and RDMA use different technology to avoid these. So let'...
Liang Mury's user avatar
1 vote
1 answer
385 views

How to assign an additional IP to loopback

I have a few docker containers which are supposed to access a shared PostgreSQL running on the Gentoo host. This works well if the dockerized apps connect to the database using the public IP of the ...
svoop's user avatar
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4 answers
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Is a loopback interface just another term for virtual interface?

I've been reading through many forums and many questions here on loopback interfaces and a point that is constantly iterated is that a loopback interface is a virtual interface. In hypervisors like ...
rsn's user avatar
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-1 votes
3 answers
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Forward packet from loopback interface based on routing table

I have a problem in which I need to process some packets and send out to more than one interface/network. My solution is to send the packet to a loopback/dummy interface and based on the Linux routing ...
Shihab Pullissery's user avatar
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0 answers
43 views

Can't track applications network communication under same machine

I have a network application environment of 7 applications communicating with eachother through UDP and TCP. All of them using either the machine's local network IP or 127.0.0.1 (localhost) to listen ...
underthevoid's user avatar
1 vote
1 answer
1k views

two tap device connect each other in same pc

What I want to implentent is something like below. 192.168.1.1 192.168.1.2 +--------+ +----------+ +-----------+ +---------+ ...
randomeval's user avatar
1 vote
2 answers
786 views

changing netmask of loopback interface

I can change netmask of loopback inteface (usually lo interface has 127.0.0.1/8): pi@raspberrypi:~ $ ifconfig lo: flags=73<UP,LOOPBACK,RUNNING> mtu 65536 inet 127.0.0.1 netmask 255.0.0.0 ...
mastupristi's user avatar
1 vote
0 answers
221 views

How can I capture traffic for a daemon listening on a cloned loopback IP address?

I have a daemon listening on a virtual IP address attached to a cloned loopback interface (lo1) on FreeBSD 11.x. Inbound traffic for that daemon could arrive on several different physical interfaces, ...
Alnitak's user avatar
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306 views

iptables loopback opens all ports

I have a strange problem with iptables and my loopback interface. ifconfig says: lo: flags=73<UP,LOOPBACK,RUNNING> mtu 65536 inet 127.0.0.1 netmask 255.0.0.0 inet6 ::1 ...
Tim Altgeld's user avatar
9 votes
2 answers
13k views

ssh -R binds to 127.0.0.1 only on remote

I'm running ssh -N -f -R127.0.2.3:23000:127.1.2.3:23000 user@remote , and I expect the tunnel on remote has opened on 127.0.2.3:23000, but it only opens on 127.0.0.1:23000, and it's inconvenient ...
Auxorro's user avatar
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0 answers
531 views

Loopback interfaces is not pinging on both pcs for packet tracer

I am trying to ping my isp ip address (aka loopback 1) and loopback 10 to PC1 and PC2. Whenever I ping both ip addresses and default gateway from pc1 to pc2 it works. However, when I'm trying to ping ...
Kevin 's user avatar
2 votes
2 answers
961 views

I have a loopback traffic in linux involving port 631 and I have no idea what is causing it

So I did some packet capturing in my networking and everything else is actually fine except for this weird communication where source and destination is literally 127.0.0.1, source port is 631, and ...
cmakeislife's user avatar
1 vote
0 answers
256 views

Loopback adapter cannot connect to the domain network

I am working on a project creating Microsoft Print Server Farms with High-availability. It works perfectly with the Loopback adapters in the servers and a network load-balancer. The Loopback adapters ...
Howard2119's user avatar
1 vote
1 answer
158 views

Calculate pm2 ram consumption on basis of hit or traffic

I have deployed loopback backend application in ec2 instance. I am using Pm2 server. How can I calculate ram and cpu for traffic or hit ?
MD. Ashfaqur Rahman Tahashin's user avatar
2 votes
1 answer
2k views

IP Address is very slow compared to loopback address

I have an AWS EC2 VM. I want to run a bunch of scripts on a PostgreSQL server hosted on the same machine. When I use the IP address of the server in scripts, it took almost 5 seconds per script. But ...
YogeshR's user avatar
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1 vote
2 answers
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Network loopback device missing in Ubuntu 14.04

I want to program an FPGA via JTAG and the xmd script connects to 127.0.0.1:3121 to do so. That worked nicely for months. After a reboot this connection suddenly didn't exist any more, I cannot ping ...
Martin's user avatar
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3 votes
1 answer
6k views

Add-NetNatStaticMapping not port forwarding to local VM

I'm running windows 10 build 1809 and have hyper-v installed. I have a Linux machine running behind a NAT with internet connectivity working on IP 10.0.5.5. I basically followed instructions on the ...
Mark's user avatar
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2 votes
0 answers
41 views

Does Loopback able to support all TCP/IP protocols

Does a Windows loopback adapter supports ACD and duplicate IPs. Say we have a code that supports full TCP stack and we bridge the program to loopback using PCAP. If in case I set both the address ...
Programmer's user avatar
0 votes
1 answer
727 views

How can I count / view all fast-path sockets on windows server?

In case you're not familiar, fast path loopback sockets: https://blogs.technet.microsoft.com/wincat/2012/12/05/fast-tcp-loopback-performance-and-low-latency-with-windows-server-2012-tcp-loopback-fast-...
Ronen Ness's user avatar
0 votes
2 answers
1k views

Windows Loopback adapter not participating in local network

I have created a Windows loop back adapter with 'Obtain IP address Automatically' enabled. ipconfig /all Ethernet adapter LL Address: Connection-specific DNS Suffix . : Description . . . . ....
Programmer's user avatar
1 vote
1 answer
1k views

ip command equivalent to `ifconfig lo x.x.x.x up`

I am trying to set bind loopback to an IP address with ip link set lo 10.254.254.254 up but keep getting the error Error: either "dev" is duplicate, or "10.254.254.254" is a garbage. I googled the ...
dhuyvetter's user avatar
2 votes
1 answer
643 views

Corosync cluster will not bind vips to loopback, so apache fails to start in CentOS 7

I have a problem getting apache to work in a corosync cluster. I probably sifted through more than hundred web pages and a couple of dozen Google Searches, and was not able to find any matching ...
Rudy's user avatar
  • 21
3 votes
1 answer
3k views

How can I give access to loopback devices which are created dynamically to a Docker container?

I have a small Docker container from which I can access /dev/loop0. For this I've added to docker run: --device=/dev/loop-control:/dev/loop-control \ --device=/dev/loop0:/dev/loop0 \ On this ...
emmerich's user avatar
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1 vote
1 answer
5k views

Add second ip to loopback on Centos

We currently run Suse servers and add the following to the loopback interface: vi /etc/sysconfig/network/ifcfg-lo # Loopback (lo) configuration IPADDR=127.0.0.1/8 IPADDR_2=192.168.0.91/32 NETMASK=...
rezizter's user avatar
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-1 votes
1 answer
1k views

Nat Loopback - Access external IP from internal

I have a static IP and I've made a webserver that is running fine from WAN (domain points to my IP). However, when I access my external IP/Domain from my LAN, it redirects me to my router login page. ...
Turbo's user avatar
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-1 votes
1 answer
4k views

Err-disable in Switch 2960 [closed]

I have a problem. I have a Cisco 2960, this switch conect 23 Macs. The problem is that a pc puts the port in err-disable. When I put the command "show interfaces status err-disabled" the output is ...
Joshua HG's user avatar
0 votes
0 answers
27 views

Kubuntu 17.04 on VM: loopback interface routed "outside"

Disclaimer: Yes, I know my problem description might be not very accurate and my terminology as well. Can not change that since I am new to this topic and do not know it yet. But I apprechiate ...
Michael's user avatar
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-1 votes
1 answer
794 views

How to change loopback network mask or redirect subnet to another interface [closed]

I have the following problem. First of all. Here are my interfaces. # ip addr ip addr 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue state UNKNOWN link/loopback 00:00:00:00:00:00 brd ...
e109848's user avatar
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1 vote
0 answers
216 views

A looped hub connected to a switch

---- We don't want to block the use of Hubs --- If two switches are connected to each other via a hub, STP detects and blocks alternate link (if available). But if a hub is connected to even one (...
Nurhak Altin's user avatar
1 vote
2 answers
6k views

iptables dnat not working for https

I have an http server listening on ports 8080 (http) and 8081 (https) on 127.0.0.1 I have these iptables rules to redirect from/to $external_ip: iptables -t nat -A PREROUTING -i eno1 -p tcp -d $...
morgano's user avatar
  • 123
3 votes
2 answers
3k views

Heavy TCP traffic on loopback

While trying to generate some test traffic on my loopback interface, I noticed there was so much noise there that the output from Wireshark was essentially useless, with tons of SYN/RST, ACK packets ...
Guilherme's user avatar
  • 133
1 vote
2 answers
4k views

Why adding external IPs to loopback (lo) works just like adding to ethX

For ages(>7yr) my automation scripts were adding new external IPs to the servers in this way ifconfig lo:0 11.22.99.44 netmask 255.255.255.255 ifconfig lo:1 11.22.33.44 netmask 255.255.255.255 ......
Alexander lazutov's user avatar
3 votes
2 answers
12k views

How do I force localhost resolution to be 127.0.0.1 instead of ::1?

I'm running Windows 10 x64 and I have a legacy application that doens't work fine with localhost being translated to ::1, but instead it works for 127.0.0.1. How do I force Windows 10 to resolve ...
gremo's user avatar
  • 349
2 votes
0 answers
432 views

TCP packets dropped in ipv6 loopback

Just logged in to a Windows host, I noticed an unexpected CPU usage. I quickly found out the processor was being hogged by the Windows firewall services. I enabled logging, and I started to see ...
aledeniz's user avatar
  • 213
1 vote
2 answers
121 views

using ethernet ipv4 as internal bus while allowing the full ipv4 address range for the external interface

We have designed a device to be used as one device, but using ethernet ipv4 inside to communicate with internal not linux-based ipv4-speaking peripherals, juste like what we could do using pci or usb, ...
Philippe De Muyter's user avatar
3 votes
1 answer
4k views

Is it important to use localhost/127.0.0.1 rather than machine's own IP address?

I'm on Amazon AWS EC2 running Amazon Linux, though that may not be significant to the answer. Say I have three hosts, H1, H2, H3, with private IP addresses of 10.0.0.1, 10.0.0.2, and 10.0.0.3. This ...
sootsnoot's user avatar
  • 425
1 vote
1 answer
1k views

Ubuntu rename loopback interface

I have a Linux box with Ubuntu 16.04. I've noticed some odd behavior when I needed use the loopback interface. So I checked with ifconfig first and it showed that: rename1 Link encap:Local ...
northway's user avatar