Questions tagged [loopback]

This tag is for questions about loopback interfaces on network devices. For instance, you want to configure routing on your layer 3 switch and for that you want to configure a loopback interface.

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How to receive UDP packet with 127.0.0.0/8 dst address in userspace

I would like to know if it is possible in linux to receive an UDP packet in userspace that has a 127.0.0.0/8 dst address but coming from an external interface. I tested it with nc and I can see ...
zskr's user avatar
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42 views

How to make a loopback device appear and behave as a (removable) block device?

If I create a loopback device, I can mount it manually, but it doesn't show up in Plasma "Disks & Devices" as a newly attached Storage Volume (Removable Media), nor does it appear as an ...
mo FEAR's user avatar
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Why doesn't accessing /dev/loopX raw update correctly (in real-time) when contents are modified?

If I create a file, such as /tmp/vdev (400KB in size and formatted to ext4) then map it to /dev/loop18, and then mount the /dev/loop18 to /tmp/mnt, and then create a text file under /tmp/mnt and write ...
mo FEAR's user avatar
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1 answer
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Cannot login normally after login loop

I recently had a login loop that kept sending me back to the login screen no matter how many times I entered the correct password. I decided to login accessing the terminal directly by pressing cntrl+...
Ash's user avatar
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1 answer
667 views

how can I create additional loopback interface permanentely?

I can use ip addr add 130.100.0.5/32 dev lo to create a loopback interface. However, if I use /etc/sysconfig/network-scripts/ifcfg-lo to config it, it doesn't show up: DEVICE=lo IPADDR=130.100.0.5 ...
Wang's user avatar
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1 answer
261 views

Service only listens on 127.0.0.1 port 1025. How do you allow any computer on your local network to communicate with this service?

Let me open by saying I have scoured the internet, even companies I purchased the software from and it's been 5 months!! So I am turning to the community as my eyes and brain are bleeding from reading ...
Frank's user avatar
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137 views

Packets are unexpectedly routed to local lo interface

I have a question about routing between different network devices within the same Linux host: I created a Geneve network device (and this example is not related to Geneve tunnel; it's just that I ...
Howard  Yu's user avatar
1 vote
0 answers
267 views

ssh port forwarding, who has access to localhost?

I've done an ssh remote port forwarding: [email protected]% ssh -R 127.0.0.1:11999:host2.a.com:99 [email protected] My understanding is that this creates a TCP socket on host3.b.com's localhost port 11999. ...
Wandering Logic's user avatar
0 votes
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102 views

Why is my loopback interface losing its address sporadically?

After I upgraded to Fedora Linux 36 from 34 (first to 35) I'm getting an issue I had not faced before. The lo interface is losing its inet address and that's causing issues with programs that make ...
Aspiring Dev's user avatar
2 votes
1 answer
532 views

ipv6 multicast fails when it should loop back to self

So far I use multicast with ipv4 and it works; all involved computers run linux. I listen on two machines and send on one of those two (in a separate terminal). In the below example 'Hello 1' is ...
Al_'s user avatar
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4 votes
1 answer
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Why does tc-netem on loopback also affects other interfaces?

I'm trying to modify the network behaviour of my server(s), to simulate external/WAN connection behaviours (what ever that means). After doing tc qdisc add dev lo root netem delay 100ms, I can ...
renyuneyun's user avatar
1 vote
0 answers
201 views

My computer resolves itself to 127.0.0.1 instead of its outer ip

I recently installed dnsmasq in two of my machines. The service works all right but the trouble is that when consulted they return only their loopback ip. @Machina ~]$ nslookup continua continua ...
Lerian Acosenossa's user avatar
1 vote
0 answers
177 views

dummy_hcd loopback webcam. Impossible?

I've been trying to create a loopback USB Webcam device with the help of dummy_hcd kernel module. Steps I've taken: I load libcomposite via modprobe libcomposite. Then I load dummy_hcd via modprobe ...
winwin's user avatar
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2 votes
1 answer
4k views

How to make a loopback device writable for normal user?

I setup a loopback device following this guide. The device is OK, but only writable for root. I searched solutions and found some answer such as using fusermount, fstab etc., e.g. this one. I would ...
xrfang's user avatar
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0 answers
216 views

How to get my Pi zero audio simultanusly on my hifiberry and on ffmpeg?

Hope you can help me. Got a Pi Zero and Hifiberry Module playing with raspoitify. Speaker sound is fine. My goal is to have the same (raspotify) audio on a ffmpeg stream from that Pi as well. I ...
Krautmaster's user avatar
1 vote
0 answers
1k views

How to filter (rate-limit) traffic through a bridge, using nftables, depending on whether or not the traffic originated locally?

I'd appreciate some help with understanding how traffic filtering in a bridge works, especially for packets / Ethernet frames which originated locally. To explain the problem, I'll shortly describe ...
Binarus's user avatar
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1 answer
1k views

reordered and duplicated packets when using UDP over loopback interface

We are seeing UDP packets being reordered and duplicated when being sent over lo. We can see this because we're sending MPEG transport streams, which have their own sequence number in their headers, ...
Nathan Commons's user avatar
0 votes
0 answers
114 views

Pinging a shut down loopback interface from another system

We have two device R1 and R2 running FreeBSD 9.2, on R1 we have set an ipv4 address for lo1: R1#: sudo ifconfig lo1 192.168.80.80 Then add a route to R1 in R2: R2#: sudo ip r add 192.168.80.80 via ...
SAMPro's user avatar
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3 votes
2 answers
2k views

Manipulate filesystem image files without loopback devices?

I am trying to automate the creation of Raspberry Pi images under Docker virtual machine to run it in common CI systems like bitbucket-pipelines. On physical system I am using "template" ...
Dims's user avatar
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-1 votes
1 answer
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i need to display Number of RX packets and the number of TX packets for the loopback interface [closed]

im new to linux and i need to display Number of RX packets and the number of TX packets for the loopback interface. i have tried using ipcongif but for reason i get an error, im using ubuntu for ...
FF H's user avatar
  • 9
4 votes
1 answer
328 views

Virtual ALSA device, sync / intercept volume commands

I have a stereo. I like it, because the sound is nice, but it's not quite sophisticated engineered: It has an internal USB Card soldered on some board, directly outputting audio to the power amp. ...
dersimn's user avatar
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1 answer
125 views

IPv4 iptables blocks things, but output policy is ACCEPT, what is the problem with my INPUT DROP chain?

This is my IPv4 iptables list at this moment: Chain INPUT (policy DROP) target prot opt source destination ACCEPT all -- anywhere anywhere ctstate ...
orig's user avatar
  • 3
2 votes
2 answers
5k views

redirect external request to localhost with iptables

I have a service running on "localhost" address on a certain X port. Unfortunately, I can't change the address to "0.0.0.0" to expose that service. Can I use iptables to internally redirect request ...
Andrean's user avatar
  • 141
1 vote
0 answers
1k views

Does the loopback network inside the docker container shares host network loopback?

I recently faced issue with one client application which is running inside a container. This client making network connections to a server residing in the same container over loopback IP 127.0.0.1. ...
praveen raja's user avatar
1 vote
0 answers
698 views

retransmissions/out-of-order packets with large (~1 MB) writes/reads w/ TCP (SOCK_STREAM) over localhost loopback -- ACK lost

I'm seeing retransmissions/out-of-order packets when using the loopback interface and have been googling for days to try to determine if I should be surprised by this (which I am) or if anyone else is ...
R.Rex's user avatar
  • 11
0 votes
1 answer
77 views

How Can I Route A WAN IP Request To My Loopback Address And Port?

I have two virtual machines on my laptop. One of virtual machines want to reach an IP address (I have the IP) and I want to route this request to another virtual machine's port. I changed the default ...
WWA's user avatar
  • 1
0 votes
1 answer
143 views

traffic going through lo interface checking every 4 ports

I have noticed that there' s always traffic going on on my loopback interface. It's not a lot but I don't know where it's coming from and I'd like to stop it. There's syn request going from port X to ...
eftshift0's user avatar
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0 votes
1 answer
279 views

Understanding Netplan / NIC [closed]

I have a set of 5 static ip addresses. Currently I only have 1 server, so I want to route 2 static IP's to the same server. At the same time I still want the server to be part of the local network. ...
David Torrey's user avatar
0 votes
1 answer
622 views

Can't ping all the loop back addresses

As we know, the range for loopback addresses is 127.0.0.0 – 127.255.255.255. On my Linux box, I am able to ping all the addresses like 127.0.0.1, 127.0.0.2, 127.0.0.254, etc. (i.e., all addresses from ...
gu2004's user avatar
  • 3
0 votes
1 answer
466 views

Traffic into lo vs eth, why might I be seeing only half the traffic on lo compared to eth?

I am forwarding traffic to ports on eth0 and lo. For the same traffic at the same ports and different ports, when I do a tcpdump and count the packets, for time t, I only see about half the number of ...
Dave's user avatar
  • 103
1 vote
0 answers
313 views

IPv6: Why ping to another IPv6 host doesn't work when loopback interface is DOWN

While it is said the only job of lo interface is to test its own connectivity, why doesn't pinging another IPv6 host work when the lo interface is made DOWN. Network configuration: host1(eth0) - ...
SuprMan's user avatar
  • 11
1 vote
2 answers
53 views

How I manupulate these files in terminal at the same time

I have 139 different tab-delimited .txt files. I want to add a column to each file containing the name of that .txt file and finally attached all .txt files in one file; Let's say I have A.txt, B.txt, ...
Zizogolu's user avatar
  • 171
1 vote
1 answer
2k views

ALSA Loopback not recording system audio on Xubuntu 18.04 in ffmpeg command

I have an ffmpeg script to do my screencasts. I have Debian 9 at the office and Xubuntu 18.04 at home. On those two operating systems, the following works to record system audio and from my microphone....
jbrock's user avatar
  • 1,151
1 vote
0 answers
660 views

Alsa snd-aloop: add more loopback subdevices?

I'm currently working on a project on which I need to create multiple audio streams using snd-aloop. The issue is that we reach the max number of substreams easily. Is it possible to have more than 8 ...
Salma raiss's user avatar
1 vote
0 answers
129 views

New loopback device module does not show trace in wireshark

I am trying to write a network device driver that can duplicate the functionality of the loopback device. I modified the code available at the link. I am testing on Linux 4.8. I removed code related ...
Jake's user avatar
  • 1,363
0 votes
1 answer
573 views

Reachability of custom loopback interface on different machine

I have a loopback interface on one machine with a certain IP address, and on another machine I have a static route to that loopback interface subnet. I can ping the other loopback interface when ...
Eloy's user avatar
  • 137
2 votes
0 answers
76 views

selinux restorecon on systems without selinux like ubuntu [duplicate]

recently i had to change two files on a fedora raw image mounted via loopback on ubuntu, which usually runs in a kvm on the ubuntu host. That made a lot of troubles with selinux after booting from the ...
Mandragor's user avatar
  • 1,060
1 vote
1 answer
579 views

Linux audio loopback: Multichannel to stereo (for OBS usage)

I am using the RME Fireface 802 to record a stereo signal for my stream, but unfortunatly OBS won't accept Multichannel audio that contains more than 8 signals. So, since OBS doesn't like my ...
MDG Technik's user avatar
1 vote
1 answer
4k views

Does `lo` have no MAC address?

From https://networkengineering.stackexchange.com/questions/57935/is-a-network-interface-supposed-to-have-no-more-than-one-mac-address/57937?noredirect=1#comment100988_57937 A network interface in ...
Tim's user avatar
  • 102k
7 votes
4 answers
2k views

why `nmap 192.168.1.97` returns less services than `nmap 127.0.0.1`? [duplicate]

According to https://networkengineering.stackexchange.com/a/57909/, a packet sent to 192.168.1.97 "doesn't leave the host but is treated like a packet received from the network, addressed to 192.168.1....
Tim's user avatar
  • 102k
9 votes
1 answer
2k views

How come one can successfully ping 127.0.0.2 on Linux?

On a FreeBSD system with a loopback network interface … % ifconfig lo0 lo0 link up loopback drv_running running multicast nd6 performnud auto_linklocal no_radr link rxcsum ...
JdeBP's user avatar
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0 votes
2 answers
334 views

What does the action "loop back" mean? [closed]

I have some difficulty to picture a diagram for the meaning of loopback. https://en.wikipedia.org/wiki/Loopback#Virtual_loopback_interface Any traffic that a computer program sends to a loopback IP ...
Tim's user avatar
  • 102k
0 votes
2 answers
1k views

Are the IPv4 and IPv6 networks for my loopback interface the same network?

In output of ifconfig: lo: flags=73<UP,LOOPBACK,RUNNING> mtu 65536 inet 127.0.0.1 netmask 255.0.0.0 inet6 ::1 prefixlen 128 scopeid 0x10<host> loop txqueuelen ...
Tim's user avatar
  • 102k
1 vote
2 answers
388 views

Why is some virtual network interface assigned private IP address, while some is assigned loopback IP address?

Are docker0, lo and virbr0 are virtual network interfaces? Why are docker0 and virbr0 assigned private not loopback IP address? If private IP address can work like a loopback address, can lo be ...
Tim's user avatar
  • 102k
1 vote
0 answers
1k views

Trying to make loopback device as Alsa-to-Jack bridge

Using this guide i trying to make loopback device as Alsa-to-Jack bridge. Everything fine until those lines # capture client alsa_in -j cloop -dcloop # playback client alsa_out -j ploop -dploop On ...
asdjabka92's user avatar
0 votes
1 answer
158 views

Does "loopback" in a loopback file mean the same as in loopback IP address?

man pvcreate says pvcreate initializes a PV so that it is recognized as belonging to LVM, and allows the PV to be used in a VG. A PV can be a disk partition, whole disk, meta device, or loopback ...
Tim's user avatar
  • 102k
0 votes
4 answers
10k views

How can I do a loopback test?

Book Computer Networks says all addresses of the form 127.xx.yy.zz are reserved for loopback testing. Packets sent to that address are not put out onto the wire; they are processed locally and ...
Tim's user avatar
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1 vote
1 answer
854 views

Is it possible to zero the free space on a LUKS volume?

I want to have a LUKS volume as a loopback device pointing at a sparse file. Lets say I put a 20gb file on it, then later I delete it. How can I zero that area on the device itself so I can fallocate -...
Daffy's user avatar
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0 votes
1 answer
1k views

Is it possible to boot a grub-mkstandalone created img file from cfg?

So I have a fully functional .img file created using grub-mkstandalone. I put this on a CD and it boots fine, the ISO loads great in a VM, etc... Now, what I want to do is link an existing grub.cfg ...
asp's user avatar
  • 101
-1 votes
1 answer
89 views

default network on surface pro 4 is loopback

please look at this amin@amin-Surface-Pro-4 ~ $ ssh 192.168.1.10 -p 1366 ssh: connect to host 192.168.1.10 port 1366: No route to host amin@amin-Surface-Pro-4 ~ $ ifconfig lo Link encap:Local ...
Amin Bakhtiari Far's user avatar