Questions tagged [arp]
Questions pertaining to ARP (Address Resolution Protocol) a communication protocol used for discovering the link layer address, such as a MAC address, associated with a given internet layer address, typically an IPv4 address.
131
questions
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1
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39
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Setting up network manually, no dhcp, IPV4 only
I’m trying to configure ip (static, so without dhcp), there are some problems that I can't resolve by my self, because I do not understand it in a whole. Sorry if it is already answered, but as I said,...
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0
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61
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Enable ARP Announcement on Linux built with yocto
When connecting my Linux computer (Ubuntu 22.04, Kernel 5.15) to the network I see an ARP Announcement according to the Wireshark print screen below.
For an embedded device I build my Linux using ...
- 111
2
votes
1
answer
80
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arptables not working with nmap
I'm trying to implement a way to prevent network scans from my notebook. One of the things I want is to allow arp request to specific hosts, like my gateway.
I added some rules using arptables and ...
- 253
0
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1
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563
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ARP table shows incomplete entry and connectivity lost
I have Linux device running 4.14.7 kernel. My device-A is directly connected to third-party device(Device-B) over 1Gig port. A UDHCPD server runs on dev-A which always assigns single IP address as per ...
- 111
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1
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238
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What's the differnce between "Connection timed out" v/s "No route to host" for ncat command?
I tried to use ncat command to 2 diff unknown IPs from a CENTOS 7 (linux) terminal.
[abc@localhost ~]$ ncat -zv 10.11.78.5 22
Ncat: Version 7.50 ( https://nmap.org/ncat )
Ncat: No route to host.
[abc@...
- 101
0
votes
1
answer
79
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How do I get all MAC addresses of all devices on my LAN that have an IP address (equivalent of doas nmap -sn but for IPv6)?
#!/usr/bin/bash
echo "Give me your private IP and its mask";read given
if [[ "$given" =~ ^([0-9]{1,3}\.){3}[0-9]{1,3}/{0,1}[0-9]{1,3} ]]; then
echo "version 4"
...
- 785
0
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1
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206
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Linux and KVM Qemu VM - "Couldn't ARP for host" despite that host and VM are both bridged and in the same subnet
I am using KVM Qemu in Kali linux host, and trying to practice ARP spoofing. In the Kali linux (which is connected to wired ethernet network), I have set up the following configuration (from tutorials ...
- 629
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0
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53
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Linux Kernel SKB with empty ARP bytes set to zero
I am registering a netdevice notifier in kernel using:
netdev_rx_handler_register(dev, my_handler, data)
Upon receiving network SKBs I check them, and if ethertype is set to ETH_P_ARP I print skb->...
0
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0
answers
150
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nftables - Setting destination MAC still sending ARP requests
I'm trying to run DHCP servers behind a private Docker bridge.
I'm at a point where I can reroute the DHCPDISCOVER broadcast packets to the DHCP server behind the Docker bridge and have the DHCP ...
0
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1
answer
669
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Can't see connected devices ip with "iw dev wlan0 station dump" on raspberry
I have successfully turned my Raspberry Pi into a WiFi access point, but I'm having trouble getting notifications when a new device connects or disconnects from it. Specifically, I would like to ...
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3
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1
answer
93
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What are ARP hardware type 37, opcode 21 and protocol type 0x90bd?
I am currently testing netfilter / nftables / nft. As a starting point, I have made a ruleset that drops nearly everything in and out, and have written the rules so that every dropped packet is logged....
- 3,510
1
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0
answers
96
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ARP request received by one end of ip-link peer and not the other
I have created a network namespace reflector for the interface v-ref.
It is peered to the interface v-test in the default namespace:
sudo ip netns add reflector
sudo ip link add v-test type veth peer ...
- 911
0
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0
answers
1k
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Add static ARP entries on boot [systemd]
I wanted to add a number of static ARP entries that will persist across system reboots. For that I tried using a systemd service which would simply populate the ARP table via the /etc/ethers file:
[...
- 146
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0
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81
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How to add a static route to a router that I do not control?
I am working on a program to control a VPN router running on a Linux SBC. In order to have traffic for the VPN network come back, I need to add a static route to the network's gateway... I don't want ...
- 143
1
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1
answer
770
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Find duplicate IPs for different MACs
Using arp-scan to get a list of returned duplicate IP address. However, arp-scan will list duplicate IP with the same MAC address. I get a sorted output of asx.txt (shortened for brevity)
arp-scan 172....
user552826
1
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1
answer
1k
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How do I set a static MAC address for the default gateway on startup?
I need to set the default gateway's MAC address statically.
I used the command:
arp -s <ip> <mac>
That works, but on reboot the entry is back to being dynamic.
I have tried:
Writing the ...
- 13
0
votes
1
answer
907
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arp -a returns only one device on Kali Linux?
I'm running a Kali Linux live USB. I recently was unable to connect to my Wi-Fi network, but I found a Wi-Fi adapter that let me connect to my network and use the internet without experiencing any ...
0
votes
1
answer
685
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Virtualbox NAT network not showing in Linux
I am currently Running a Bare Metal Kali with Virtualbox installed on it to the run Kioptrix Level 1.
I created a NAT network in preferences with the default recommendations.
This did resolve an ...
- 5
1
vote
0
answers
310
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ARP Entry OPENWRT Not Permanent
I am a bit of a networking noob right now. I am currently trying to get WOL(WOW) working using ARP Entries. Wake on Lan will always work with the configuration i am using right now, sending a magic ...
3
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0
answers
154
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Parallel SSH to 500 docker containers stalls: ksoftirqd to blame?
Answering
How to SSH to over 2000 nodes? I discovered the following:
Running 500 parallel ssh to 500 servers is no problem if either:
the servers are not on the same LAN (i.e. they are routed through ...
- 36k
2
votes
2
answers
4k
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Couldn't arp for host, Kali Linux
I am currently learning the basics of cybersecurity and I am trying to follow the following tutorial on ARP spoofing. I am using kali linux on a VirtualBox VM on my Windows pc to redirect my windows ...
- 29
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0
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965
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How does arp works in IPV6?
In my project, I have a scenario of replace node with IPv6 environment
When I assign one IPv6 address to node1 lets say xyz IP.
By some reason if node1 goes offline, I will need to bring all services ...
- 203
1
vote
0
answers
6k
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Why does an IPv6 neighbour router status become STALE? How can I avoid it?
I have a VM on a host with bridged networking (hence, with its own MAC address). Both host and VM run CentOS. Their network is managed by simple /etc/sysconfig/network-scripts/ifcfg-enpXsY files. ...
- 8,984
0
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1
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88
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gateway sends packets (L3) without data link layer (L2) connection
pretty straightforward question:
#tcpdump -i wlp2s0
[..]
16:33:37.328154 IP 185.29.43.134.https > achille.43692: Flags [FP.], seq 2980347197:2980347221, ack 988779763, win 63, options [nop,nop,TS ...
- 203
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1
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200
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Delete illegal router from network
I have a default gateway with IP address 192.168.1.1 and MAC address 5c:77:76:6e:0d:7b. It is my only wi fi modem router from which I receive internet.
But in input nftables logs I saw another one ...
- 94
2
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1
answer
3k
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How to filter ARP-Requests with Nftables using a Raspberry Pi as AP (using hostapd)
I´m trying to filter ARP-requests coming from certain IP-addresses in my network.
I tried :
table arp filter {
chain input {
type filter hook input priority 0; policy drop;
...
3
votes
1
answer
2k
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nftables Error: syntax error, unexpected saddr
I wanted to add the rule arp saddr ip 192.168.2.1 counter accept to my Nftables firewall. When reading the config-file with sudo nft -f /etc/nftables2.conf, I get the error-message
/etc/nftables2.conf:...
1
vote
1
answer
202
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How does arp_process() replies to the right device?
Looking at Kernel source code I see that when processing ARP request the net_device is retrieved right from the skb, and then seems like the reply is sent to that device (arp.c#L679):
static int ...
0
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0
answers
1k
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how to verify that Gratuitous ARP disabled in a Linux server?
Problem:
I need to verify if Gratuitous ARP is disabled on a Linux server in the configuration files.
0
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0
answers
339
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Arp Reply With Wrong IP - Ubuntu 20.04
This system is Ubuntu 20.04. It has a disabled wireless interface. It uses an onboard Ethernet port. I have a machine that is IP'd 10.0.0.142. It replies to pings on the local network at 10.0.0....
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1
answer
507
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Clients cannot connect to each other on WLAN. No reply on ARP requests
I have install a WLAN with an access point which connects the clients to the internet.
At first all seemed to work correctly until I noticed that the clients
can not communicate with each other.
Here ...
- 221
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votes
0
answers
43
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How to know on which LAN a machine is connected?
I have two LANs (192.168.1.0/24 and 192.168.2.0/24) linked by VPN.
I have one machine (RPI3b+) that I can be connected on the first or the second LAN (I move it).
How can I know where is the machine ...
- 5
1
vote
0
answers
40
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Identify all (arp) devices on network regardless of ip
I have a miss-configured device on the network where I don't know its IP-address.
However since I do know all other devices I want to lookup its IP by using arp. Consider the IP might be on an ...
0
votes
1
answer
3k
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How set MAC address filtering on linux?
I need to block any incoming connection from a MAC address different from a specific one (which is static and well known).
This MAC address should generate only non-IP connection: this is the reason ...
- 51
18
votes
7
answers
3k
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Find the IP address of a newly-booted Raspberry Pi
I've attached a Raspberry Pi running Ubuntu to my home network with a cable. It is booted up and connected to the network. The Pi has no keyboard, mouse, or monitor. If I know the IP address that was ...
- 637
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1
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119
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Why is the server accepting connections after disabling the network interface?
I've googled around and executed other commands (I had left here only the ones that I think are more useful). Most searches pointed me to explanations about how to shut down/up interfaces and no hints ...
- 143
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0
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243
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Machine replies to "arp_requests" for internal addresses even though "net.ipv4.conf.<intf>.arp_ignore" is configured to disable this
I current have a node with an interface connected to the internet (through a VLAN). I will refer to these as eth0 and eth0.100, with the latter being the VLAN interface in the machine.
I preemptively ...
- 11
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1
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346
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set the router's static mac address via isc-dhcp-server
Is it possible to set an ip with its relative mac address so that the clients (during the DHCP request) in addition to receiving the various data, will also directly receive the mac address of the ...
user377583
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2
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987
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arp doesn't run in script when run through crontab
I have a specific script that gets the IP address of a particular MAC. For this it uses arp, and it works correctly. The problem comes when I Program a crontab to run that script; it works fine and ...
- 1,223
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1
answer
9k
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forwarding ARP reply on bridge device
This is my network:
[laptop A]~~~~[ddwrt1]~~~~[ddwrt2]----[desktop B]
|
+--[desktop C]
The ddwrt2 is a wifi router running in client bridge mode connecting to another ...
- 131
1
vote
1
answer
692
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ARP table does not populate if computer has two IPs on same inteface
I have three devices connected to a simple switch. All of the three devices have two IP addresses: one static (172) and one from the DHCP server (192).
Computer A: 172.16.0.1, 192.168.0.1
Computer B: ...
- 175
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0
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85
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ARP Ping to one linux machine throwing No address associated with name
We are trying to use ARP (arping) to reach one linux machine, it throws following error:
exec failed: 1: \S
Kernel \r on an \m
!!!WARNING!!!
###########################...
2
votes
0
answers
495
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arptables-nft persistence
Introduction
This is on Debian Buster with kernel 4.19.0-6
I've installed iptables-persistent and netfilter-persistent versions 1.0.11
and added a basic rule to arptables-nft to block all LAN ...
- 41
1
vote
0
answers
487
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gc_thresh kernel config issues
We were having problems with kernel logs in our datacenter:
arp_cache: neighbor table overflow!
It was related to all of our servers having consul on them using gossip protocol and "flooding" the ...
- 111
4
votes
3
answers
2k
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Parse command arp -a for only ip
I need to parse the command arp -a to get only the ip of the device. Right now I have
arp -a | awk '{print $2}' | head -1
However this gives me
(192.168.1.71)
and I must remove the ( ) from ...
- 43
0
votes
1
answer
1k
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Is there a file for ip neigh show
I am looking for the file containing the output of ip neigh show command. I need the file as I can't invoke command and redirect as per requirement. The closest thing I found is the file /proc/net/arp....
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5
votes
1
answer
10k
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Best way to filter/limit ARP packets on embedded Linux
I have an embedded Linux on some network device. Because this device is pretty important I have to make many network tests (I have a separate device for that). These tests include flooding my device ...
- 53
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votes
0
answers
534
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ARP requests sent from wrong interface on Hostapd managed access point
I am trying to setup a wireless access point, managed by Hostapd and with dynamic VLAN support. The VLANs are managed dynamically by a FreeRadius server that I use for 802.X authentication.
I am ...
1
vote
1
answer
719
views
Does `arp-scan` not work well in a wifi created by a hotspot?
When I use a wifi hotspot, sometimes I can't use sudo arp-scan -l to see other devices (except the hotspot), but sometimes I can see another laptop, but I never see another android phone. (The hotspot ...
- 104k
5
votes
2
answers
14k
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How can I find out the hostnames of other computers in the same local network?
In my local wifi, I can find out the IP and MAC of another computer which also runs Lubuntu, and whose hostname is known to me.
$ sudo arp-scan olive
[sudo] password for t:
Interface: ...
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