Questions tagged [arp]

Address Resolution Protocol is a layer 2 networking protocol used for resolving layer 3 addresses (such as IP addresses) into layer 2 addresses (such as Ethernet MACs). It is used by network devices when communicating with devices on the same layer 2 network.

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ARP finds router but PING not successful on Ethernet; wlan works

I have a really weird issue with my home network. Sometimes my ethernet stops working entirely so I cannot connect to the internet. The wlan still works in those cases. My routers internal IP address ...
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can ping but not arping via OpenVPN

I'm working on a remote machine using OpenVPN at a customer's network. The IP addresses there change dynamically and (until they get hostnames to work properly which is not in my hands at this point) ...
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Why is nmap slower than arp-scan?

I am trying to find hosts on my network by doing an ARP scan. I first did this using the "arp-scan" tool (available on most linux distributions): arp-scan 192.168.86.0/24. This printed ...
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Windows Incorrect MAC Address Populating ARP Table

Recently I have been running into issues where incorrect MAC Addresses are populating the arp tables of some Windows VMs running in a Cloud Provider's cloud. For example, if I ping 10.1.2.3, some ...
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What are the symptoms of an IP address conflict?

System administrators must take special precautions when setting up two DHCP servers on the same network. The most common problem caused by competing DHCP servers is an IP address conflict. Windows is ...
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306 views

Strange entries in ARP table

I noticed some strange public IP addresses in the ARP table of my Ubuntu laptop. They also keep reappearing quickly after flushing it. The adresses all resolve to bc.googleusercontent.com and only ...
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Finding static IPs after reboot

I am having troubling pinging IP addresses on the local network after rebooting or clearing the ARP table. I am looking for guidance on fixing this. I have a windows 10 PC which is has a 4 port ...
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38 views

ARP table emptied when TAP interface is added to bridge

I have a problem with ARP table on CentOS. Sometimes, when I create a TAP interface and add it to a bridge, the ARP table is cleared up. E.g. when I execute this command: sudo ip tuntap add dev tap-...
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Same VIP different MAC

I am observing this behavior on a dual-homed server that is sending traffic in active/active mode on its 2 links connected to the same uplink switch. The server is running IPMP so it generates traffic ...
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pcs status command is showing failed resource actions. pcs resource cleanup is also not working, because they keep coming back

I have corosync and pacemaker configured in my environment but on pcs status, I keep seeing failed resources as shown below Failed Resource Actions: * vip03_monitor_10000 on vm01 'not running' (7):...
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How to make Linux kernel send ARP requests down multiple network interfaces with overlapping subnets?

I have a Linux PC with the following physical network interfaces: Primary LAN/Ethernet port used for most traffic. Ethernet (from external device) to USB (into my PC), used to connect to a single ...
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Google Cloud VPC: Is there any restriction on N-S traffic and ARP requests from alias IP?

Platform: Google Cloud VPC Scenario: We are trying to integrate our cloud infra solution within GCP instances using nested virtulization. The solution includes a SDN component which performs both L2 ...
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bonding issue with ethernet interface (raspbian strech)

Since i've bonded (active-backup) eth0 & wlan0 i'm no able to ping a specific device within my LAN. I'm under raspbian stretch. Linux raspberrypi 4.19.66-v7+ #1253 SMP Thu Aug 15 11:49:46 BST 2019 ...
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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 +--------+ +----------+ +-----------+ +---------+ ...
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rsync broken pipe between two servers on different networks

I have two FreeBSD servers, both on different networks, with a firewall in between. I have no control over the firewall. Server 1: IP: 10.1.0.2 GW (firewall): 10.1.0.1 Server2: IP: ...
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How am I receiving ARP brodcasts from a different subnet?

My local IP/subnet is 10.33.19.*/24, and yet I am occasionally receiving broadcasts requesting information from and concerning IPs in the 10.17.*.* range. I was of the impression that ARP requests do ...
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Unexpected ARP Probe and ARP Announcement on Windows 10

In our system, there are three hosts all connected to the same Ethernet switch, which is illustrated below: A (192.168.0.21, WIN10_1809) <-> Switch <-> B (192.168.0.100, Debian Linux 9) ...
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Why is my client still talking to my server when I change client IP to different subnet?

On occasion, I'm using a Verizon Mifi adapter to share an internet connection over my office network (which doesn't have internet). To do this, I have to share the internet connection on the adaptor, ...
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Two devices only one shows name of devices when running arp

I have two ubuntu devices both connected directly to a router. When I run arp on one device I get devicename (123.456.78.9) at 01:23:234 [ether] on eth0 On the other device I get ? (123.456.78.9)...
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Lots of IPs with MAC 00:00:00:00:00:00 . What are the possible causes?

On my enterprise we have some times this ARP output (read on a computer with Linux): $ cat /proc/net/arp 192.168.0.176 0x1 0x0 00:00:00:00:00:00 * eth0 192.168.0.93 ...
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Laptop A is sometimes blocked from pinging laptop B. Pinging in reverse unblocks it

I have had this problem dozens of times, ususally spaced out by days or even weeks. Router R can ping laptop A, laptop B, and the internet (0% packet loss in each case). Laptop A can ping router R ...
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100 views

Proxy-Arp setup with Keepalived

I currently am trying to create a setup with N servers where 1 server is the master for a Virtual IP, and the (N-1) servers act as backups, presumably controlled by keepalived. However, one issue I ...
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How do l manually set an arp table entry to reach an otherwise unreachable host in debian

I'm trying to reach a host on an internal network whose configuration has gotten screwed up, and isn't pulling a DHCP lease as would be expected. I have a host on that network that l'm trying to use ...
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arping not working in docker

I'm currently trying to add a presence feature in my OpenHab installation by detecting presence of our mobile phones. For iPhone an arping is necessary, unfortunately it looks to me like arping won't ...
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133 views

Same IP on two NICs half the traffic is lost

I have a machine connected to a slightly broken scientific instrument and I'm trying to work around the problems. The link is point to point, 2x25G ethernet, no other devices involved. The device ...
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705 views

Is there is any tool/way to find out why packet is getting dropped due to an arp cache full?

My developer hypothesis is packet is getting dropped at arp layer. We increased the default value of neigh.default.gc_thresh3 1024 --> 2048 and now everything looks good. But I want to understand is ...
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125 views

Router ignores ARP response from linux

I have just viewed my local network traffic with Wireshark to solve a connection problem of another device. I noticed that my router constantly asks for my MAC address via ARP, but ignores the answers ...
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256 views

High bandwidth ARP traffic on LAN interfaces

I'm using a PfSense Firewall with a few VLANs since over 4 years and in the last couple of days I've noticed network connectivity issues in two of the VLANs. Using the web interface I'm seeing ...
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Debian / Kerio is ARP storming my ISP after loosing connection to the gateway

The problem: after Kerio Control (Debian) lost connection to the gateway it starts sending ARP like for "who has 8.8.8.8?" in such frequency, that the gateway gets shut down due to packet inspection ...
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618 views

QEMU/KVM/libvirt macvtap VEPA not working - ARP request not forward

Hi I've been struggling to get guest networking working when using a macvtap in VEPA mode between two VMs on a host. I've spent hours (days) googling with no joy. Does this network configuration ...
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Why Nmap doesn't arp-scan find any devices when does?

When I run nmap -sn 192.168.0.0/24 I get the result: Nmap scan report for 192.168.0.1 host is up (0.16s latency). Nmap scan report for 192.168.0.103 host is up (0.19s latency). Nmap scan report for ...
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NIC bonding on Linux in redundant network topology

I want to implement NIC bonding on Linux server in redundant network topology as shown in the network diagram below. Network topology Both interfaces of the Linux server fa0 and fa1 would be in one ...
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1answer
247 views

Why do some unknown hosts show up with nmap option-sL , and not with -sn [and do I need to worry about them]?

Initial Disclosure I am not a network engineer and my expertise in this area is low. Background while using nmap 7.70 with nmap -sL to look for the IP address of a known device on our local ...
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Feasibility of having two independent subnetworks on interconnected switches

I have the following setup, using two standard cheap switches that are interconnected by a long Ethernet cable: |------ SWITCH #1 | [ ] Equipment with public IP 217.x.x.101 (subnet 217.x.x.96/29) | [ ...
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Industrial switches failing to pass broadcast traffic/ARP requests very slow

I'm dealing with some industrial Ethernet switches (Phoenix Contact FL Switch SF 16TX) which are connected to about 5 computers and 5 SLC/5 PLCs. We are having an issue where ARP requests are not ...
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303 views

Behavior of ARP when using VPN bridge

I'm experiencing trouble connecting infrastructure using VPN. i don't have lots of rights with the VM i'm using so it's hard to give you précision, so this topic should be theoretical. There is 3 ...
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Too much ARP 60 Packets and Network is getting very slow

I am seeing too much ARP 60 packets from one IP in wireshark. Our LAN is getting too slow, But the internet is working fine without any issues. But cant access local printers, file share etc Am ...
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735 views

Setting up Linux bridge for all VLANs (tagged) when bridges for same VLANs (untagged) exist

TL;DR: Does anyone know how to get bridges associated with a VLAN (like virbr0.101) and a generic bridge that supports all VLANs (like virbr0) to co-exist? Sorry for the rambling backstory, but I'm ...
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110 views

Manually building an ARP table

I am using a real time operating system called Vxworks 5.5. The address resolution protocol is disabled and now I need to build up an ARP table manually to initiate IP to IP communication. The IP ...
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370 views

Docker Linux network topology using route tables and arp

I'm working with a network of docker containers. C1's routing table is below, it's default gateway 172.17.0.1 is the docker bridge. It's eth1 interface is connected to eth2 in C2 and it routes all ...
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286 views

Windows 2012 R2 Domain Controller making ARP requests outside of subnet?

I have a Windows Server 2012 R2 box acting as a Domain Controller which is on a segregated LAN. It also acts as the DNS server for this LAN. I also have a Sonicwall NSA 2600 firewall which is set as ...
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105 views

Can I use source MAC of Ethernet packet for UDP reply instead of ARP lookup?

I'm working on an embedded platform with very limited resources where I need to build my own Ethernet frames. If I need to answer a UDP request with a UDP reply, is it ever not OK to just send the ...
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450 views

nmbd “Packet send failed” error

I'm desperately trying to get folder sharing over SMB working on my local network. I'm running up-to-date arch linux and connecting over wifi using wicd. I have latest samba installed (4.10.4). While ...
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1answer
342 views

How to fix the network after ARP poisoning attack?

I was running a program called morpheus: https://github.com/r00t-3xp10it/morpheus. It is a github project which allows ARP poisoning attacks, MITM attacks etc. I was running a arp spoofing/phishing ...
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“No route to host” until “ping” or “route”

I have two computers in one WiFi network: A - client B - server Sometimes (once in ten times) after B reboot I am unable to ssh from A to B: $ ssh 192.168.201.128 ssh: connect to host 192.168.201....
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784 views

how to set skb->priority of ARP packets

As the title already specifies, I'm looking for a way to set the linux skb->priority of outgoing ARP packets of a given interface on my linux machine that is used as a router. The skb priority is ...
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258 views

Arping does not work in a script

In my network I have one linux host as a default gateway located at 192.168.150.1. On another host at 192.168.150.4 I have this script to measure time between sending an arp request and receiving it: ...
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137 views

Linux: answer arp instead of the kernel?

Is it possible to answer ARP requests in user mode instead of inside the kernel? I can create a ETH_P_ARP socket but not sure if I can completely replace the kernel strategy at this level.
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896 views

ARP table not updated until response is sent

I'm executing the arp -a command on CentOS 7 in order to translate an IP address to a MAC address (since I can't access the source MAC of the layer 2 frame in Java). I see a lot of cases where the ...
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906 views

VPN Router does not reply to ARP Requests

So i have these three network interfaces setup on a linux box: eth0 is facing the external network (192.168.1.0/24) tun0 is the vpn interface (10.8.8.0/24) eth1 is the local network interface (...

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