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 behavior in Linux

I have a L3 switch. Port 1 and port 2 of the switch are added to VLAN 30 and an IP address (30.0.0.1) is assigned to it. Port1 and port2 are connected to Host1 and Host2 respectively. Host 1 and ...
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Xen networking - dom0 receives ARP requests but no reachability

Both dom0 and domU are Debian 8. Dom0 network configuration is: auto xenbr0 iface xenbr0 inet manual bridge_ports eth1 bridge_stp off bridge_waitport 0 bridge_fd 0 auto xenbr0.4 ...
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178 views

Windows 10 arp cache getting stuck after failed attempts when target machines are offline

After upgrading our development team to Windows 10 from 7, we are experiencing an issue with the ARP cache where a machine has the correct IP-MAC mapping cached, but the type is invalid due to failed ...
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Ping problems with two interfaces, same subnet, direct connections to two separate hosts

I have a configuration of a client machine (Ubuntu 14.04.2 LTS) that directly connects to two server machines. The server machines--while on the same subnet--cannot route to each other. Packets must ...
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384 views

Keepalived failover not working for Static NAT target behind Cisco ASA

I've got a Cisco ASA[0] with a pair of Linux boxes in the DMZ running Keepalived and HAproxy acting as a load-balancing failover pair for another pair of Windows servers, also in the DMZ. I'm ...
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267 views

I am not able to connect to my server from my leased line internet connection

I am having some troubles connecting to my Fedora server from my static IP ISP connection. Usually I can ping that server with no problems. But other times it just gives me timeout responses. When ...
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226 views

Solaris 10 invalid ARP requests from 0.0.0.0? Link up/down every hour or 2

The guys at the data center where I'm hosting a server running Solaris 10 are telling me that my server is making a lot of invalid arp requests. This is an example of a portion of what was sent to me ...
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76 views

ipwatchd detects non-existing conflict?

Ipwatchd is telling me about a conflict that I just do not understand. As far as I can tell, there is no conflict. Am I reading the message wrong? It's a Xen machine with the following network ...
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125 views

Can ARP with IP aliases on Windows be made to behave like on Unix?

On FreeBSD, when I have one interface with two IPs: ifconfig nic0 192.168.0.1 netmask 255.255.255.0 ifconfig nic0 alias 192.168.0.2 netmask 255.255.255.255 If I ping the alias, if the host I'm ...
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Understanding arp request tcpdump

I noticed the below tcp dump when pinging a docker container B on bridge B from a docker container A on bridge A. Container A: 10.0.0.3 / 02:42:0a:00:00:03 Container B: 10.0.0.4 / 02:42:0a:...
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ESX 6 arp fails in back 2 back link

we are having a strange problem with back 2 back connection between an ESX 6 and CentOS 7 machine. Hoping to find a solution on stackoverflow The story is below: - we are using a CentOS 7 directly ...
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65 views

ARP issuse in SUSE Linux

I am dealing with a very strange problem. I have a VM running SLES 11 SP4 in VMware Environment. The machine has two NIC. All of a sudden the second NIC stopped working. It's not even pinging the ...
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30 views

Arp reply on behalf of another devices on Linux

There are devices on a network that don't support ARP (let's name them NARPs) and a device that supports ARP, running Linux (lets' name it LX). LX knows the IP and MAC addresses of NARPs. What is ...
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50 views

Broadcast ARP weirdness

we a running a router on a custom Linux box. Kernel is 3.14.14. What happens is that when you arping the router in broadcast only mode is the router has a verey slow response time: # arping -b -c ...
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324 views

Linux bridge not answering arp packets

I'm trying to setup a test scenario regarding linux bridges for which I need a full virtual IP stack. Basically, I'd like to simulate the network between a VM (or container) and its host, just without ...
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191 views

linux not replying to an arp request

I am running linux 3.14 on a system with 2 interfaces. on the first interface, i can access our local network. on the second interface, arp packets come in but linux doesn't send out reply. is it ...
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375 views

Broadcom NICs, Cisco ASA and ARP request collisions

First of all I am sorry for my english mistakes. Help me please to solve the problem with ARP request collision incidents. I have IBM BladeCenter E chasis with blade servers are installed in this ...
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244 views

Duplicate entries in switch ARP table

A server is showing twice or more on my L2 switch ARP table Same IP address, mac address, and ethernet port. What could be causing this? Thanks
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241 views

ARP Tables on Windows vs Linux

I noticed on Windows Server 2008, Windows Server 2008 R2, and Windows 7 that IP multicast groups joined by a computer are recorded in the ARP table as static addresses automatically. However, the same ...
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2k views

VMWare ESXi 5.0 Networking Issue

I have an issue with 2 new ESXi hosts. OS - ESXi5.0 Custom Dell ISO patched up to Build 1024429 DELL R820 with 1G network 2 ports from integrated MB NIC(Intel) connected to 2 juniper switches, one is ...
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296 views

Keepalived, Junos, and ARP caching

I'm trying to configure an active-passive stunnel setup, with the aid of Keepalived, for a public IP address at our company datacenter. I would like to know if a router or switch reconfiguration is ...
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1k views

arp reply is not processed

My eth0 interface does not process a legitimate arp reply. When I try to ping a host, I see arp request and reply with tcpdump from the host I try to ping from, but ip neigh says that there is a ...
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701 views

Cannot ping any machine on local network (embedded linux device)

I have an embedded linux installation (custom built using buildroot, uClibc and busybox) and I am unable to ping any machine on my local network. My /etc/network/interfaces file is as follows auto lo ...
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363 views

stop arp poisoning on a 5448 powerconnect switch

We have to disable arp poisoning on our dell 5448 switch. Right now it has all our production machines running on it and I'm not a networking guy at all so I don't want to run a command that will ...
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157 views

What is the meaning of the QUEUE in arptables

I use the nfqueue target of iptables in order to get packet to the nfqueue and do some business rules on them. iptables -A INPUT -p tcp -j NFQUEUE --queue-num 0 I need to do the same on arp reply ...
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1k views

Arp request is not resolved

On my machine, I have assigned ip addresses for two interfaces which are connected through a cable. They are connected with 10G ports. When i tried to ping the two addresses, ping was not working. ...
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64 views

Server Core DNS Server in VSphere doesn't respond to ping and needs continuous arp clean

I have a VSphere installation hosting two Windows Server 2008 R2 installations. One of them is a complete install that serves as a DHCP server and that I use for administration. The other install is a ...
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384 views

virtualbox bridged adaptor works only guest->host but not host->guest

I have virtualbox 4.1 on a ubuntu 12.04 host. On my host I have a virtual interface eth0:1 configurend as 10.0.1.1. I have a few virtual machines using bridged adapters, configured in the 10.0.1.0 net ...
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356 views

Windows Server 2003 DC sends Gratuitous ARP requests with wrong IP

Hello and excuse me for my English please. ;-) Two server seems to be involved with this problem. Our DC (domain controller, 2003) an the VMware VC-Server (2008 R2). After capture "some" network ...
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Diagnosing the source of improper ARP requests on WAN side of Linux firewall/router

The kernel log on a Linux firewall/router I administer recently started filling with messages like these: net_ratelimit: 405 callbacks suppressed neighbour: arp_cache: neighbor table overflow! ...
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initial connections refused - connection warm up?

I've got two firewalled VMs connected to the same vLAN but I see RST/ACK responses on initial connection attempts in a while only to succeed on immediate following attempts, like some sort of cache ...
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49 views

“No route to host” when i do a telnet in azure

I have two VM's in azure with different public IP's and whose private IP's are : 10.10.1.9 10.10.1.6 When i do a telnet with following command from the server 10.10.1.6, i get the a error: telnet ...
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Firewall thinks ARP is being spoofed

My firewall log is filling with messages about a possible ARP spoofing attempt on my own LAN: 192.168.111.60 is a Synology RS815RP+ NAS on my LAN. 192.168.111.7 is a Lenovo EMC px4-300r NAS. Both ...
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Frequent unicast ARP requests

Wireshark screen I would like to ask if it's considered to be a normal behavior of a router to issue this many (as shown in the screenshot) "refreshing" arp request? As I do not see, for instance, my ...
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What is the difference between arp_ignore and arp_filter?

What is the exact difference between the arp_ignore flag and the arp_filter flag defined in syctl.conf in Linux? Both seems to serve the same purpose.
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arpwatch to listen only to particular network

I deploy arpwatch is our network and it is working fine. But it is not doing exactly what i need. Here is what i need ... i want it to listen to one particular network ... for example on ethernet 0 it ...
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51 views

ARP cache getting null mac over a bridge

I have an interface eno1 and a bridge br0 $ ifconfig br0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500 inet 192.168.250.53 netmask 255.255.255.0 broadcast 192.168.250.255 ...
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Cisco 2960X & IPDT

I am interested in finding the IP addresses assigned to devices attached to each interface on a Cisco 2960X switch. It seems like IPDT is exactly what I'm looking for. However it seems like the ...
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Ubuntu - Destination Host Unreachable Through Router / ARP Requests

Very strange issues on an Ubuntu server running DNS. Here is the network setup. There are two class C network ranges. Let's say they are: 216.107.249.0/24 216.107.250.0/24 Server is assigned an ...
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http cookie contains datr not working (none packets is returned) wireshark

When I filter in wireshark: http.cookie contains datr none packets is returned, the list in null. What's I going wrong?
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(solved -> bug) forward arp packets as vlan tagged arp packets

How can i forward arp packets as vlan tagged arp packets? e.g. arp packet (no vlan tag) -> eth1 -> eth2.1 -> arp packet (with vlan tag) With the following setup, the outgoing arp packets (on eth2.1) ...
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why iptables SNAT doesn't help to answer ARP on the vlan tagged subnet?

I'm using iptables SNAT to setup a "router" on a linux box, it suppose to do NAT for 2 subnets. one untagged subnet 10.0.10.0/24, the other one is vlan tagged subnet 172.16.0.0/24. both subnet come ...
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132 views

Ping is happening but arp is not resolved

I am seeing one interesting problem. I have setup two devices connected through lan cable over eth3 interface. Now a vlan session has been created on both the interfaces. Device 2: root@10:~ >...
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171 views

ebtables arp filtering with openvpn tap interface

I want to prevent arp traffic not destined for the remote side going through a openvpn tunnel so I filter arp requests going to none of my own IPs. Server Setup: /etc/network/interfaces auto br0 ...
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What causes the Linux neighbour table confirmation counter to be reset

Given three linux hosts on the same broadcast domain, the sender constantly pings an IP bound to receiver1. When moving the IP address from receiver1 to receiver2 it takes a quite long time for the ...
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Wireless devices see ARP replies but not requests, monitor interfaces see both

For the sake of brevity, let's call the wireless interface used for access point (AP) to device communication "wlan0" and the interface used for sniffing in monitor mode "wlan1." In my case, wlan1 is ...
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79 views

MAC address in arp table doesn't match actual MAC, why?

If I connect my laptop directly to the config port of a ubnt airFiber radio I can set a static IP to my laptop and access the default config page to change settings on the radio. When I look at the ...
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266 views

ARP/ICMP in a network environment with overlapping IP address

Currently I have lab network setup to mimic customer's network deployment. (According to the customer, they are using VRF over VLAN so that their customer can have overlapping network connecting to ...
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749 views

VMWare use of Gratuitous ARP REPLY

I have an ESXi cluster that hosts several Windows Server VMs and around 30 Windows workstation VMs. Packet captures show a high number of ARP replies of the form: -sender_ip: VM IP -sender_mac: VM ...
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41 views

SYN-ACK with identical MACs

What could cause a CentOS machine to respond with SYN-ACK packet having both source and destination MACs set to the address of the NIC from which the packet is being sent?