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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How to get a list of all IP addresses (and ideally device names) on a LAN?
Our network gave an error that there was an IP address conflict and I'd like to find what all the device IP addresses are. (I've also had need of that before). (update/clarification:I'm looking for a ...
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Windows 2008 ignores Gratuitous ARP requests
We recently saw an issue after a fail over of our router where our Windows 2008 Boxes didn't start talking to the primary router after fail-back.
When we did some digging they still had the ARP ...
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Is there any way to ARP ping on Windows?
On Linux and other systems, there is an utility called arping which can be used to send ARP requests ("pings") and show the answers, much like the "ping" utility but using ARP instead of ICMP.
Is ...
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How to broadcast ARP update to all neighbors in Linux?
Some clients in the subnet has cached the IP with old MAC address, I want them to update the new value by doing a ARP broadcast, is it possible in Linux?
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ARP broadcast flooding network and high cpu usage
Hoping someone here might have some insight to the issue we are facing. Currently we have Cisco TAC looking at the case but they are struggling to find the root cause.
Although the title mentions ARP ...
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Ubuntu Linux - multiple NICs, same LAN... ARP responses always go out a single NIC
We've got AT&T U-Verse internet service, which has an extremely boneheaded DSL gateway.
We have 5 IPs (netmask 248), but the gateway is incapable of doing anything other than a single IP -> ...
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ARP replies contain wrong MAC address
I've got a robot running linux with wired and wireless adapters. When I boot up, it connects to the wireless fine. When I assign an IP to the wired (either statically or with DHCP), it looks like it ...
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Default arp cache timeout
I didn't found how check and change the default arp cache timeout on Linux.
I using debian with kernel 3.x (but I supposed it same with older kernels)
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What happens when ARP Request comes from a different subnet?
What will happen when an ARP Request packet is sent from router1 to router2 in the following two cases? Will an ARP Reply be generated or the ARP Request packet be dropped?
[router1]Intf1(20.0.0.1/...
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Strange: why does linux respond to ping with ARP request after last ping reply?
I (and a colleague) have just noticed, and tested, that when a Linux machine is pinged, after the last ping it initiates a unicast ARP request to the machine that initiated the ICMP ping. When pinging ...
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Machine always responds to 192.168.1.2 IP address, which is not set on the machine
UPDATE BELOW:
UPDATE 2 BELOW: FINAL Solution
I have a brand new HP EliteBook notebook 8560p running Windows 7 64bit. I plug it into a small Dlink di-604 router, it is currently configured with DHCP ...
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arp-requests cannot be seen by specific nodes
I create an open ad-hoc wlan by using iwconfig (I have the same issue with wpa_supplicant as well). there are 4 nodes on the network as seen on the figure below. The nodes run ubuntu 12.04 and debian ...
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How to find the process which causes the arp request?
When i run tcpdump in the gateway, i get a lot of arp requests originating from the gateway itself. I wonder know why this happens. How can i find the process that causes these arp requests?
$ ...
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Wireshark running on a server seeing lots of `ARP who has` with different tells
We're seeing some suspicious network activity, and when I was trying to see if it was one particular server of ours I ran a Wireshark trace. I noted a lot of ARP packets asking who has x.x.x.x, but ...
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When do STALE arp entries become FAILED when never used?
root@openwrt:~# ip -s -s -4 neigh show dev lan
10.64.42.121 lladdr b8:20:00:00:00:00 used 6387/6341/6313 probes 1 STALE
10.64.42.157 lladdr b8:20:00:00:00:00 used 24/813/19 probes 1 STALE
10.64.42.12 ...
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arp --delete is not deleting an entry; merely marks entry as "incomplete"
$ sudo arp -avn
? (10.10.7.30) at 00:cc:cc:bb:dd:86 [ether] on eth0
...
$ sudo arp --delete 10.10.7.30
$ sudo arp -avn
? (10.10.7.30) at <incomplete> [ether] on eth0
After --delete I expected ...
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Why does Linux answer to ARP on incorrect interfaces?
I have the following Linux networking setup: there is an eth10 network interface with the assigned address 10.11.0.1/24. Then there is a tap0 network interface with assigned dummy address 0.0.0.1/32 (...
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Keepalived send gratuitous ARP periodically
Is there a way for a keepalived to send gratuitous ARP periodically?
We had following situation:
switch failure (VLAN setup)
keepalived failovered to backup instance
backup instance sent gratuitous ...
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Neighbour table overflow on Linux hosts related to bridging and ipv6
Note: I already have a workaround for this problem (as described below) so this is only a "want-to-know" question.
I have a productive setup with around 50 hosts including blades running xen 4 and ...
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Why my laptop sends ARP request to itself?
I have just started to learn about protocols. While studying the packets in wireshark, I came across a ARP request sent by my machine to my own IP. Here is the details of the packet :
No. Time ...
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linux routing bug?
I have been struggling with this not easily reproducible issue since a while. I am using linux kernel v3.1.0, and sometimes routing to a few IP addresses does not work.
What seems to happen is that ...
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Network throughput issue (ARP-related)
The small college where I work is having some very strange network issues. I'm looking for any advice or ideas here. We were fine over the summer, but the trouble began few days after students ...
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ARP reply vanishes from br0 to tap0 using OpenVPN in bridging mode
I have setup a linux box (on an esxi5) which acts as an OpenVPN server. the server is configured to use bridging for the clients, which essentially works, with one exception.
If the client pings some ...
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Dynamic ARP Entries turning into Static ARP entries
I recently acquired a client that has a strange ARP caching issue on one of thier servers.
I have a server that will eventually start turning it's dynamic ARP entries into static ARP entries. This ...
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Is it possible to match an internal IP address to a switch port?
I'm trying to find a computer that has a certain IP address on our internal network. I have identified the computer name from DNS, but in this case it does not help me.
Just wondering if I can ...
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ARP/Mac address table
What is the difference between a mac address table and an arp table? Is it correct to say only one arp cache is kept for each switch which self learns to forward information to another host, and every ...
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Why ARP request is unicast?
I have a Wireshark capture that indicates a unicast ARP request from source to destination.
As per my understanding, ARP requests (including gratuitous ARP) use broadcast.
In what cases are unicast ...
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Is it possible to use proxy-arp back to the same interface?
I have a WiFi Access Point connected to a Linux Router. The Router is itself connected to the Internet. For multiple reasons (mostly to control security and quality of service), I want to force all ...
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How to query the age of an ARP-cache entry in Linux
How can I query the local ARP-cache on my Linux-machine to see when a specific ARP-entry was learned and/or updated the last time?
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Cluster failover and strange gratuitous arp behavior
I am experiencing a strange Windows 2008R2 cluster related issue that is bothering me. I feel that I have come close as to what the issue is, but still don't fully understand what is happening.
I ...
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Cannot ping B from A until B pings A
I have a server cluster all connected on a local network(all physical machines, not virtual). When trying to ping from Server A to B, I get a Desitination Host Unreachable. I can ping from B to A no ...
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How do I poll the ARP table with an SNMP OID?
When you need to poll the ARP table of a device, conventional wisdom is to use ipNetToMediaPhysAddress or atPhysAddress; however, both of these OIDs are deprecated according to Cisco's documentation.
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NIC Teaming with Broadcom on HyperV 2008 R2
I have a HyperV cluster made up of 3 hosts. Each host is connected to both of my Nexus 5548 switches running in an etherchannel. LACP on the switch and NIC teaming using Broadcom 802.3ad on the server ...
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Ubuntu Linux - two interfaces, same subnet, different vlan - MAC/ARP issues
I'm attempting to setup a server that needs to have interfaces on the same IP subnet, but different VLANs:
eth1.102 Link encap:Ethernet HWaddr 00:50:56:b1:00:0f
inet addr:10.1.1.6 ...
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Linux arp cache timeout values
I'm trying to configure sane values for the Linux kernel arp cache timeout, but I can't find a detailed explanation as to how they work anywhere. Even the kernel.org documentation doesn't give a good ...
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Random and Selective ARP blindness in VMWare ESXi 4.1
We have multiple VMWare ESX servers spread out amongst our company, doing various tasks. One particular ESXi host is exhibiting very peculiar behavior. We detect it when our monitoring system (Orion)...
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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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Persistent static ARP entries on Windows, is it possible?
I am currently running coLinux configured in "ndis-bridged" networking mode, on a machine whose wireless networking card or driver seems incapable or unwilling to accept non-broadcast layer 2 traffic, ...
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Which NIC have the IP address?
If I have two NICs where I know the MAC addresses.
Without logging into the server, how do I figure out which have the IP address 10.10.10.10?
Can arp somehow be used for this?
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network level of veth doesn't respond to arp
I decided to play with veth : create a veth pair and
send a ping from one end to another.
$ ip link add type veth
$ ip addr add 192.168.99.1 dev veth4
$ ip addr add 192.168.99.2 dev veth5
$ ip link ...
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Windows 2008 R2 Servers Sending Arp Requests for IPs outside Subnet
By running a packet capture on my my routers I see some of my servers sending ARP requests for IPs that exist outside of its network.
For example if my network is:
Network: 8.8.8.0/24
Gateway: 8....
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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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Sender Information Not Cached on the Receiver During an ARP Request
I'm currently trying to get my head around more advanced networking concepts. The way I am doing this is by going on one of the servers I look after as a sysadmin and running network captures to see ...
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Set up bridged vxlan network in linux
I'm trying out vxlan with linux, and this problem has kept me stuck for days.
Simple Vxlan works fine
Simple vxlan with muticast works for cross-host communication, this simply create a vxlan vtep ...
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Ubuntu 12 crashed and took down network
We recently set up a new Ubuntu 12.04LTS server on our network. It's not fully configured so it's not doing much beyond sshd and a default apache2 install. But this evening it appears to have ...
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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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How to find all hostnames (even laptops that aren't currently on the network) on a network?
I manage a network that has a lot of laptops. The users that use the laptops are frequently traveling. When someone gets a new computer I run into a problem determining what the hostname should be. ...
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ARP packets never routed?
is it true ARP only works in single broadcast domain and arp packets are not routed frm 1 network to another ?
can any one give me any example or any source of info for this
hoping for positive ...
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What happens if I ask 127.0.0.1 via arp broadcasting?
Will all the computers on the network will answer me?