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.
Questions tagged [arp]
421 questions
7
votes
6 answers
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 have a two node exchange 2007 cluster running on two…
lazerpld
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votes
1 answer
Why ARP request is unicast?
I have a wireshark capture that indicating a unicast ARP request from source to destination.
As per my understanding ARP requests (including gratutious ARP) use broadcast.
In what case the unicast ARP request is used ?
Lunar Mushrooms
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7
votes
2 answers
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 side. This gives me 2GB of bandwidth and also…
Ruisu
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6
votes
1 answer
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 explanation, I can only find recommended values…
Jak
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6
votes
1 answer
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) notifies us that it can no longer ping the…
Peter Grace
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6
votes
1 answer
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 Bcast:10.1.1.255 Mask:255.255.255.0
eth1.103 Link…
Andy Coates
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5
votes
2 answers
"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 192.168.201.128 port 22: No route to host
When I try to ping…
user2449761
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5
votes
1 answer
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 connections during a power cycling of the target…
Adam
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5
votes
4 answers
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 dev veth4 set up
$ ip link dev veth5 set up
Let's…
nshy
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5
votes
1 answer
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 and make sense of the data. (The machine I am…
Trinitrotoluene
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5
votes
2 answers
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 crashed. It wasn't responding to the network or the…
Leopd
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5
votes
1 answer
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?
Sandra
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5
votes
3 answers
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: 8.8.8.1 (MAC: 00:21:9b:aa:aa:aa)
Example Server:…
Kyle Brandt
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5
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2 answers
5
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1 answer
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)
^
…
Gang YIN
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