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Questions tagged [icmp]

ICMP stands for Internet Control Message Protocol. It is primarily used by the operating systems of networked computers to send error messages indicating service status.

ICMP is not normally used by end-users or to send messages. It's main use is in diagnostics and checking that the network is functioning correctly.

ICMP is just one communications protocol on the web. Others include:

  • Transmission Control Protocol (TCP)
  • User Datagram Protocol (UDP)
  • Hypertext Transfer Protocol (HTTP)
  • Post Office Protocol (POP3)
  • File Transfer Protocol (FTP)
  • Internet Message Access Protocol (IMAP)

ICMP on Wikipedia

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Sending ARP requests with SmokePing

I have been using SmokePing to monitor my local network for some time now and I'm happy with its graphs and email alerts. I use the fping probe and it works as expected. I found however that, every now and then, some of my hosts won't respond to ARP…
ccrisan
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Block Ping from server using iptables based on packet count

I am trying to block icmp pings from a server if the packet count is greater than 2 per second (packet count reduced for testing). I tried these 2 rules separately but they don't seem to help: iptables -A INPUT -p icmp --icmp-type echo-request -m…
Aditya Pednekar
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Random connection resets between browser and Linux server - MTU wrong or ICMP not getting through?

I've been seeing random ERR_CONNECTION_RESET errors in my browser (Chrome, Firefox or Edge running on different machines, Windows 10 1709) when I try to edit web pages on a remote Linux server running Ubuntu 16.04 LAMP. It's very hard to pinpoint…
Phil McKerracher
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how to push fping.exe (or other ping for windows) to terminate on first reply?

Want to ping specific host with arbitrary number of ICMP requests, but also want to ping program terminate on first reply (speed-up script). Built-in windows ping and few other I tested have not such feature. Anyone known windows ping program with…
user2956477
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Detect faulty physical links with ping

I have a question regarding detecting a physical link problem with ping. If we have a fiber or cable which has a problem and generate some CRC errors on the frame (visible with switch or router interface statistics), it's possible all ping tests…
bdes31
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firewalld - how to block ping ICMP packets?

I can't seem to block ping requests to my server. I also followed the following post: Block ICMP timestamp & timestamp reply with firewalld # firewall-cmd --zone=public --list-all public target: default icmp-block-inversion: no interfaces: …
Ben
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ICMP/Internet checksum if packet entirely constists of zeros

We are currently investigating a strange behavior of different devices: if we send "empty" ICMP packets (that is, ICMP-SEQ and ICMP-ID are 0x0000 and no ICMP payload), for example using nping --icmp --icmp-seq=0 --icmp-id=0 8.8.8.8 then different…
Adrian W.
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Linux VPN router

I have a Linux machine which is set to automatically connect a VPN tunnel into a corporate network. This machine is set to NAT traffic from the local network destined to 194.1.0.0/16** and 10.0.0.0/8 through the tunnel to machines with the corporate…
Ceisc
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Get remote system time from ICMP timestamp

I read from an article that ICMP Timestamp can be used to determine system time so I tried hping3 192.168.1.x --icmp --icmp-ts -V. The output shows len=46 ip=192.168.1.x ttl=xx id=xxxx tos=0 iplen=40 icmp_seq=x rtt=x.xms ICMP timestamp:…
akgren_soar
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ICMP echos and replies arrive, but no ping (kvm hosts and guests)

This are the steps I took building my setup: I have 2 computers (both x86 running Ubuntu 14.04 LTS). I install 2 Virtual Machines (VMs) - one on each machine. Both VMs are Ubuntu Server 14.04 LTS. On one x86 I run one VM using kvm. On the other x86…
orangesomethingorange
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2 Node Linux Cluster - Architecture Validation

so I have a 2 node galera cluster on single 192.168.10.0/24 IP subnet as on this layout: My problem is not about Galera but connectivity. Node1 is unable to reach Node2 via ICMP hence my Galera Cluster isn't working. A. No FW was activated but I…
Nantes
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Accept ICMP packets (ping) with specific length - Iptable rules

I am going to filter Ping request to my server, and only accepts ping request with length 920. ping -l 920 serrveraddress I am using the following two command in iptables iptables -A INPUT -p icmp -m length --length 1:920 -j ACCEPT iptables -A…
rahram
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Using net.ipv4.ip_forward=0 for LXC containers causes DUP! ICMP packets on VMs

I run LXC Linux containers and so I have net.ipv4.ip_forward=1 set on the host so that I can ping internet (google.com) from inside the LXC container. However, when I run VirtualBox VMs in the same environment and bridge to the wlan wireless…
gstanden
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What IPv4 endpoint should I mention?

I am trying to create regular tunnel on https://tunnelbroker.net. Public IP address of our institute is 14.139.196.2. On using this address as IPv4 endpoint address the message "IP is not ICMP pingable. Please make sure ICMP is not blocked. If you…
Shridhar R Kulkarni
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Server with slow ping response

Two boxes with identical loads serving the same sites tend to slow down and stop responding to ping. The slow (or intermittent) ping causes our load balancer to think the servers are offline and disable them. There is a third server with identical…
Joel
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