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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

226 questions
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VLAN Inner Talking

I kinda forgot about CISCO in general, it had been quite a while since I last touched packet tracer. Now I'm on the PRE-deployment phase of a network at work. Long story short. -I made 2 VLAN on CISCO Router and Switch, trunking, encapsulation, all…
Daniel Cruz
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WCF Discovery on Windows Server 2019 getting ICMP Typ 3 Code 3

The problem: I've installed Windows Server 2019 and I am trying to discover my WCF services running on a Windows Server 2012R2. But that's not working and in Wireshark I see a ICMP Destination unreachable (Port unreachable). My current…
squadwuschel
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Why have AWS decided to block ICMP by default on new EC2 machines?

From Why can't I ping my freshly set up amazon web service EC2 instance? it seems that the architects from Amazon's AWS have chosen to block ICMP by default. Is there some official source stating their reasoning for that? I assume it is because of…
sashoalm
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Stop Ubiquiti ICMP restrictions (two concurrent pings at once from same host for traceroute)

How do I change the Ubiquiti Security Gateway's default icmp restrictions from inside the LAN? It seems that my Ubiquiti Security Gateway's default settings will drop icmp packets if I'm doing more than one traceroute at a time, but I can't find any…
Michael Altfield
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icmp_echo_ignore_broadcasts not working for broadcast other than 255

In an embedded system using linux 5.3.18 it is required to ignore ICMP broadcasts. This device IP set to 192.168.0.34/25, so the broadcast will be 192.168.0.127. The flag controlling this behaviour icmp_echo_ignore_broadcasts is correclty set to…
GurstTavo
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Does NAT spoof TCP or UDP port in ICMP payload?

When I send a tcp or udp packet from a network under symmetric nat I expect the port to be different from the one chosen by my computer and so it is. But when I send a udp packet with a low ttl, but that still manages to get out of the ISP network,…
J. Doe
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NBNS Query = ICMP Destination Unreachable

I am having some difficulties when I am trying to get the NetBIOS Name of a machine by it's IP Address with the command (On Windows) nbtstat -A 192.168.1.1, In this example I am trying to get the name of the Router. My problem is that it doesn't…
Dan
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measure the latency/delay with ICMP (ping)

How to measure latency (not rtt) using ICMP (ping) on linux ? The Internet Control Message Protocol (ICMP) is a supporting protocol in the Internet protocol suite.
USER
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nmap - get detailed output for requests?

Update 2: pf already defaults to drop. What causes nmap to notice the server? What does 'received reset' mean? Update 1: Maybe I misinterpreted my findings. When run with -v2, nmap tells me that "Host is up, received reset ttl 52". Does this mean…
loopend
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IPSec tunnel causes huge packets lost when pinging gateway and other machines

My Ubuntu machine is 10.0.0.15, my Windows machine is 10.0.0.10. My gateway, that routes the Internet traffic to the LAN is 10.0.0.1. When I ping the gateway from my Windows machine everything is fine - I get every single packet back. Same holds…
Michal B.
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Disable ICMP reply on CentOS 7 firewall, except some IP blocks

I have a Centos 7 machine with FirewallD, and net.ipv4.conf.icmp_echo_ignore_all is set to 0. I'm seeking for some firewall configs to disable ping replies to external IP addresses, but allow some IP blocks (like 192.168.1.0/24, 10.0.0.0/8 etc.) to…
Mohammad Reza Danesh
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Block ICMP echo responses using the Windows Firewall

I'd like to block ICMP Echo Reply messages from leaving a Windows 10 computer, but still have Echo Requests come in. I created an Outbound rule, but couldn't see which option to choose for replies. Any suggestions?
Fidel
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Stop Windows 10 from sending ICMP Echo Replies

Is there a setting (in the registry perhaps) which disables Windows 10 from sending back ICMP Echo Replies? (Without just blocking them at the firewall)
Fidel
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understanding a psad error for src 0000:0000:0000:0000:0000:0000:0000:0000

My server is generating this psad error. I am not sure what it means? I think it is saying an IPv6 ping request was blocked but am not sure. And if it is a ping request, is it from the server to another device? I don't recall anything on my network…
IMTheNachoMan
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ICMP traffic limit on Google Cloud Plataform

A few weeks ago we realized that there are losses of ICMP packets sent/received between the networks of the telecommunications operator Telefonica / Vivo from Brazil and the IP addresses of Google in the United States (US Central). We have a server…
Consultoria Ti
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