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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

130 questions
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What is the purpose of using a large ping packet?

While analyzing some traffic logs, I noticed a node pinging its gateway with a large ping packet size, ranging from 700 bytes to 1 MB. It's a constant ping from node to gateway and the size per ping is rather high. Does anyone know why this might be…
injector
  • 950
25
votes
2 answers

what is type of ICMP packets? TCP or UDP

The ping packet is a type of ICMP packet. Is there any relation between ICMP with TCP? In other words, can we guarantee their arrival in the network? I want to know if ICMP packets in the network are TCP, UDP, both or none of them?
Mohammad Reza Rezwani
  • 693
25
votes
3 answers

Linux: How to monitor incoming pings

Can I somehow monitor incoming pings on a Linux machine? netcat doesn't seem to support that.
futlib
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15
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1 answer

What is ICMP broadcast good for?

To configure Linux to ignore ICMP broadcasts (to protect from SMURF attacks), I have added the following line to /etc/sysctl.conf: net.ipv4.icmp_echo_ignore_broadcasts = 1 Anyone knows what are the drawbacks of ignoring ICMP broadcasts? In other…
brahima
  • 153
12
votes
3 answers

How ping a server which has ICMP blocked

I'm trying to ping a server which has ICMP blocked with normal ping. It's showing: Request timed out Is there any other method to ping it?
user446633
  • 121
12
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4 answers

What are reasons to disallow ICMP on my server?

An EC2 Instance has ICMP services disabled by default. While it's not totally clear to me why, I think it's because it could be a potential security risk. At the moment I'm enabling Echo Responses only when I'm restarting the server so I can see if…
3k-
  • 223
10
votes
1 answer

how to test ntp servers as real servers that responding without using ping test

we have bash script that configured the chrony.conf script check if ping is ok on ntp1 and ntp2 ( ntp servers ) and then script insert the ntp servers to /etc/chrony.conf ( only if ping success ) example from bash script: ping -c 1 ntp1 if [[ $?…
King David
  • 1,001
8
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How do I forward traffic between Tun device and eth0?

In summary, I would like to have Tun device traffic forwarded back and forth through another network interface that has internet connection. While I can see the traffic going out to internet and coming back, it is not routed back to my Tun…
askldjd
  • 183
7
votes
2 answers

Ping doesn't work when using QEMU user mode networking

I try to use network in guest system. I installed an OS in a virtual machine, but I did not get the network configured. When I try to ping, for instance google.com I get the IP address for the domain, but packets are not transmitted. I tried several…
mcsim
  • 171
7
votes
2 answers

SSH and PWNAT for SSH Connection Between Two Separate NATs

Is it possible to use pwnat and SSH to establish a "peer-to-peer" SSH connection between two machines that are behind two separate firewalls/NATs? If this is possible, what are the steps that would need to be taken to set up this functionality on a…
Kevin Gurney
  • 369
7
votes
7 answers

Can the maximum ping size of 65500 bytes can be increased?

Can I override the default maximum size - 65535 bytes of ICMP ping packets? If - then How?
d3vdpro
  • 286
7
votes
1 answer

ICMP packet with TCP?

For some time now I have found myself interested in packet analyzing and I try to figure out all kinds of stuff that I see in network captures. I hope you guys might want to help me find out this one. In a company network, I see a Fortigate 100E…
Deluccio
  • 73
6
votes
1 answer

Why does the 2nd ARP request wait until the pings are over to show up?

This problem was presented to me by one of my professors because it only happened after switching from 100Mb cards to Gigabit NICs. The second arp request that comes from the computer being pinged (to send a reply back) doesn't get sent until after…
SkyParrillo
  • 61
6
votes
2 answers

Why ICMP is different that TCP and UDP?

what is the difference between Internet Control Messaging Protocol over Transmission Control Protocol and User Datagram Protocol
Bidhan
  • 97
5
votes
1 answer

Is there a way to test alternate IPv4 routes?

i am using Hurricane Electric's Tunnel Broker service to get IPv6 connectivity. TunnelBroker lets you have access to the IPv6 Internet by using a standard IPv6 tunneling protocol. You send IPv6 packets, wrapped inside IPv4 packets, to one of their…
Ian Boyd
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