Server Fault Stack Exchange
Server Fault Stack Exchange

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
4
votes
3 answers

Reasons to turn off/on unreachables messages?

I see on this question (How can I stop Linux from sending ICMP "Destination Unreachable" responses?) that there was a lot of discussion pointing to the fact that you shouldn't turn off ICMP unreachable messages. I am wondering why and when you…
Paul
  • 253
  • 3
  • 8
4
votes
3 answers

Traceroute, ICMP, UDP and TCP

When does traceroute use TCP? Or does it just use UDP, also why does Traceroute use UDP on MacX and ICMP on windows? I thought ICMP just contains a message saying what caused the error of a packet and does not transmit segments like TCP and UDP.
user171131
  • 145
  • 2
  • 4
  • 7
4
votes
1 answer

tcpdump on interface when pinging nonexistent hosts on local network

I've statically configured the IP address of an interface on a server: ip addr add 10.40.0.6/16 broadcast 10.40.255.255 dev eth1 If I try to ping a machine on the network (e.g., 10.40.0.1), it fails with "Destination Host Unreachable". When the…
Lorin Hochstein
  • 5,028
  • 15
  • 56
  • 72
4
votes
6 answers

Scan for connected, powered on computers on a network?

I want to scan for powered on computers on my LAN and gather logs about that. I tried nmap but it didn't work very well (a lot of switched on computers are not getting detected). nmap -sP 192.168.2.0/24 Nmap done: 256 IP addresses (10 hosts up)…
Jorge Suárez de Lis
  • 391
  • 8
  • 22
4
votes
1 answer

ICMP Redirect Theory VS. Application

I'm trying to watch ICMP redirects in a lab using Cisco Packet Tracer (version 5.3.2) and I'm not seeing them, which leads me to believe that either my lab configuration isn't correct or my understanding of ICMP redirects isn't correct or that…
joeqwerty
  • 109,901
  • 6
  • 81
  • 172
4
votes
2 answers

Stop duplicate icmp echo replies when bridging to a dummy interface?

I recently configured a bridge br0 with members as eth0 (real if) and dummy0 (dummy.ko if). When I ping this machine, I receive duplicate replies as: # ping SERVERA PING SERVERA.domain.local (192.168.100.115) 56(84) bytes of data. 64 bytes…
brandeded
  • 1,845
  • 8
  • 32
  • 50
4
votes
3 answers

Is it normal for AD authentication to generate a lot of ICMP traffic?

is it normal for AD authentication between a workstation and AD server to generate a lot of ICMP traffic? I have a network intrusion prevention in place that is constantly detecting huge amount of ICMP / ping traffic from AD to workstation; vice…
JoeST
  • 41
  • 1
  • 2
4
votes
3 answers

Denying ICMP type 3 code 4 traffic - good or bad?

Investigating a slow VPN connection (Cisco ASA IPSec) to a remote office, I noticed on our firewall a lot of access rule matches: Denied ICMP type=3, code=4 from *ip_address* on interface outside I noticed that a traceroute to the remote site…
dunxd
  • 9,632
  • 22
  • 81
  • 118
4
votes
1 answer

What causes duplicate ICMP ECHO responses?

I've never seen this before, neither have a colleague and an ex-colleague, both with a reasonably strong background in smallish ISP operations. What causes so many duplicate ICMP ECHO responses? $ ping -n x.com PING x.com (196.x.y.z) 56(84) bytes of…
ThatGraemeGuy
  • 15,473
  • 12
  • 53
  • 79
4
votes
5 answers

ping https when ICMP is blocked

I working with web servers that ICMP is disabled on them. On the other hand they answer to some https requests. I'm basically looking for http like ping capabilities in order to check if another server can reach that machine, and get some data about…
qballer
  • 153
  • 1
  • 1
  • 9
4
votes
1 answer

Why isn't ICMP routing with iptables nat routing

I'm using iptables on Ubuntu server to route a public IP to a private IP. I want to nat all traffic, including 80, 443 and ICMP. However, it appears that ICMP isn't routing. I have a steady ping going to the public IP and it never stops, even with…
Scott Forsyth
  • 16,449
  • 3
  • 37
  • 56
4
votes
1 answer

How to make Windows honour an ICMP Connection Refused message after a TCP connection attempt

We have a tool which is used to manage a server process remotely over TCP. One of the tools features is to check if the server is running by attempting to connect to the server in a loop for a given period of time. When we used the tool to check…
liwp
  • 161
  • 4
3
votes
1 answer

How to monitor ping packet loss via prometheus exporters?

I'm already trying to use this exporters for simple icmp probes: https://github.com/prometheus/blackbox_exporter It gives only 3 icmp latency metrics https://github.com/czerwonk/atlas_exporter Only metrics for atlass…
Kein
  • 131
  • 3
  • 14
3
votes
1 answer

Forwarding ICMP response to TAP interface

I am trying to do a test where I forward ICMP responses to a TAP interface. I created a TAP interface and assigned it the address 10.0.4.1/24. My linux setup uses the interface enp0s3 as the default option. To forward any ICMP response to the TAP…
Jake
  • 145
  • 8
3
votes
1 answer

How to stop Windows Filtering Platform blocking ICMP packets for legitimate RDP traffic over L2TP tunnel?

RDP via Windows 2008 L2TP to Windows 10 Pro did never work flawless. The first attempt in September 2018 needed the client Cord.app to be replaced with Royal TSX on OS X 10.9.5. The remote Win10 box crashed and was recently re-installed with all…
Pro Backup
  • 984
  • 4
  • 15
  • 35
1 2
3
…
15 16