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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.

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can't ping my own IP address (interface with multiple IP Addresses)

I have a server where one of its interfaces (eth2), has multiple IP addresses: $ ip addr show 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default link/loopback 00:...
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DPM breaking network connectivity to itself

I'm backing up a specific folder in a VM (server 2016) with DPM (SC2016). Both have all the updates installed, latest patch versions. I noticed that after the initial replica, the backups have been ...
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nic: Something Wicked happened! ffff

I'm configuring a GNU/Linux Router with Debian Stretch (9.7) and before rebooting the server, all traffic from one interface to another was going ok, but after that, I received a message like this (...
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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 ...
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How do I do traceroute/tracepath without any admin privileges?

Basically, I need to "trace a packet from my computer to the host" to diagnose a network issue and I do not need any fancy additional functionality. Redirect me to the right place if this is not the ...
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Linux equivalent of “no ICMP Unreachable” and “no ICMP Mask Reply”?

I have a Linux machine that is being used as a router. It has quagga installed and has ip forwarding enabled. It's forming an OSPF adjacency with a 3925 Cisco router. I'm being asked to ensure that ...
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1answer
130 views

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 ...
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What should be the behavior after also dropping outgoing destination-unreachable packets?

On system A I'm using ip6tables and I'm DROPing INPUT packets coming from system B through IPv6. As expected, when system B uses ping6 to system A, it sees destination unreachable. However, when on ...
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Is RTT theoretically the same regardless of ping origination?

Let's say you send a ping from device 1 to device 2. The result would give you the RTT. Theoretically speaking (because many variables are realistically in play), would the RTT be the same by ...
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Layer 3 Device ICMP behavior and impact on tracert

Is it possible to configure a layer 3 device to set the TTL of all ICMP echo request packets to zero and not send out ICMP Time Exceeded message ? If so, wouldn't this make it impossible for tracert ...
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ICMP packet size over 372 are dropped on bond0

i have a target server running on rhel7.4 with kernel 3.10.0-693.11.6.el7 with bond0 and subinterface vlan2001 with MTU 9000 when i ping from a different server which is in a different network with ...
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iptables, filter pkttype broadcast, ARP and ICMP

I found a brief explanation of this filter. https://www.netfilter.org/documentation/HOWTO/netfilter-extensions-HOWTO-3.html 3.10 pkttype patch This patch by Michal Ludvig adds a new match ...
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ICMP maximum delay between echo request and reply sustained by a router NAT

I was trying to slow down network on my server (arch linux vm) with netem sudo tc qdisc add dev eth0 root netem delay 1600ms With 1600ms delay client doesn't receive the echo reply packet though the ...
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How to identify PID of process that is generating lots of ICMP ping requests?

I have a box that is generating lots of outgoing ICMP requests. I am able to see a few happening every second with tcpdump -nni ens192 icmp. However, I don't have anyway of tracing these back to the ...
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Is icmp ping a reliable way to monitor host up/down in EC2?

We use icmp ping to determine host up/down status from icinga2 in our AWS EC2 environment. This works well, but we have had a handful of issues where host will fail ping but its services are still ok. ...
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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 ...
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How long is an (accepted) ICMP redirect observed for, and how can I shorten that time?

If a Linux host receives and accepts an ICMP redirect (accept_redirects=1 on the interface in question), how long is this route being cached for and observed? Can I lower that time? I am asking ...
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164 views

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: ...
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Printer stops pinging after 3 minutes from IPSEC remote side. Continues from local side

I have a very strange issue that I have come across twice now. It is making me go cross-eyed. We have two sites, one runs our server infrastructure and the other hosts end-users. There is an IPSEC ...
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1answer
61 views

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 ...
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334 views

tcpdump host unreachables for specific host

I'm trying to rule out some issues and needing to capture all ICMP messages except echo/echo reply. However the issue I'm struggling to find a way around is I only want these involving a particular ...
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1answer
48 views

Split ping RoundTripTime

Data obtained from ping: is it round trip or one way? shows that the data of a ping measures both directions together. Is there any way to split this information in time-to-destination and time-back?
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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 ...
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drop ICMP, can not remote login server any more

for a security reason, I config iptables to drop ALL icmp pacakes in a rash. So now I can not login server through ssh . what's worse, the server is a virtual machine, so I lost control on it. Can ...
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Slave interface receiving packets but not bond. Why?

I have 2 network interfaces with mac aa:aa:aa:aa:aa:aa and bb:bb:bb:bb:bb:bb When i bind them the bond gets the mac aa:aa:aa:aa:aa. I make a configuration where i make sure all the replies of icmp ...
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473 views

icmp redirect how to check if it works

I have seen on the internet many tips to disable icmp redirects. What I would like to know is how to properly check on windows and linux if it actually works? I have managed to spoof a fake icmp ...
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1answer
108 views

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 ...
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1answer
61 views

Windows Firewall log shows insane amount of ICMP SEND/RECEIVE requests. Normal?

I was checking my Windows Firewall logs after receiving a website notice that my connection was banned for sending too many requests, and noticed the following entries: 2017-05-18 03:39:23 ALLOW ...
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1answer
1k views

Centos7 disable IP Redirect sending on IPSec VPN Server

When using StrongSwan as an IPSEC S2S VPN Gateway, ICMP redirects are being sent to machines behind the right side. I have added the following lines to /etc/sysctl.conf: net.ipv4.conf.all....
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1answer
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Slave smokeping on xen VM shows substantial packet loss

I am using a Xen VM instance as a smokeping host. Recently I added a second XEN VM (on different iron, about 200 Km away) with smokeping in slave configuration. This is - again - a Xen VM, with a ...
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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:...
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1answer
165 views

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 ...
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346 views

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 ...
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443 views

Linux server icmp security

I have a Linux router, it is connecting to internet via pppoe with dynamic IP and I would like it NOT to respond to ping (or any other kind of icmp) from outside (internet), BUT I would like that ...
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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 ...
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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 ...
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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 ...
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1answer
46 views

Is there any way to scan host or network for icmp tunnel server?

I am looking for a tool that would be able to scan hosts for working on them iсmp tunnel server. For example ptunnel. I want to check hosts for which there is a lot of suspicion outgoing pings from ...
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1answer
777 views

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 -...
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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 ...
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1answer
140 views

Why would a host block ICMP echo (ping response) yet it allows me to connect to it?

Is there a security reason for that?
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419 views

linux ping incorrect source ip

I have a Linux box handling routing for my network. Here are some relevant configurations (public IP Addresses masked to 192.0.0.x): IP configuration: [root@gw ~]# ip addr 1: lo: <LOOPBACK,UP,...
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1answer
819 views

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 ...
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1answer
1k views

icmp ping reply not received by ping process, seen by tcpdump/wireshark

I'm having an issue with getting the actual ping process to receive the reply even though I can clearly see the response in the tcpdump output. I'm running on: Mac OS X 10.11.4 El Capitan Bridge ...
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Pinging (ICMP) Docker container on AWS ECS

I've got a script running in a Docker container that listens for ICMP packets. If you ping the container IP address, it picks them up and sends an email. However I'm having a bit of difficulty ...
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1answer
3k views

IPv6 - Allow incoming ICMP echo requests

So, we recently got our /48 prefix from our LIR, and started small-scale deploying it in a lab. What struck me as odd is that sites like http://ipv6-test.com/ insist that you allow incoming ICMP Echo ...
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1answer
424 views

How to use icmptx?

In Trusty (Ubuntu 14.04, both sides) I want to create an ICMP tunnel. I don't know how to set IP's. I searched and read some documents like this and this but I couldn't figure out what exactly I ...
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2answers
7k views

A non-recoverable error occurred during a database lookup

Short version: Why does Test-Connection report "A non-recoverable error occurred during a database lookup" for an offline host on a different subnet? I'm using PowerShell to ping a remote host with ...
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1answer
378 views

Manually sent ICMP redirect packets [closed]

I'm trying to sent a ICMP redirect to my router to add a new route, as I can not configure it from the portal, and have no access to it though telnet/ssh. The scenario is the next. LAN network 192....
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2answers
291 views

Do NATs rewrite ipAddress in payload of ICMP packets?

Today when I test running a tracert command (windows + Wireshark) I see a outbound ICMP_ECHO_REQUEST packet that has sourceIP as "192.168.1.55" - my local IPAddress. It is followed by a ...