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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How to send a custom ICMP reply message for a ICMP request message using Scapy tool?

I am using two ubuntu VM's and I am trying to send one ICMP request packet from one VM to other and I got a reply which is automatically generated by the system. Now I want to generate a custom reply ...
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ICMP BURST reported What option to check initial level

In case ICMP Burst reported and the source of ICMP request is the Server xx:xx:xx:xx where Application deployed. What Action to perform? /Suggestion. Disable ICMP Or Is their option to block this at ...
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How to generate ICMP response

I am trying to test various scenarios related to ICMP and for that, I need to generate multiple ICMP responses. For testing my flow I need ICMP response "TTL expired in transit or Fragment reassembly ...
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Router receives ICMP requests for reverse IP

I have a router connected directly to my ISP's modem which provides me with several public static IPs, say 99.88.77.105/29 where 99.88.77.110 is the assigned gateway. With all firewall rules in place ...
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Can't ping EC2 instance after enabling ICMP packets [closed]

I followed this guide to allow me to ping my EC2 instance. In my security group I have Custom ICMP Rule - IPv4, Echo Reply, N/A, Anywhere. However it simply doesn't work. If i run ping ec2-X-X-X-X.ap-...
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How do I limit ping (ICMP) responses on a debian 10 server?

I have a VPS with debian 10 installed, primarily used for website hosting. when I issue a ping to the server from a remote machine, I am able to and receive responses for packet sizes up to around ...
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Difference between icmp and icmpv6 for ip6tables?

I found the following lines in a firewall script on one of our Linux servers (kernel 5.x) ip6tables -A INPUT -p icmp -j ACCEPT ip6tables -A INPUT -p ipv6-icmp -j ACCEPT The two commands both run ...
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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 ...
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DNS responses within ICMP Port Unreacheable packets

I am analyzing a traffic dump in which there are some standard DNS queries but their responses are in ICMP packets. The structure of these ICMP packets is; IP->ICMP->IP->UDP->DNS(response) say ...
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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 ...
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How to stipulate ufw ICMP/ping rules from the ufw(8) command line in Ubuntu Linux?

How can one stipulate the following ICMP/ping-oriented rule (which works when inserted into /etc/ufw/before.rules) from the ufw(8) (UncomplicatedFirewall) command line instead of the /etc/ufw/*.rules ...
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721 views

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 ...
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88 views

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.
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Whitelist ICMP traffic with iptables

I'm configuring iptables, for an Ubuntu Server VPS. It runs sshd, and various Dockerised web apps. It is not a router, and is not part of a complicated network. After researching the topic, I decided ...
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ICMP types commands on CMD?

To use ICMP type 8 we write : >ping IP@. I was wondering what commands would allow me to use other types of ICMP like type 13?
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SmartOS can't ping any ip that resolves to failover ip

Our server is running SmartOS, we have 2 network cards one for internal use (10.x.x.x) and one external, i am able to ping any website / service except domains that resolve to our Failover IP (The IP ...
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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 "...
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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 ...
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609 views

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 ...
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407 views

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. ...
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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)
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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 ...
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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 ...
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How to allow responding to broadcast pings on Mikrotik RouterOS?

By default, most systems don't respond to broadcast ping requests. However, there exist ways to explicitly allow responding to broadcast ICMP requests on multiple systems, such as Linux. How can I ...
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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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363 views

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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177 views

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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764 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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165 views

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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227 views

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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560 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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148 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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593 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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70 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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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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788 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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168 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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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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2k 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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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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