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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persistently disable ping/ICMP response on Ubuntu 20.04

It was possible to add net.ipv4.icmp_echo_ignore_all = 1 to /etc/sysctl.conf and reload with sysctl -p. This does work for me on Ubuntu 20.04. But after a reboot, the machine responds to ICMP requests ...
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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 ...
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When connecting from one subnet to another through a WireGuard VPN, why TCP requires NAT on both sides but ICMP works without NAT?

I encountered this issue today with the following setup: [Cloud Server] --> [Cloud Gateway Server] <- WireGuard -> [Home Router] <-- [Home Device] I have source NAT on my router. My home ...
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Sent type 3 code 4 with scapy won't update MTU

I have this configuration: H1<-->R1<-->H2 Beetween H1 & R1: Mtu set at 800 Beetween H2 & R1: Mtu set at 1500 Sending an ICMP too big from R1, generate an ICMP ERROR of Type 3 ...
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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 ...
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ICMP “Port Unreachable” when sending email

Since several months I have sporadic problems when I send emails. With tcpdump I finally found out that I'm getting "Port unreachable" messages from what seems to be my email provider, ...
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UFW Weird ICMP log record - Pinging is blocked

In the log records below I have replace my eth MAC address with ETH_MAC_ADDRESS the IP of my server with MY_SERVER_IP and other IPs with STRANGE_IP plus a number to distingue. Jan 29 15:11:48 cld ...
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iptables and SNAT spoofing

So we are working with iptables at class and I've been testing some rules in the NAT table. As far as I know SNAT changes the IP source of a packet to which the rule dictates but what I tested does ...
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Reset MTU with forged ICMP Type 3, Code 4 packet

I have four Virtual machines in this configuration configuration Router A and Router B are communicating each other beetween an IPsec implementation. So beetween them there is a tunnel up, and when A ...
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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 ...
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Firewall rules does not apply to pfsense hosted machine [closed]

I am using pfsense as my home firewall and configured multi-wan setup. In addition, I have installed package 'Telegraf ' package for exporting my pfsense stats into InfluxDB, also in 'Telegraf' ...
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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 ...
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Why 224.0.0.1 traffic is filtered by Linux hosts?

When sending an ICMPv4 echo request to a destination address like 224.0.0.1, it is ignored by Linux hosts receiving the request. The destination MAC address used is 01:00:5e:00:00:01. The only way to ...
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542 views

firewalld causing nmap to return host seems down

I've two machines, server1 and server2. On server2, I stop firewalld. [root@server2 ~]# systemctl stop firewalld From server1, nmap returns Host is up. [root@server1 ~]$ nmap -sn server2 Starting ...
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How to disable ICMP timestamp using ufw ubuntu

I am on a EC2 Ubuntu 18.04.1 LTS. I am running a scan using qualys. I am always getting a vulnerability warning about ICMP timestamp. I already follow this steps. I have configured iptables, ufw and ...
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ping receives DUP! response

A few weeks ago I was testing firewall / routing rules on a host, I initiated a basic ping and got a response I had not seen before, so I saved the capture. I seemed to be receiving duplicate ...
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Why does the rx counter doesn't increment when we ping our own ip interface?

When I ping my own interface ip address i.e. 169.254.30.242, I see that the tx counters increment but the rx counters don't. What is the reason that rx counters don't increment? $ ifconfig eth1 eth1 ...
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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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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 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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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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238 views

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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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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665 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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656 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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288 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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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 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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825 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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