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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Why is it not possible to establish a connection between these servers?
I have the problem that my two servers (master, worker) can not connect to each other. However, connections outside e.g. "google.com" are possible. I have already tried to allow all ICMP ...
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Wierd firewalld block after recent update, Centos Stream 9, blocks icmp replies as invalid state
I am running Centos Stream 9 on VMware. I recently used dnf update and now there is a weird problem that some ping-replies are stopped by the firewalld. If I stop the firewall, ping works ok.
The ...
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Linux confusing MAC addresses for its IP addresses to Cisco switch?
I have multiple CentOS boxes (both Centos 7) with two different servers. These servers have 4 10GB interfaces each. They are connected to two Cisco Nexus switches. Each NIC has a different IP address, ...
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ICMP TTL exceeded replies with destination IP from NAT router
I'm playing with nftables and observe strange behaviour which I cannot explain.
I have three VMs, source, router and destination. All run latest Oracle EL 8.5 and are configured via nft.
source has ...
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How to identify application that is generating ICMP echo requests on Windows 10?
My company security team has informed me that my workstation is pinging some "blacklisted" IP addresses. The enterprise security tool reporting this information sits in place of the usual ...
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traceroute: sometimes routers don't respond and user sees timeouts
I'm an admin of small network and I'm investigating a problem my users complain about. The root of their complaints is traceroute: sometimes routers along the path simply don't respond to traceroute ...
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PMTUD/ICMP black hole problems across a VXLAN tunnel
I'm running a Proxmox PVE host and am trying to use VXLAN to connect the machines running on it to various networks in our Lab. However, I'm running into weird MTU-related problems that I don't ...
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Ping across IPSec tunnel sends both ICMP and ESP packets
I've been using Strongswan to setup an IPSec tunnel between two units. The tunnels SAs get setup without any issues and traffic can pass across the connection.
Whenever I ping across the tunnel, the ...
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Local devices aren't reachable via VPN
I have a VPN configured on a router (router model is bintec be.ip plus).
VPN Connections are successfully established by the clients using IKEv2 (router is reachable via DynDNS).
Router's local ip ...
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VLAN Inner Talking
I kinda forgot about CISCO in general, it had been quite a while since I last touched packet tracer. Now I'm on the PRE-deployment phase of a network at work. Long story short.
-I made 2 VLAN on CISCO ...
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ping: Warning: time of day goes back (-203647us), taking countermeasures
I'm getting the below weird warning message sometimes when pinging to 8.8.8.8 (Occurrence is very low). Any idea about the root cause?
$ ping 8.8.8.8
PING 8.8.8.8 (8.8.8.8) 56(84) bytes of data.
64 ...
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ICMP/Ping works even after adding iptables drop rule
We have an application which will configure network interface as well as iptables rules based on user configuration. Please find the iptables rules after configuring with the application
Even after ...
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Forwarding packets using multiple servers
I have a IP block from RIR.
I'm using two providers for make anycast to "some" IPs. I will call this as A and B.
I want forward to other provider when that IP not at that location. I'm using ...
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when router sends ICMP protocol error message how does it set it's own TTL?
when using (traceroute -q 1 serverAddress), we know that it starts with TTL(Time to Live) = 1.
when it goes through router, the router decrements TTL by 1. If TTL becomes 0 at that router, it sends ...
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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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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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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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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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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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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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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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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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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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