Last call to make your voice heard! Our 2022 Developer Survey closes in less than a week. Take survey.

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.

Filter by
Sorted by
Tagged with
0 votes
0 answers
29 views

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 ...
user avatar
  • 1
0 votes
0 answers
32 views

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 ...
user avatar
1 vote
1 answer
51 views

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 ...
user avatar
  • 11
0 votes
0 answers
27 views

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 ...
user avatar
0 votes
1 answer
110 views

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 ...
user avatar
  • 11
0 votes
0 answers
32 views

Unable to add RDP to network created in azure, what is need to be added?

If I create a VM directly with azure portal and create new vnet,subnet and allow RDP from it. It is working. But if I follow below process, I am getting issue. I have created a vnet using below ...
user avatar
0 votes
1 answer
32 views

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 ...
user avatar
  • 115
0 votes
0 answers
13 views

iproute2 policy route same subnet wrong ttl value

I have a Linux PC has two NICs: 1st name is ens192, ip is 192.168.0.2/24 gw is 192.168.0.1 also default route, major NIC 2nd name is ens256, ip is 192.168.1.50/24 gw is 192.168.1.1, and with follow ...
user avatar
1 vote
1 answer
31 views

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 ...
user avatar
0 votes
1 answer
466 views

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 ...
user avatar
  • 1,017
0 votes
1 answer
254 views

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 ...
user avatar
  • 101
0 votes
1 answer
82 views

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 ...
user avatar
0 votes
1 answer
27 views

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 ...
user avatar
0 votes
0 answers
185 views

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 ...
user avatar
  • 101
1 vote
1 answer
71 views

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 ...
user avatar
0 votes
0 answers
337 views

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 ...
user avatar
1 vote
1 answer
228 views

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 ...
user avatar
  • 165
2 votes
1 answer
355 views

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, ...
user avatar
0 votes
1 answer
257 views

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 ...
user avatar
  • 113
0 votes
1 answer
308 views

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 ...
user avatar
  • 1
1 vote
1 answer
788 views

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 ...
user avatar
-2 votes
1 answer
253 views

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' ...
user avatar
1 vote
1 answer
230 views

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 ...
user avatar
  • 111
5 votes
2 answers
2k views

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 ...
user avatar
-1 votes
1 answer
2k 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 ...
user avatar
6 votes
1 answer
981 views

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-...
user avatar
0 votes
2 answers
1k views

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 ...
user avatar
1 vote
0 answers
153 views

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 ...
user avatar
  • 1,016
1 vote
2 answers
442 views

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 ...
user avatar
  • 13
0 votes
1 answer
462 views

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 ...
user avatar
  • 1
1 vote
1 answer
5k 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 ...
user avatar
  • 111
0 votes
1 answer
423 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.
user avatar
  • 53
-1 votes
1 answer
436 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 ...
user avatar
  • 715
-1 votes
1 answer
43 views

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?
user avatar
  • 103
1 vote
0 answers
49 views

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 ...
user avatar
0 votes
1 answer
220 views

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 "...
user avatar
  • 11
0 votes
0 answers
166 views

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 ...
user avatar
0 votes
1 answer
1k 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 ...
user avatar
0 votes
2 answers
939 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. ...
user avatar
  • 333
0 votes
3 answers
424 views

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)
user avatar
  • 333
2 votes
1 answer
1k views

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 ...
user avatar
  • 135
0 votes
1 answer
208 views

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 ...
user avatar
1 vote
0 answers
380 views

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 ...
user avatar
1 vote
0 answers
83 views

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 ...
user avatar
9 votes
2 answers
728 views

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 (...
user avatar
  • 1,383
0 votes
0 answers
68 views

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 ...
user avatar
-1 votes
1 answer
835 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 ...
user avatar
0 votes
2 answers
371 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 ...
user avatar
3 votes
1 answer
2k 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 ...
user avatar
0 votes
2 answers
55 views

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 ...
user avatar
  • 89

1
2 3 4 5