Questions tagged [icmp]

ICMP is the Internet Control Message Protocol. It is used for diagnostic purposes, for querying information, and for transmitting network-level error messages. ICMPv6, the version for IPv6, is also used for configuring nodes on the link.

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iptables: how to block traceroute and allow ping?

Hi first sorry for my english. I'm trying to block traceroute --icmp (tracert) while still permitting the ping, using iptables. The problem is that when I permit the traffic of echo request, to allow ...
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Pinging default gateway on a Linux virtual machine

I have two question about the network. I started to ping my router from my Linux virtual machine and I have intercepted these ICMP frames. I noticed that the destination MAC address is not my router ...
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entry in arp table present but still requests

Working with a linux machine and a microcontroller with the lightweight IP stack on it. Trying to get a ping going between them and facing some issues. The first time when a ping is initiated from the ...
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Prevent SNAT rules in iptables from being applied to ICMP time exceeded packets?

I have the following rules on a Linux server, to route packets from LAN node 10.0.1.8 (a Windows machine) destined for 192.168.173.93 to 1.2.3.4 and vice versa: iptables -t nat -I PREROUTING -i br0 -...
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View packet data of ping

Is there a flag or other utility (perhaps tcpdump?) that can be used to see the outgoing packets that are sent via the ping utility? For example: $ ping -c 5 google.com PING google.com (172.217.14.78)...
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How to allow icmp for your machine? [closed]

I want to allow icmp (ping) for my server. I was reading about IPTables and read that to allow a ping to your machine, you need to have INPUT rule as well as a FORWARD rule. Because INPUT only handles ...
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Tcp connection packets ignoring network delays, ping shows delays [closed]

I've introduced a 2000ms latency to all network packets using openwrt netem module. # This is run on the terminal of the OpenWRT router tc qdisc add dev wlan1 root netem delay 2000ms I can clearly ...
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Host unreacheable from laptop but reacheable from desktop

I have a Synology NAS at home (let's call it ananas), it is attached to my router via ethernet. I also have a desktop (let's call it Aero), it is connected to the same router via wifi. I configured in ...
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Iptables rules enabled for allowing icmp/ping for only specific IP address with RHEL7 OS not working [duplicate]

The server where iptables rules are enabled is RHEL 6.4. From this server, I tried to allow icmp echo request from only one specific IP address (host with RHEL7.5 OS). I used the following rules: ...
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How can I ping multiple IP addresses at the same time?

I'm aware of the methods where you can run a Bash for loop and ping multiple servers, is there a Linux CLI tool that I can use which will allow for me to do this without having to resort to writing a ...
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TAP/TUN capturing ICMP packets

I'm trying to capture raw ethernet packets into a user space program. Having read about the TAP/TUN capabilities of the kernel, I went on and created the following setup: Two systems connected ...
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ICMP “TTL expired in transit” and “Fragmentation required” messages when forwarding is disabled

I have a server with IPv4 forwarding(routing) disabled: # sysctl net.ipv4.ip_forward net.ipv4.ip_forward = 0 # Is there a circumstance where such server sends out ICMP 11/0(TTL expired in transit) ...
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Tunneling TCP via ICMP slowness

There is: Server "A" Server "B" I have root permission on both. They can ONLY ping each other. I installed ptunnel on both. On Server "A", I tried to: ptunnel -p SERVER-B-IP -lp 6969 -da SERVER-...
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How to view ICMP Redirect Logs

I have read on multiple sources that there is are logs for rejected ICMP redirect messages, one of them being "Understanding Linux Network Internals: Guided Tour to Networking on Linux" By Christian ...
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Should I remove ICMP Protocol from firewall rules base on security concern?

As you can see from the screenshot of GCP firewall rule page, should I remove ICMP Protocol from firewall rules base on security concern? Will it lower the chance of being attacked? I'm using CentOS ...
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How come one can successfully ping 127.0.0.2 on Linux?

On a FreeBSD system with a loopback network interface … % ifconfig lo0 lo0 link up loopback drv_running running multicast nd6 performnud auto_linklocal no_radr link rxcsum ...
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855 views

It is possible to traceroute without touching ICMP?

I often run into a situation where I want to traceroute an IP without root or NET_RAW cap in Linux. I have attempted to send a UDP packet with a small TTL but no ttl error is emitted at all. It seems ...
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774 views

How to Disable Ping ( TCP ) in Linux all the time? [closed]

I want to disable ping response all the time. I use the following command for disable ICMP ping iptables -A INPUT -p icmp --icmp-type echo-request -j DROP what should I do for disable TCP ping ?
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Exclude interface when send ICMP ping

for build small linux application I need to check the internet connectivity of the system. But my box have multiple network interfaces with interfaced for backup internet connection. I need to do some ...
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532 views

How to check whether kernel received MLD query or not?

On the Internet I found this command netstat -p icmp6 -s which can dump how many MLD queries received by the kernel. But I have Busybox for my system and because of this I'm unable to run netstat ...
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mtu 9000 issues only on tcp and not icmp possible?

I have a connection between two datacenters and rsync between them stalls often. I think it is related to the mtu 9000 (I actualy set it to 8900 because of some possible vlan use) I have the ...
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What Linux process is responsible for responding to pings?

I have a Linux based process controller that occasionally locks up to the point where you can't ping it (i.e. I can ping it, then it becomes no longer pingable without any modifications to network ...
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I have disabled all rules in firewall, but still can tracert from LAN

I have disabled all positive rules in firewall on my pfSense box, and I can't browse Web, but I still can tracert 10.10.0.251 from LAN machine and receive 3 hops from my ISP (behind the router). ...
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tcpdump -i any doesn't work on FreeBSD

How to listen all interfaces on FreeBSD with tcpdump > tcpdump -i any tcpdump: any: No such device exists (BIOCSETIF failed: Device not configured) (I would like to listen ICMP)
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UDP port unreachable although process is listening

I am experimenting with communication over UDP port 6666 (the goal is setting up a listener for netconsole, but that's not really relevant here). On the listening side, nc -luv 6666. On the sending ...
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How to Disable Ping Response (ICMP echo) in Linux all the time?

I want to disable ping response all the time on my Ubuntu operating system, the following commands work but only until the system reboots: Ping off: echo "1" > /proc/sys/net/ipv4/...
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Reading MLDv2 queries using an IPv6 socket

I have mrd6 installed on my raspberry pi. It registers with a local interface (tun0) and periodically transmits MLDv2 queries over it. According to [RFC3810], MLDv2 message types are a subset of ...
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No buffer space available - ICMP

I'm trying to set up a Heartbeat client on a linux machine (CentOS Linux release 7.3.1611) which is sending ICMP echo requests to roughly 1300 hosts. However, in future this number will be higher. The ...
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Network Interface VLAN static addressing

I have been trying to configure the static IP addresses with Ubuntu 16.04 Dabian version. The network as follows in the graph I have been failing to ICMP (ping echoing) between the Client and the ...
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What is ICMP reply for all-zero host-bit IPv4 address?

We all know that the first address of any sub-net is network identifier and it can't be assigned to any hosts. For example in network 10.1.1.4/30, the address 10.1.1.4 is network identifier. If ...
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How to DROP icmp requests with firewalld?

How to DROP icmp requests with firewalld? An equivalent example instead using iptables would be: $ iptables -A INPUT --protocol icmp --in-interface enp0s8 -j DROP The above produces the desired ...
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How to configure iptables ICMP rules on a router?

I'm trying to configure iptables rules on a router that allows ICMP (PMTU-D, ping, traceroute, etc.) to function. GOALS: 1) Allow all ICMP outbound traffic initiated from the router and internal ...
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How to make Linux stop sending IPv6 ICMP redirects?

In case of IPv4 we have net.ipv4.conf.all.send_redirects flag, but it's not available for IPv6. Is there anything better than this? ip6tables -A OUTPUT -p icmpv6 --icmpv6-type redirect -j DROP For ...
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885 views

MTU (IPv4) tests in Linux

I noticed I have several networks with all ICMP messages blocked at the firewall level, except for ICMP echo and reply. I know that there is a need at least ICMP messages type 3 in IPv4 have to be ...
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How to disable ICMP timestamp on AIX - not using firewall

On AIX 6/7 how can we disable this function? I cannot see any in "man no". Installing firewall just because of this is not really an option.
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Only ping fail output should get visible

Is there a possibility for getting only the error output when running the ping command? Its very tricky to understand if we have n number of server monitoring. icmp_seq will obviously show the drop ...
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iptables REJECT with delay

Simulating an unreachable host: iptables -I OUTPUT -d 192.168.1.42 -j REJECT And then ping 192.168.1.42. It rejects immediately, so the terminal is flooded with Destination Port Unreachable. How to ...
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Forward ICMP Ping Packets to Interface

I've got a script that listens for ICMP ping packets (containing data payload) and while this works if you run it from command line, it doesn't work in a Docker container because ICMP ping packets are ...
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ICMP - Destination unreachable (Port unreachable)

I have two Ethernet-wired connected devices. I gave to both of them address from same sub-network. As result I can see second device in arp-table of the first. $ arp -a ? (128.247.77.90) at 10:60:4b:...
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Can two android devices in different network(3g) comunicate themselves with ssh connection?

I have two rooted android devices with different isp (I use different 3g connection for them) and created a double ssh connection (I can with a public ip server) communicating both to this server (I ...
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621 views

iptables REJECT icmp-admin-prohibited

The iptables man page says: Using icmp-admin-prohibited with kernels that do not support it will result in a plain DROP instead of REJECT I have been unsuccessful at finding out at which kernel ...
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How to accept ICMP redirects?

tcpdump showed me there are some ICMP-redirect in my network (KVM virtual-machines, bridged network). I decided to take a closer look on them and how my system behaves and how it looks. I found it ...
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Subnet routing problem

In my LAN I have an openwrt router configured with IP 10.0.0.1. It is the default gateway (and dhcp server) in my LAN 10.0.0.0/24. Now I have a new network, say 10.9.0.0/24 used by virtual machines. ...
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ICMP : Port unreachable error even if port is open

I am testing my Debian Server with some Nmap port Scanning. My Debian is a Virtual Machine running on a bridged connection. Classic port scanning using TCP SYN request works fine and detects port 80 ...
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How to get different types of ICMP

I have a task on which I have spent a lot of time. I am not fluent in Linux, but I can manage basic things. The task is to gather different types of ICMP packets. I can harvest them by tcpdump (which ...
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How to disable IPv6 ping response in Linux without firewall

How can I disable IPv6 ping responses in Linux without using the IPv6 firewall? This question covers how to do this using the IPv6 firewall via iptables, but I'm using an embedded system that doesn't ...
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1answer
207 views

IPV6 ND router advert Malformed packet

Am trying to simulate IPv6 ND router Advertisement packet in openvswitch for one of my projects, but the formed packet is malformed(analyzed it in wireshark). Following is the packet dump I created, ...
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1answer
668 views

Some ICMP-Reply messages don't arrive in User Space in recent Kernels

I'm moving an application from 2.6.23 (yes, it's ancient; that's why we are moving) to 3.18LTS. The application monitors multiple network links to the same target with ping packets. The different ...
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445 views

Drop all ICMP packets?

Is it ok for me to drop all types of ICMP packets? I.e. iptables -I INPUT -p icmp -j DROP. Everything except one service seems to work. I already stopped this service. To be specific I functioned as ...
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Why is a Linux Tun interface not returning ICMPv6 Echo replies?

I wrote a program which connects to a TUN interface and replies to ICMPv6 Echo Requests. Even though I can successfully observe the echoes and replies with tcpdump on the TUN interface, it appears ...