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 isn't the internet broken?

I'm just trying to get my head round MTU, MRU and MSS. My interest initially came from the answer in this post: Security risk of PING?: Some ICMP packet types MUST NOT be blocked, in particular ...
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30 views

Can I ping a host that has disabled the ICMP Ping option?

I need to know if it's possible to compare and test how fast is an IP (ie: any web or game server) relative to my location (in terms of network latency), even if they have disabled ICMP/Ping requests ...
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Linux: Can user applications generate icmp messages?

I am using TOR and setting up a transparant proxy depending on users. I had trouble to constrain ICMP messages on UID. But I found an explanation for that on server fault. For the sake of privacy: is ...
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59 views

Cannot ping or ssh from lan to virtual machine

I have next setup: My home lan = 192.168.1.0/24 My virtual lan = 192.168.207.0/24 My laptop = 192.168.1.109 (dhcp OS=Windows7) My desktop = 192.168.1.206 (fixed ip OS=Windows8) My virtual machine ...
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43 views

UDP port scanning

UDP is connectionless, so I can't expect a response packet, necessarily. If the port is closed, I might get an ICMP error message, but if the firewall could silently drop the ICMP packet How could I ...
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26 views

What does this hex value mean in source column within NETMON?

I am using NETMON to try and figure out why my local network is running so slow. I think it may be related to a system logged into it, but in order to not draw attention to my task i have been ...
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595 views

udp client sending ICMP “port unreachable” when receiveing messages from the server

(Note: I moved this question from StackOverflow, because it's to be considered off-topic there, better fits here, and still unsolved) I have a udp client using luasocket, basically doing this (with a ...
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246 views

SSH and PWNAT for SSH Connection Between Two Separate NATs

Is it possible to use pwnat and SSH to establish a "peer-to-peer" SSH connection between two machines that are behind two separate firewalls/NATs? If this is possible, what are the steps that would ...
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What is the purpose of using a large ping packet?

While analyzing some traffic logs, I noticed a node pinging its gateway with a large ping packet size, ranging from 700 bytes to 1 MB. It's a constant ping from node to gateway and the size per ping ...
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No response to ping of specific size

ping <anything> -s 473 does not receive a single reply. ping <anything> -s 476 works, as well as ping <anything> -s 472 but no size inbetween. What could be the reasons for ...
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176 views

Batch Capture incoming Netstat IPs as variable

I'm trying to figure out if there is a way I can capture (and if possible, log) the ip addresses displayed from 'netstat' command. I'm trying to make a script that waits for a ping from a specific ...
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197 views

Router keep advertising itself on ipv6

I keep receiving the following router advertisement every few seconds from my router on ipv6 despite disabling my wireless ipv6 connection: # tcpdump -vv 'ip6 and icmp6' tcpdump: listening on wlth0, ...
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21 views

How to create ICMP Code-3 error

I made lots of search but couldn't find useful info about how create ICMP Code-3 (dest. unreachable) error and capture it with Wireshark. I tried to ping a closed port in Linux machine and also used ...
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77 views

Why does Windows use the same identifier for different ping sessions?

I noticed while debugging some NATing issues at work that Windows (Windows 7 in this case) echo reply and echo responses are always setting the ICMP identifier field to the same value regardless of ...
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202 views

Wireshark Capture Filter

I am new to wireshark and I am trying to capture an ICMP packet over 802.11g, I am using windows and pingplotter. The issue is that on wireshark capture I am not getting any ICMP packets no matter how ...
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174 views

Make ICMP exempt from IPSec protection

I'm reading a reference book on Microsoft DirectAccess. It contains the quote: To use Ping as a troubleshooting tool, ensure that Internet Control Message Protocol (ICMP) is exempt from IPSec ...
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73 views

ICMP Fails after first packet

I'm trying to ping any ip, other than my LAN IP & localhost, it fails except the first packet!! Snapshot from CMD with the pings But Wireshark capture shows that the ICMP is success!! ...
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191 views

OS X: how to make it reply to “ICMP time stamp query”?

As per another question, I'm using hping--icmp-ts to send the ICMP time stamp requests to debug asymmetric routes. It seems like my OpenBSD box generates time stamp replies by default without any ...
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3k views

How do I forward traffic between Tun device and eth0?

In summary, I would like to have Tun device traffic forwarded back and forth through another network interface that has internet connection. While I can see the traffic going out to internet ...
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7k views

what is type of ICMP packets? TCP or UDP

ping packets is a type of ICMP packets.Is there any relation between ICMP with TCP.In other can we guaranty their arrival in the network I want to know ICMP packets in the network is tcp or udp or ...
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50 views

ICMP over protected wifi

I am looking at sending a single ICMP message to a server and recieving one single ICMP reply. The question that I'm trying to answere is if it is possible to send an ICMP ping over a wifi that i do ...
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77 views

How to inspect DSL router? [closed]

There is a DSL connection and a DSL router (Speedport W 701V). After some days or weeks (I didn't record the events) the router makes some problems. Internet connection is ... broken but not ...
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ICMP firewall policy for standard ubuntu desktop

For a standard desktop computer running Ubuntu 12.04 behind a NAT router, what ICMP packets should one accept in the firewall, say iptables? It seems there is often conflicting advice; some say block ...
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1k views

How can I block ICMP/PING/Traceroute on Mac OSX Server?

I understand that on Linux I do: // allow echo 1 >/proc/sys/net/ipv4/icmp_echo_ignore_all // block echo 0 >/proc/sys/net/ipv4/icmp_echo_ignore_all // permanent block (edit /etc/sysctl.conf) ...
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Is it allowed to Ping Backbones or other ISP Servers for a prolonged pingtest? [closed]

I made a few Ping tests until now, once I made it a whole week, but now I'm not so sure about the thoughts of the Admins which are owning the servers I ping. Now, I have found a few posts which are ...
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What are reasons to disallow ICMP on my server?

An EC2 Instance has ICMP services disabled by default. While it's not totally clear to me why, I think it's because it could be a potential security risk. At the moment I'm enabling Echo Responses ...
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519 views

Why am I having trouble using ptunnel to connect to machine in DMZ from WAN?

I'm trying to have a play with ptunnel, I have it running (listening) on my raspberry pi in my DMZ and I can connect to it from my LAN and tunnel ssh over it, but I can't get it to work over my LAN. ...
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ICMP redirect: how to test it with icmpush

I want to see how the routing table changes on a Linux system, when an ICMP redirect is received. For that I use icmpush -v red -sp current-gateway -gw new-gateway -dest google.com -c host -prot tcp ...
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Windows ping - 'ignores' ping replies

I'm using Window's built-in ping command to test connectivity with my Ethernet device ( a enc28j60 Ethernet controller and an avr atmega), but Windows ignores replies. Screenshots :- ...
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104 views

traceroute on Linux displays '* * *'

What is going on? If I run traceroute google.com it outputs 192.168.0.1 for the first router (which is correct) and threee *'s for the rest. I have tried disabling the FireWall on the router ...
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751 views

Firewall blocks ICMP even with Allow rules, even when disbled

Sometime early October (right after update Tuesday???). My Window 7 home machine stopped responding to anything incoming. Effectively breaking iTunes, Sonos, TiVo Desktop, RDP etc. But all those ...
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Is there a way to test alternate IPv4 routes?

i am using Hurricane Electric's Tunnel Broker service to get IPv6 connectivity. TunnelBroker lets you have access to the IPv6 Internet by using a standard IPv6 tunneling protocol. You send IPv6 ...
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Filter ICMP packets sent from my IP address in Wireshark with the Packet Filter

I want to filter the ICMP packets sent from my IP address in Wireshark. I tried the following expression: ip.src == xxx.xxx.xxx.xxx && icmp But the problem is that it shows packets with ...
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How is ICMP unique?

I just read this in Wikipedia: Although ICMP messages are contained within standard IP datagrams, ICMP messages are usually processed as a special case, distinguished from normal IP ...
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225 views

Traceroute to IP address fails, but traceroute to domain name with same IP address is okay. Why?

When I traceroute to this IP (108.162.198.181) it stops after 1 hop. But tracerouting to a domain (www.gomodule.com) with the same IP shows 9 hops ending in that target. traceroute to ...
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593 views

test of ICMP block

In my bash scripts I have been using something like: until fping -u google.com; do echo "$0[$$] Network/DNS down?? $(date)" 1>&2 && sleep $(($RANDOM%(1 + ++trynum * 1) +1)).222; done ...
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What could be causing problems on pinging Windows 8 machines?

Here at my job I have 5 machines with Windows 8 Consumer Preview installed on it. Today I was testing the network conectivity and any of the 5 machines answered to a ICMP ping request(but from another ...
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1k views

Difference between TCP and IP tunnelling?

Can someone please explain in terms of the OSI (or TCP/IP) layers, what is the difference with what goes on when you tunnel IP or TCP, say over the ICMP protocol (although the latter doesnt really ...
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604 views

ICMP Tunnelling IP vs Tunnelling TCP?

Could someone please explain the difference between tunnelling IP data using ICMP packets and tunnelling TCP data via ICMP? Obviously I know this is going to be something relevant to the different ...
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270 views

How to use ICMP to verify the accessibility of a site?

If I want to know for sure that a web site is really blocked by the authorities or the site itself faking it, what kind of a method can I use..? I mean that when we use tracer it just use the ICMP... ...
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Linux: How to monitor incoming pings

Can I somehow monitor incoming pings on a Linux machine? netcat doesn't seem to support that.
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4k views

What is ICMP broadcast good for?

To configure Linux to ignore ICMP broadcasts (to protect from SMURF attacks), I have added the following line to /etc/sysctl.conf: net.ipv4.icmp_echo_ignore_broadcasts = 1 Anyone knows what are the ...
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2k views

Is it possible to tunnel ICMP over TCP?

I don't want to tunnel TCP over ICMP (as ptunnel does), I want to go the other way around. I'm in the situation where I have TCP (HTTP) connectivity to a machine but an internal firewall over which I ...
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1k views

Process does ICMP port scan on my OSX box and I am afraid my Mac got a virus

I noticed that my 10.6.6 box has some process sending out ICMP messages to "random" hosts, which concerns me a lot. when doing a tcpdump icmp I see a lot of the following 15:41:14.738328 IP macpro ...