Questions tagged [icmp]
For questions about the Internet Control Message protocol.
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How do ICMP packets travel in a networks?
Questions:
I'd like to know how ICMP packets travel in a network? Are they encapsulated within IP datagram?
The RFC 792 doesn't explicitly states the layer of ICMP. Are ICMP messages sent using a ...
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Why doesn’t ICMP use port numbers?
Firewall is showed in port no 7 and Google search is also showed in port no 7 so I am confused about how exactly ICMP use the port number.
Regards,
Bhushan
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How do I permit only specific types of ICMP unreachable packets to be sent out from a Cisco IOS router? [closed]
I have a Cisco IOS router and want to permit only types of ICMP packets to be sent (type 8, code 0 and type 3, code 4). I tried putting an outbound ACL on the interface connecting to the Internet, but ...
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When is 'Timestamp' and 'Timestamp Reply' are used in ICMP protocol?
I started the packet capture in my laptop through Wireshark application.
Now through cmd, I pinged some server (say, www.google.com).
And i stopped packet capture and analysed the packets being ...
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Pinging a host that is not on
What happens if I send a ping to a host that is off? Do I get an ICMP message with "host unreachable"? Does ICMP say nothing at all because the packet was correctly delivered even though it was not ...
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Ping traverses openvpn tunnel only 1 of 2 times [closed]
I can barely put into words the problem I'm having, but I'll give it a go.
I have a pfsense router on which I've set up openvpn to act as a client to connect into another network.
This has worked ...
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Spoofed Tunnel Route
What does it mean when tracert always shows a single long jump?
The route below is always the same except the last hop goes
directly to any destination IP address that I choose.
And, how does the ...
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Weird results when pinging
I'm learning IP addressing and routing basics, but I'm facing a problem which I cannot understand, so i have the following structure:
Well in this situation, a ping from 130.190.0.16 to 130.190.4.30 ...
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Is there any current use of icmp features like Address Mask Request
I recently looked through the ICMP packettypes and there are some packettypes which in theory allow to request information from a host like the domain name, subnetmask, timestamp,... out of curiosity ...
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Why can I ping IP addresses from 127.0.0.1 to 127.255.255.254?
I thought that the loopback IP address of my machine is 127.0.0.1.
I do not understand why am I able to ping IP addresses until 127.255.255.254.
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Traceroute program that does not rely on ICMP echo requests?
Is there any Traceroute program that does not rely on ICMP echo requests?
The question is very straight forward, and I can't get into more details at the moment.
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Fingerprinting routers using timestamps
We all know that physical machines can be fingerprinted using timestamps of a clock in the NIC. My question that is it possible to fingerprint/uniquely identify routers based on timestamps?
If yes ...
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How to disable ICMP type 9 (router advertisement) on SG300
Oddly enough our cisco SG300's are making "Router Announcements"/"Mobile IP Advertisements" (ICMP type 9) via IPv4 (not IPv6). They are sourced from the IP/MAC of the switch and destined for 224.0.0.1/...
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How do i clear icmp statistics (JUNOS)
I run a rapid ping and then run show system statistics icmp
I want to run another ping test but how do I clear out the old stats?
clear interfaces statistics all does not clear out the icmp stats
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How to choose TTL value
When viewing the result of a ping request, I always see the TTL value (Time To Live) of the package. As most of you know, this value is used for avoiding endless looping in the internet routing ...
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Difference of tracert and pathping
What is the difference between tracert and pathping command? Thanks
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ARP broadcast vs Default Route
Assume a host is connected to a router. If a host pings an unknown unicast address that's not in host's routing table, which one of the following is going to happen? (Assume the default route points ...
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Ping Port Number
I'm just wondering, is there a port number used for the ping command. I have dissected the ping packet on Wireshark, but I haven't seen any destination or source ports. Am I just missing something?
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Trace route does not complete and applicatin fails to connect but website works in browser [closed]
I am trying to narrow down a problem with intermittent connectivity issues to a remote service hosted via HTTPS. The application frequently fails to establish the SSL tunnel during the CONNECT phase.
...
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CRC errors and ICMP packets loss correlation
I would have a question regarding physical problem detection in a link with ping.
The assumption is as follows: I have a fiber or cable with much of noise due to bad hardware (bad cable or bad ...
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Ethernet padding
I'm using Wireshark for my project. I sent a ping over to Google.com and Wireshark said that the length was 57 bytes(when I received the reply it was 60 bytes long and it contained 6 bits of padding.
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ICMP Ping Request/Reply
I try to ping something out with a PC/Router IP address 10.57.1.2 with the following Ping Request and Ping Reply received
Ping Request
Source 10.57.1.2
Destination 192.168.31.10
Reply
source ...
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PING port number?
Yesterday interviewer ask me what is port number for ping and which protocol ping use TCP/UDP.
After interview I search on internet and found different results someone says ICMP uses Port 7, someone ...
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Does there exist a difference between ICMP Destination Host Unreachable Message from MacOS/IOS and from Windows/Ubuntu? [closed]
Information
I have recently been learning networking programming with Python, and I am now building a host scanner utilizing the ICMP Destination Unreachable Message.
Indeed, I have partially ...
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Initial ping failure in Packet Tracer
In Packet Tracer 7.0:
After directly connecting two switches or a router and switch, pinging the neighboring device always fails on the first one or 2 attempts (i.e. only 4/5 or 3/5 ping attempts are ...
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Forbidden icmp package between hosts?
I have 2 hosts, called client1 and client2, connected with a switch and this switch with another host called firewall, having access only with firewall.
Is it possible to forbid ping between clients? ...
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Default Gateway Best Practice
Recently I was troubleshooting a firewall issue on one of my servers and noticed that there was a LOT of ICMP redirect traffic being rejected (as it should be). But this got me thinking why I was ...
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What high level (above IP) protocol is used to return a response to an ICMP echo request?
I know ICMP uses IP datagrams to reply to echo requests but what is above that?
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Time exceeded ICMP in Serial Interface [Cisco Router 2811]
R1 and R2 are the same network.
But when you send a check to the ICMP Ping output "Time exceeded" error and,
show interface Serial0/0/0
command produces the following output:
Serial0/0/0 is up, ...
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More Information from ICMP & ARP
I installed DEKSI Network Administrator Demo and when it is Creating Map, in Step 3 of 4. Searching and selecting hosts for placing on the map, it found IP address and Mac perfectly, but it also found ...
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Is using traceroute with ICMP echo messages valid?
Theory says that there shouldn't be any ICMP error messages for ICMP messages. When sending ICMP echo requests in traceroute, doesn't this break this rule?
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Types of packet loss
I am used to the term ICMP Ping Packet Loss but recently, I came across this other term UDP Jitter Packet loss
I will like to know the difference between the two, and of what importance it is to ...
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Checking the binding of IP/MAC addresses for a device
As a network administrator, assume I want to check IP/MAC binding of a certain device in my network to check if the binding has been changed or not (Since my network does not have DHCP server and ...
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What header fields in IP, TCP and ICMP packets do NOT get altered in general by firewalls and NAT/gateways, both state-ful and not?
I need to determine which header fields in IP, TCP and ICMP packets will never (at least, in 99% of cases, excluding perhaps a bizarre overly-aggressive firewall) be altered by a firewall or NAT/...
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How to find out TCP/UDP latency of your network? [closed]
Many people often suggest you to use ping command to find out your network latency. But it is false and a myth you often find in articles on Internet.
ICMP ping was never designed to find out latency ...
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cisco7200 router responds to icmp messages not addressed to it
I am trying to play (in GNS3 if that matters) with a very simple topology of three routers connected via hub. The time I am trying to ping from one of the router to another say R1 to R2. The R3 ...
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ICMP Fragmentation
Would a ping (echo request) to a reachable IP address with a size of 65500 bytes, end-to-end path MTU of 1500 Bytes, and the DF flag not set, work by having the peer responding an ICMP?
21:05:31....
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HTTP server responds with TTL- exceeded for TCP-SYN till TTL is increased by +2 from the actual number of hops
Trying to traceroute an HTTP server using TCP-SYN packets. There are 13 hops between the two hosts, but the server responds with TTL-exceeded for TTL=13 and TTL=14. It replies with TCP SYN-ACK only ...
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ICMP TTL-exceeded header shows Length: 243 [Length of original datagram: 972] in wireshark. Original TCP-SYN was 58 Bytes
TCP SYN for traceroute
ICMP header shows
Length 243
[Length of original datagram: 972]
Not sure how this works, as I sent a TCP-SYN of 58 Bytes frame. Please explain
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Difference between ping timed out and destination host unreachable
I'm pinging from a Windows Box to a device that I rebooted.
PS C:\Users\administrador> ping 192.168.2.10
Pinging 192.168.2.10 with 32 bytes of data:
Control-C
PS C:\Users\administrador> ping -...
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How are ping times computed
I have been graphing ping (IPV4) responses times/vs packet size. I was expecting to see a discontinuity of around 2*MTU/BandWidth in response time around the MTU boundary (actually, around 1464 byte, ...
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Firewall seems to damage/delay packages
I have two networks communicating with each other through a transparent firewall. My problem is that the software using these networks is reporting that it's losing packages. The number of lost ...
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Decrease the Router's buffer size
Through this topology, I want to decrease the buffer size of R2 in order to generate an ICMP Source Quench Message, but I have no idea how to do it. I'm open to other suggestions to generate a Source ...
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Telnet - "Destination unreachable" response
I'm looking to implement, what I feel, is Telnet security when it comes to unwanted hosts initiating a Telnet connection to one of my devices.
I can lock down a specific subnet or only allow a range ...
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ping server vs. connecting to server
Networking newb here. Under what circumstances could you fail to ping a remote server with the ping command, but still be able to connect to it via other means (as long as it was still TCP/IP)?
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Strange router's MAC address from ICMP Echo Reply?
Using Wireshark to capture ICMP packets (Windows) using ping to google.com, I can see the source-MACAddr of the ICMP Echo replies is not the same as the MAC address of my direct router (which is the ...
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What kind of packets do tools like nmap use to discover other hosts on the network they are scanning?
There are lots of tools like nmap and I am using one for android that discovers every (?) host on the network that I am connected to. I do not understand what kind of packets are send by the program ...
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Mystery ICMP Packets from HP 2910 Switch
We have a pair of HP 2910al-24G switches that are used internally at one of our locations. They are both updated with the most recent firmware and software and are operating fine.
During a routine ...
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Why is the ICMP protocol considered to run at layer 3 on the Wikipedia page?
Why is the ICMP protocol considered to run at layer 3 on the Wikipedia page (same layer as IP) when the ICMP protocol data is a payload of the IP packet?
This is the article on Wikipedia that states ...
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