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For questions about the Internet Control Message protocol.

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2answers
34 views

Whether the traceroute command only can check “to” path, can not check “back” path?

How to detect the router path of traffic? I use the ipip.net for ICMP traffic: I want to check the out path and back path. such as I have A address 60.248.41.135 and B address 103.248.41.135. ...
4
votes
1answer
51 views

Features of ICMP

I'm taking a Network class and learned ICMP, but I cannot understand the reason why below arguments are applied. ICMP message is not generated on header checksum errors If a datagram carrying an ICMP ...
4
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2answers
343 views

Why there are ip(ip) and domain(ip) 's difference and multi rows records in the traceroute?

In the traceroute command: $ traceroute 104.43.54.2 traceroute to 104.43.54.2 (104.43.54.2), 64 hops max, 52 byte packets 1 10.10.10.1 (10.10.10.1) 4.852 ms 4.623 ms 1.588 ms 2 100.64.0.1 (100....
7
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2answers
2k views

Where is Ping's “round-trip time” stored in the IP header?

If we use ICMP's ping, we know the TTL and round-trip time are stored in the IP header. In the below IP header map we know TTL's location, but where is the round-trip time? Is it stored in Options?
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2answers
52 views

CRC done by ICMP?

Is cyclic redundancy check (CRC) done by Internet Control Message Protocol(ICMP)? How can Time to live (TTL) help for this?
0
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1answer
94 views

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 ...
1
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6answers
1k views

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
3
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1answer
145 views

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 ...
1
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3answers
453 views

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 ...
1
vote
2answers
35 views

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 ...
0
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2answers
109 views

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 ...
1
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3answers
74 views

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 ...
0
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3answers
102 views

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 ...
0
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1answer
69 views

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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0answers
316 views

Proxy ARP and ping not working

I am trying to ping the loopback interface on R1. The configuration of the two routers: R1 interface addressing: e0/0 --- 10.1.1.1/24 e0/1 --- 11.1.1.1/24 loopback0 --- 1.1.1.1/32 R2 interface ...
6
votes
1answer
482 views

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.
0
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2answers
103 views

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.
0
votes
1answer
85 views

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 ...
1
vote
2answers
349 views

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/...
1
vote
1answer
168 views

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
0
votes
3answers
836 views

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 ...
0
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2answers
1k views

Difference of tracert and pathping

What is the difference between tracert and pathping command? Thanks
2
votes
1answer
575 views

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 ...
1
vote
1answer
3k views

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?
0
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1answer
142 views

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. ...
2
votes
3answers
874 views

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 ...
0
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2answers
303 views

Ping IP address , 4 Replies

why when ping an IP address we get 4 replies ? thanks
3
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2answers
2k views

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. ...
0
votes
1answer
216 views

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 ...
0
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2answers
112 views

Various ping path

Problem: when i pinged host from CentOS 7 (vm01) other host with different OS (Windows / CentOS - vm02) that i receive error with duplicate packets. When i disabled HSRP and clear arp cache on vm - ...
28
votes
1answer
147k views

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 different results someone says ICMP uses Port 7,...
1
vote
1answer
194 views

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 ...
1
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1answer
493 views

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 ...
0
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1answer
55 views

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? ...
2
votes
1answer
567 views

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 ...
0
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2answers
232 views

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?
0
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2answers
182 views

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, ...
0
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2answers
140 views

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 ...
0
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1answer
93 views

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?
1
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2answers
477 views

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 ...
1
vote
2answers
223 views

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 ...
1
vote
2answers
786 views

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/...
2
votes
2answers
7k views

How to find out TCP/UDP latency of your network?

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 ...
0
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0answers
151 views

hping interval calculation

I am puzzled by hping interval command. -i --interval wait (uX for X microseconds, for example -i u1000) --fast alias for -i u10000 (10 packets for second) --faster alias for -i ...
1
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3answers
73 views

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 ...
1
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2answers
1k views

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....
0
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1answer
90 views

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 ...
0
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1answer
194 views

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
1
vote
2answers
18k views

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 -...
5
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1answer
166 views

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, ...