Questions tagged [icmp]

For questions about the Internet Control Message protocol.

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21
votes
7answers
6k views

Why can I traceroute to this IP address, but not ping?

I have an IP address and can traceroute to it, but I can not ping. You see, I can traceroute 43.224.226.50: dele-MBP:~ ll$ traceroute 43.224.226.50 traceroute to 43.224.226.50 (43.224.226.50), 64 ...
0
votes
2answers
52 views

How does packet tracing deterministically work?

If a packet can take any route, how can you iteratively figure out the path from you to a host? From what I can tell, packet tracing works on the basis that packet_i takes a the route: route(...
3
votes
1answer
40 views

How to handle IPv6 Extension Header Options with action = 01

RFC 8200 section 4.2 states that if a node does not recognize an option type, that node must do some action depending on the 2 higher order bits of the option type. When the higher order bits are 01, ...
2
votes
2answers
54 views

How to handle ICMP-in-IPv6 or ICMPv6-in-IPv4?

Since ICMP and ICMPv6 have different IP protocol numbers, it's technically possible for an IPv4 host to receive an ICMPv6 packet or for an IPv6 host to receive an ICMP packet. Is the host's behavior ...
2
votes
1answer
61 views

Virtual IP failover issue with vmware exsi ip based hashing

We are deploying HA database cluster on exsi which based on virtual IP concept for failover. if One node fail reserved VIP will be assigned to another node we have two exsi nodes and two virtual ...
0
votes
1answer
114 views

How to use ICMP to send message

I was trying to send ICMP package with Payload/Message on server_A to server_B(10.1.1.5) as following: ping -p 12345 10.1.1.5. but when I use Tcpdump to capture the ICMP package from server_A, I ...
1
vote
0answers
150 views

Point to Point ICMP Ping Loss between Juniper MX routers

I am facing problem with regard to 1 x 10G link (which is actually configured as an aggregated Ethernet (ae) i.e ae link contains only single 10G link. This ae link is connected between 2 x Juniper ...
1
vote
0answers
190 views

Modifying linux ping icmp payload [closed]

On analyzing ping request and reply from a windows system to Linux. It was observed that the windows ping request payload was "abcdefghijklmnopqrstuvwabcdefghi" with size 32 bytes Could this ...
2
votes
3answers
496 views

Does a router send frames or packets?

Perhaps it's a novice question, but does a router send/receive frames? When I read about this subject, it seems that routers decapsulate the frame on arrival, and encapsulate the packet in a frame in ...
2
votes
2answers
462 views

Which first 8 bytes of the IP datagram are included in ICMP message?

The definition of ICMP message says that it has a type, a code and the first 8 bytes of IP datagram causing error. Question: Which first 8 bytes of IP datagram are included in the ICMP datagram? My ...
8
votes
2answers
1k views

Are ICMP Redirect messages really bad?

Due to potential for MITM attack, ICMP redirect messages should be blocked. However, the original purpose of the ICMP redirect message is to inform the host of a better router (or gateway). Then, is ...
1
vote
3answers
77 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
90 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 ...
5
votes
2answers
359 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....
9
votes
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?
1
vote
2answers
107 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?
1
vote
1answer
173 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 ...
2
votes
6answers
5k 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
votes
1answer
606 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 ...
2
votes
3answers
2k 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
44 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
votes
2answers
179 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
vote
3answers
82 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 ...
1
vote
3answers
112 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 ...
1
vote
1answer
111 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 ...
6
votes
1answer
873 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
votes
2answers
321 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
136 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
508 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
265 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
1
vote
3answers
2k 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 ...
1
vote
2answers
3k views

Difference of tracert and pathping

What is the difference between tracert and pathping command? Thanks
2
votes
1answer
1k 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
6k 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
votes
1answer
212 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
1k 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 ...
1
vote
2answers
473 views

Ping IP address , 4 Replies

why when ping an IP address we get 4 replies ? thanks
3
votes
2answers
4k 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
288 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
votes
2answers
115 views

Various ping path [closed]

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 - ...
44
votes
4answers
234k 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
269 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
vote
1answer
700 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 ...
1
vote
1answer
62 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
751 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 ...
1
vote
2answers
318 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?
1
vote
2answers
197 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, ...
1
vote
2answers
174 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 ...
1
vote
1answer
144 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
vote
2answers
548 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 ...