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Questions tagged [icmp]

For questions about the Internet Control Message protocol.

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Missing ICMP identifier equivalent in ARP protocol and desired arping behavior

Running simultaneously more arping on the same interface and the destination IP address all clients get the responses due missing ICMP identifier equivalent. First, am I correct that there is no ICMP ...
pevik's user avatar
  • 147
-1 votes
1 answer
64 views

Why MLS2 Doesn't Get ICMP Packet To Where It Should?

This is a Packet Tracer lab from Kieth Barker's website with minor modifications. It is intended to exhibit how can we get to the network 10.10.0.0/24 access to the Web Server 23.1.2.2/24 Using NAT. ...
Shadi's user avatar
  • 285
0 votes
1 answer
80 views

In wireshark, why following a TCP or UDP stream does not remove ICMP packets?

In Wireshark, when I follow a TCP or UDP stream using right click -> Follow -> UDP Stream, if there are some ICMP packets from same endpoints, wireshark will keep them in the stream. Why? Since ...
Sourav Kannantha B's user avatar
0 votes
2 answers
82 views

Do destination hosts decrement the TTL?

I was trying to understand more about traceroute when I stumbled upon this site and I have a question about this diagram: As you can see in the diagram, the destination host S1 receives a packet ...
Noob_Guy's user avatar
  • 491
0 votes
1 answer
106 views

In a trace route, do routers that do not respond still forward the packets?

In traceroute, The sender expects a reply within a specified number of seconds. If a packet is not acknowledged within the expected interval, an asterisk is displayed. Pasting here the example trace ...
Noob_Guy's user avatar
  • 491
1 vote
1 answer
80 views

The TTL and packet drop [duplicate]

I would just like to verify one thing. When a router receives a packet with a TTL of 1, the router can still process and accept it if its destined for itself, correct? Because for example, eBGP ...
Mitrixsen's user avatar
  • 803
0 votes
1 answer
73 views

BGP configuration multi-hop ping not working

I'm learning bgp and studying on a simple lab I'm unable to ping a loop0 two hops away while the loop0 on the nex-hop router is reachable Topology is simple R3-R1-R2, from R2 i'm able to ping loop0 on ...
Matteo's user avatar
  • 5
0 votes
1 answer
1k views

Why am I not capturing any ICMP packets on wireshark?

I am doing a lab where we are meant to ping an address and use wireshark to capture ICMP packets when we ping that address. WHen I run the wireshark capture with the ICMP filter on and ping my address,...
Garrett LaCoste's user avatar
0 votes
1 answer
82 views

Change source and destination adresses from a valid captured ping to create a valid ping with different source and destination

I want to create traffic in my network, especially I want to send a repetitive ping to the device with the IP 192.168.3.146 from my traffic generator (IP 192.168.3.100) (see scematic) For the creation ...
sellerBasti's user avatar
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0 answers
52 views

Cannot ping interface although in same subnet? Why? Debug ip packet gives encapsulation error

I have the following setup: From Laptop Mgmt2 (bottom right) I want to ping Se/0/0/0 on R1. I can only ping S0/0/0 on ISP router, which is in the same subnet. If I enable debug ip packet on isp router ...
Rubus's user avatar
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1 answer
134 views

ICMP error message's data for IP datagram with < 64 bits payload?

RFC792: The internet header plus the first 64 bits of the original datagram's data. This data is used by the host to match the message to the appropriate process. If a higher level protocol uses ...
YouJiacheng's user avatar
0 votes
2 answers
451 views

IP packet expired by TTL generate an ICMP response in any case?

Acording to Wikipedia IPv4 article for TTL header field: An eight-bit time to live field limits a datagram's lifetime to prevent network failure in the event of a routing loop. It is specified in ...
rfmoz's user avatar
  • 103
3 votes
2 answers
4k views

Is DHCP in the application layer or the network layer?

Tanenbaum's Computer Networks says: 5.6 THE NETWORK LAYER IN THE INTERNET ... 5.6.4 Internet Control Protocols In addition to IP, which is used for data transfer, the Internet has several companion ...
Tim's user avatar
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1 vote
1 answer
466 views

ICMP codes in response to ICMP traffic, not UDP/TCP

I am trying to wrap my head around a concept and I am having some trouble. If I ping 8.8.8.8, 10.8.1.1 replies to me "Destination port unreachable". Ping uses ICMP, so it does not have a '...
user83344's user avatar
0 votes
2 answers
120 views

If ICMP packet is lost then another ICMP could be generated?

Suppose there are two routers between Source and destination R1, R2 respectively. Suppose source sending packet to R1 and then R1 send to R2, but R2's buffer is full and discarded the packet and ...
S. M.'s user avatar
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1 answer
38 views

Actually ICMP message makes layer3 reliable?

We know that ICMP is connectionless because it does not require hosts to handshake before establishing a connection. But when packets gets dropped in between route then respective router informs the ...
S. M.'s user avatar
  • 398
3 votes
1 answer
65 views

Should Bit Errors Cause Loss Proportional To PDU Size?

Should I expect random (or even regularly-occurring) bit errors to cause corrupted/dropped PDUs (packets) proportionate to the PDU size ? Troubleshooting high (0.01% to 0.1%) packet loss over a short (...
robut's user avatar
  • 243
0 votes
2 answers
1k views

What does a router do with a packet if it can't find the destination IP address in its routing table?

If a router receives an ARP request in which the destination hardware address is a broadcast address, and if the destination IP address is an address that the router cannot find in its routing table. ...
Avenger.1995's user avatar
0 votes
2 answers
515 views

How is traceroute Time to Live decremented?

By default, for Traceroute utility, the "time to live" value will be decremented by 1 each time packet passes through a router. However, is the "time to live" value also ...
Student95's user avatar
1 vote
1 answer
147 views

Is ICMP protocol widely used in real world?

Is the ICMP protocol generally used in real world networking configurations ? If yes, what are some real world examples that make use of this protocol. In addition, I see that the ICMP echo requests ...
Floji's user avatar
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1 vote
1 answer
3k views

Possible causes of ICMP Destination unreachble - Port unreachable

Are there any other causes, apart from the specific port to be reached being closed, that can lead to an ICMP Destination unreachable - Port unreachable message? What are possible reasons for this ...
user avatar
2 votes
2 answers
2k views

How exactly does Path-MTU Blackhole Detection work?

I'm currently trying to understand how the Path-MTU Blackhole Detection really works. From what I understand: You send rather big packets, starting at like 1460 Bytes (TCP example) and wait for ...
Gereon99's user avatar
  • 123
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0 answers
121 views

What is making switch CPU so busy that it's unable to respond with ICMP errors?

According to How to prioritize ICMP time exceeded packets my switch is dropping ICMP error replies because the CPU is apparently too busy. It is a PowerConnect 7048 and it dropping anywhere between 5% ...
user3280964's user avatar
1 vote
1 answer
719 views

How to prioritize ICMP time exceeded packets

According to why ICMP Time Exceeded packet takes longer ICMP Echo Reply, it is normal for ICMP time exceeded be treated as low priority and slowed down or even discarded. I'm observing this problem ...
user3280964's user avatar
0 votes
1 answer
1k views

Static Routing - host to host ping does not work (MikroTik)? [closed]

I'm trying to do static routing using actual devices. Below is my setup: The left router is a MikroTik RouterBoard hAP lite. The right router is a MikroTik RouterBoard hAP ac. I want to ping from ...
Noob_Guy's user avatar
  • 491
1 vote
2 answers
457 views

why ICMP Time Exceeded packet takes longer ICMP Echo Reply

I've noticed that when I use tracert a certain router(hop) always takes about 200ms to reply back, the rest reply's in 50ms, after digging into it with wireshark I've noticed that tracert uses normal ...
Naeem John's user avatar
2 votes
1 answer
1k views

IPv4 and UDP/TCP packets inside of ICMP packet?

A week ago, after opening wireshark, i was surprised by seing a storm of ICMP packets from different IP addresses. While deep analysing of thoses packets, i noticed that those ICMP packets contains ...
Yazid's user avatar
  • 23
1 vote
2 answers
92 views

ICMP distinguish error messages

Can a Internet Control Message Protocol when an error is sent can it tell which datagram that made the error?
Jonte YH's user avatar
  • 147
0 votes
1 answer
79 views

When I send the ICMP packet with 4000B, but the IPv4 segment calculated 4008B

When I send the ICMP packet with data size as 4000B for testing the IP fragment. ping 192.168.2.1 -c1 -s4000 and the Wireshark captured it, Whether is is because of ICMP header? but we know ICMP ...
244boy's user avatar
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0 votes
2 answers
3k views

What's the Destination unreachable ICMP packet(ICMP payload the UDP) usage? [closed]

In my Mac(192.168.2.228), it will send ICMP packet to my house's router (192.168.2.1). with the info Destination unreachable (Port unreachable) and in the Wireshark packet detail panel, there ...
244boy's user avatar
  • 1,777
-1 votes
3 answers
6k views

Confusion about TTL when pinging

TTL value of a packet is supposed to decrease 1 at each router from 255 down to zero as follows: But when I ping to 8.8.8.8 the TTL starts at 253 and doesn't change: How can this be explained? Why ...
pnatk's user avatar
  • 101
2 votes
2 answers
1k views

Confusion about MTU

I am studying about IP fragmentation and MTU. What I know is MTU is the property of Physical medium, as in the amount of data it can process without having to fragment the data. The default MTU on ...
Techievent.in's user avatar
0 votes
2 answers
247 views

How to check cable without ping?

Is there any way to check if a network link is physically working, without using ping? Recently bought a Power-Line-Communication device, and I wanted to test if it works. Before pinging the machines ...
ymudyruc's user avatar
0 votes
2 answers
84 views

ICMP is a protocol working in the Network Layer. Why does it send few fields of the transport layer while reporting an error?

I was confused if ICMP is a network layer protocol why does it send transport layer fields in its error reporting messages.
Karan's user avatar
  • 3
0 votes
1 answer
293 views

Broadcast ICMP and gratuitous ARP

When sending an ICMP broadcast, all nodes can respond. is it the case of the sender too? If it's the case then: Is it specified somewhere that the sender should respond with gratuitous ARP when the ...
Lkaf Temravet's user avatar
0 votes
2 answers
5k views

Permit ping and traceroute and deny all other services using an ACL

my topology is shown below: I would like the networks that are connected to Hermes-Router to be accessible from all the other stations only when I use ping and traceroute. I tried to do this using an ...
Giannis Matsarokis's user avatar
1 vote
0 answers
741 views

ICMP No Reply Found Issue [closed]

Currently working on a Go based NAT router and when translating ICMP traffic and am seeing some interesting behavior. The clients request is forwarded to the server, the server keeps track of the ...
toothflower's user avatar
0 votes
2 answers
129 views

How computer "knows" how and what to respond to particulary ICMP messages

How a computer "knows" what to respond to particular ICMP messages? As is known there are various ICMP messages that differ by type and / or code. For example ICMP type 0 is "echo reply", type 13 /14 ...
Antares's user avatar
1 vote
3 answers
912 views

Estimate latency between two IP addresses

I would like to estimate what is the latency in sending a packet between two IP addresses. Let's assume that I have two IP addresses: ip1 and ip2. I can easily ping both ip1 and ip2, and the ping ...
Ziva's user avatar
  • 111
1 vote
4 answers
25k views

Why ICMP Destination Port Unreachable error messeage is generated for unreliable UDP packets?

My doubt is why an icmp destination port unreachable error message generated for udp. Why we can't simply discard the udp packet if the destination port is not reachable by saying udp is connection-...
Amal's user avatar
  • 13
0 votes
2 answers
1k views

While sniffing with Wireshark, i get lot of ICMP packets in my loop back interface with the word "CKAAAA.." in it, why is this happening? [closed]

So i have a parrot VM, and i tried to use wireshark on the lo interface of it just for fun, now I'm seeing loads of ICMP packets, which seems to be Netbios inside(not sure why is Wireshark naming the ...
Mery Ted's user avatar
  • 101
28 votes
7 answers
25k 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 43.24.226.50: dele-MBP:~ ll$ traceroute 43.24.226.50 traceroute to 43.24.226.50 (43.24.226.50), 64 hops ...
244boy's user avatar
  • 1,777
1 vote
2 answers
90 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(...
Tobiq's user avatar
  • 213
3 votes
1 answer
62 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, ...
ghanan94's user avatar
3 votes
2 answers
571 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 ...
joshlf's user avatar
  • 327
2 votes
1 answer
2k 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 ...
gripenfighter's user avatar
1 vote
1 answer
4k 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 ...
Jack's user avatar
  • 317
2 votes
0 answers
2k 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 ...
Nabeel's user avatar
  • 1,120
1 vote
0 answers
4k 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 ...
PDHide's user avatar
  • 227
5 votes
3 answers
5k 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 ...
Smbbo's user avatar
  • 51