Questions tagged [icmp]

For questions about the Internet Control Message protocol.

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15 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 ...
63
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5answers
376k 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 results someone says ICMP uses Port 7, someone ...
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0answers
20 views

ECT Marked ICMP Responses

For ongoing research I'm conducting, I'm measuring the modification of ECT fields of the IPv[46] header. To do this I'm relying on ICMP quotations to inspect what packets 'look like' as they traverse ...
7
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5answers
2k views

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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2answers
22 views

Traceroute to any private IP works? [closed]

I am setting up an OpenVPN p2p between two locations. One in Canada and the other in Barbados. From the router in Barbados, when I do a traceroute to let's say, 10.230.50.1, I can see it going through ...
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2answers
179 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 ...
0
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1answer
36 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 ...
2
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2answers
1k views

NAT Translation Table Port Number

I had a practice question about a NAT-enabled router with outside address 24.34.112.235 and inside network 192.168.1/24 and three inside hosts .1, .2 and .3. The three hosts all open two connections ...
0
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2answers
278 views

Why does NAT keep track of each packet not just connections?

I have tried packet tracer and actual cisco routers and I find this weird: NAT uses different source ports, usually incrementally, for consecutive packets from the same connection. Why is that? ...
2
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3answers
119 views

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)?
2
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2answers
170 views

Traceroute probes

In traceroute, when a * is recieved, it could mean the router didn't reply due to various reasons- either the router is busy processing other packets or ICMP is blocked. I think few ISPs configure ...
6
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2answers
5k views

What would happen to Ping if two PCs have same IP address with same Subnet Mask on same network?

If there are two PCs with same IP address on a LAN, what would happen if I ping that IP address from another PC on the same network and why?
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2answers
2k views

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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2answers
47 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 ...
2
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1answer
79 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 ...
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2answers
51 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?
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2answers
42 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 ...
0
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1answer
36 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 ...
-1
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3answers
492 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 ...
3
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2answers
143 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 ...
6
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2answers
991 views

IP Traceroute RFC 1393

Is RFC 1393 implemented by real routers in practice? Are there any tools that generate traceroutes using it?
2
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6answers
79k views

How Can I use “ping command” with source?

I can not use ping 'target' source 'interface' ping 192.168.0.2 source lo0 % Invalid input detected at '^' marker. It's possible if I use "ping" R2#ping Protocol [ip]: ip Target IP address: 192....
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2answers
35 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.
3
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4answers
54k views

pinging broadcast address

Iam using linux.I read somewhere in the internet that pinging the 255.255.255.255 will ping everyone in the network segment. And it will return every ip addresses in that subnet. but when i tried ...
24
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7answers
12k 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 ...
0
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1answer
52 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 ...
0
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2answers
80 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 ...
0
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2answers
746 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 ...
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0answers
97 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 ...
1
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4answers
147 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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3answers
148 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 ...
2
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3answers
2k views

Which first eight 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 eight bytes of IP datagram are included in the ICMP datagram? ...
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4answers
4k 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-...
5
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2answers
57k 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 -...
0
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2answers
203 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 ...
1
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2answers
67 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(...
4
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2answers
72k views

dont fragment bit PING TOOL

Actually my machine wwan0 MTU is 1500 ashokkrishna@ashokkrishna-Lenovo-B560:~$ ping -s 1490 example.com PING example.com (93.184.216.119) 1490(1518) bytes of data. 1498 bytes from 93.184.216.119: ...
3
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1answer
49 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
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2answers
163 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
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1answer
839 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
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1answer
1k 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 ...
11
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4answers
41k views

Interpreting TTL in ping results

I work for a VoIP service provider and I am working an issue with a customer who has a cable internet connection that's throwing me for a loop. He has a single block, which we'll pretend is 70.141.15....
2
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0answers
739 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
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0answers
2k 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 ...
4
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3answers
2k 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 ...
1
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3answers
105 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. ...
1
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1answer
979 views

ICMP Redirect , static routing

I am learning about ICMP Redirect and I struggle with understanding it. For example, I have a network like this : I want to communicate from PC0 to PC1 which are on different subnet and at the ...
1
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1answer
214 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 ...
5
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2answers
4k views

Calculating checksum for ICMPv6

Referring http://www.faqs.org/rfcs/rfc1071.html, I try to deduce the c code for calculating the checksum for ICMPv6. But check with the checksum parse by wireshark, I find that the answer got from my ...
1
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1answer
1k 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 ...