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The ICMP header starts after the IPv4 header and is identified by its protocol number, 1. [6] All ICMP packets have an eight-byte header and variable-sized data section. The first four bytes of the header have fixed format, while the last four bytes depend on the type and code of the ICMP packet.
When the UDP mode is used, MTR relies on ICMP port unreachable packets (type 3, code 3) when the destination is reached. MTR also supports IPv6 and works in a similar manner but instead relies on ICMPv6 messages. The tool is often used for network troubleshooting.
ICMP tunneling works by injecting arbitrary data into an echo packet sent to a remote computer. The remote computer replies in the same manner, injecting an answer into another ICMP packet and sending it back. The client performs all communication using ICMP echo request packets, while the proxy uses echo reply packets.
On various routers, this TCP or UDP port 7 for the Echo Protocol for relaying ICMP datagrams (or port 9 for the Discard Protocol) is also configured by default as a proxy to relay Wake-on-LAN (WOL) magic packets from the Internet to hosts on the local network in order to wake them up remotely (these hosts must also have their network adapter ...
Traceroute can help identify incorrect routing table definitions or firewalls that may be blocking ICMP traffic, or high port UDP in Unix ping, to a site. [clarify] A correct traceroute response does not guarantee connectivity for applications as a firewall may permit ICMP packets but not permit packets of other protocols.
The Point-to-Point Protocol over Ethernet (PPPoE) is a network protocol for encapsulating Point-to-Point Protocol (PPP) frames inside Ethernet frames. It appeared in 1999, in the context of the boom of DSL as the solution for tunneling packets over the DSL connection to the ISP's IP network, and from there to the rest of the Internet.
In computer networking, the ICMP Internet Router Discovery Protocol (IRDP), also called the Internet Router Discovery Protocol, [1] is a protocol for computer hosts to discover the presence and location of routers on their IPv4 local area network. Router discovery is useful for accessing computer systems on other nonlocal area networks. [2]
A stateful firewall keeps track of the state of network connections, such as TCP streams, UDP datagrams, and ICMP messages, and can apply labels such as LISTEN, ESTABLISHED, or CLOSING. [2] State table entries are created for TCP streams or UDP datagrams that are allowed to communicate through the firewall in accordance with the configured ...