also gives us a chance to view the route from the host to the target host. This is because, when the ICMP ping request datagram passes through a vro, The vro will put its own IP address in the report. The target host will copy the IP address list to the host in response to the ICMP packet. However, in any case, the list of routes that the IP header can record is very limited. To observe routing, we still n
echo and ICMP echo reply packets to detect the presence of the host, so the process of pinging is simple: sending ICMP echo packets----> receiving ICMP Echo reply packets)Ping gives us a chance to see the host's route to the destination host. This is because the ping request datagram for ICMP is reported by the router
, such as sf.net, if you are interested. Then you can see packet loss, the program runs for a longer time.Ping also gives us a chance to view the route from the host to the target host. This is because, when the ICMP ping request datagram passes through a vro, The vro will put its own IP address in the report. The target host will copy the IP address list to the host in response to the ICMP packet. However,
from the host to the target host. This is because, when the ICMP ping request datagram passes through a vro, The vro will put its own ip address in the report. The target host will copy the ip address list to the host in response to the icmp packet. However, in any case, the list of routes that the ip header can record is very limited. To observe routing, we still need to use a better tool, that is,
us a chance to view the route from the host to the target host. This is because, when the ICMP ping request datagram passes through a vro, The vro will put its own IP address in the report. The target host will copy the IP address list to the host in response to the ICMP packet. However, in any case, the list of routes that the IP header can record is very limited. To observe routing, we still need to use
reported by the router to put its own IP in the datagram every time it passes through a router. The destination host copies the IP list back to the host in response to the ICMP packet. However, in any case, the list of routes that the IP header can record is very limited. If we want to observe the route, we still need to use a better tool, that is, Traceroute (the name under Windows is called tracert).Appl
returns an ICMP inaccessibility packet, and sets the combination of the type and code in the packet to port inaccessibility. The Traceroute program generates ICMP error packets by using port unavailability.
In addition, in most cases, an ICMP error message is generated when an error occurs when an IP datagram is trans
the original IP header and data portion that caused the ICMP error message to be generated (such as UDP or TCP for the transport layer, which contains the port number). Here the original IP header of the Protocol field and the first 8 bytes of the port number, you can determine which protocol and which user process.In addition to the ICMP error message above, the ICMP
tcp-m tcp--dport 22-j DROP-A output-m conntrack--ctstate new-j ACCEPTCOMMIT# completed on Fri Dec 19 17:01:18 2014It has been noted that:-A input-j DROP--------------------------------------->ping is output;traceroute when each routing node returns the packet;The rule-a output-m conntrack--ctstate new-j Accept is the TCP protocol by default, whereas the Ping/traceroute uses the
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