CCIE EXAM DUMPS Three minutes to learn the practical application of ICMP protocol
ICMP is the Internet Control Message Protocol . It is a sub-protocol of the TCP/IP protocol suite for passing control messages between IP hosts and routers.Control message refers to the network itself, such as the network is unreachable, the host is reachable, and the route is available.Although these control messages do not transmit user data, they play an important role in the transmission of user data.
ICMP protocol format:
From a technical point of view, ICMP is a "error detection and reward mechanism".ccie exam dumps.Its purpose is to enable us to detect the connection status of the network and ensure the accuracy of the connection. Its functions are mainly:
- Detect if the remote host exists.
- Establish and maintain routing data.
- Redirect the data transfer path (ICMP redirection).
One application of ICMP is Ping. Ping is a common tool for detecting network connectivity and is able to collect other relevant information.You can specify the same parameters in the ping command, such as the length of the ICMP packet, the number of ICMP packets sent, and the timeout period for waiting for a response. Ccie exam dumps.The device constructs and sends an ICMP packet based on the configured parameters.
When a ping connection is made to a remote host on a computer, the return messages that may be received are:
- Connection established successfully
Reply from 192.168.1.1:bytes=32 time<1ms TTL=128
- Destination host unreachable
- Request timed out.
- Unknown host abc.
Common parameter configuration:
-t: Always ping until manually closed (^C)
-a: display the host name of the other party
-l: Bytes, send a ping packet of the specified size.
Another typical application for ICMP is Tracert. Tracert tracks the forwarding path of packets hop by hop based on the TTL value in the packet header.The Tracert diagnostic determines the route taken to the destination by sending an Internet Control Message Protocol (ICMP) response packet with a different IP Time to Live (TTL) value to the destination.ccie exam dumps.Each router on the path is required to decrement at least the TTL on the packet before forwarding the packet.When the TTL on the packet is reduced to 0, the router should send a message "ICMP has timed out" back to the source system.
Tracert first sends a response packet with a TTL of 1, and increments the TTL by 1 in each subsequent transmission until the target response or TTL reaches a maximum value to determine the route.ccie exam dumps.The route is determined by checking the "ICMP has timed out" message sent back by the intermediate router.Tracert is an effective means to detect network packet loss and delay. It can also help administrators discover routing loops in the network.
Common parameter configuration:
- -d: Do not resolve the address to a host name.
- -h: The maximum number of hops for the search target.
- -j: Loose original route along with the host list (for IPv4 only).
- -w: Wait for the timeout for each reply.
- -R: Tracks the round trip path (for IPv6 only).
- -S: Source address to use (IPv6 only).
- -4: Forced use of IPv4.
- -6: Mandatory use of IPv6.
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