Possible causes of Ping failure

In normal use, Ping failure is often encountered. There are many reasons for ping failure, such as route settings, or network problems. The following are some reasons:
　
1. too worried. That is, when the network cable is inserted into the switch, you want to ping the gateway, ignoring the convergence time of the Spanning Tree. Of course, newer switches support high-speed spanning trees, or some administrators simply put the user Port
(Access port.
2. Some vroport ports do not agree with the user's ping.
3. Allow question control. No matter how many hops are crossed in the middle, it is normal to have only nodes (including end node points) to filter ICMP. The most common behavior is firewall behavior.

4. Multi-route load balancing. For example, if you successfully ping a remote target host, reply and timed out are staggered. As a result, two routes to the destination CIDR Block exist on the Gateway Router, and the weights of the two routes are equal.
But there is a problem with the query route.
5. Because the delay between devices is too large, icmpecho packets cannot be received within the default time (2 seconds. There are several reasons for latency, for example, line (satellite network latency is 540 milliseconds ),
Hong Kong server lease router processing delay, or unreasonable routing design leads to a roundabout path. Use extended ping to add timed
Outbound time. If Ping is enabled, the route latency is too high.

6. When Nat is introduced, one-way Ping will occur. Nat can conceal the internal address. When the internal IP address is pinged out, the NAT table ing relationship exists. When the external IP address is pinged to the Intranet host
You cannot find the NAT table of the VBR.
7. Specify the extended Ping of the source address. log on to the vro and ping the remote host. When ICMP echorequest is sent from the serial wan interface, the vro will specify an IP address as the source IP address.
It may not be the IP address of this interface or this interface does not have an IP address at all. However, a downstream router may not be able to ping the IP segment. You can use the extended Ping function to specify the source IP address.
8. IP Address allocation is not consecutive. An address planning fault occurs, as if a mine is buried in the network. Overlapping addresses or discontinuous mask division may cause a fault during Ping. For example, in an extreme situation, two hosts, A and B,
After multi-hop connection, a can ping the gateway of B, and the gateway of B is set correctly, but a and B cannot be pinged. After investigation, the second address is also provided on the NIC of B, and the address overlaps with the CIDR block of.