What is the reason why the IP address cannot be pinged?

The reasons why the ip address cannot be pinged: 1. The convergence time of the spanning tree is ignored; 2. Some router ports do not allow users to ping; 3. Multi-route load balancing situations; 4. The network is due to differences between devices. The delay is too large; 5. When NAT is introduced, it will cause one-way ping.

#The operating environment of this article: Windows 7 system, Dell G3 computer.

The reason why the ip address cannot be pinged:

1. Too impatient. That is, trying to ping the gateway as soon as the network cable is plugged into the switch, ignoring the spanning tree convergence time. Of course, newer switches support high-speed spanning tree, or some administrators simply turn off the spanning tree protocol of user port

(access port), and the problem is solved.

2. Some router ports do not allow users to Ping.

3. Access control. No matter how many hops are spanned in the middle, as long as there is a node (including end nodes) filtering ICMP, it is normal for Ping to fail. The most common is the behavior of firewalls.

4. Multi-route load balancing scenarios. For example, when pinging the remote destination host, successful replies and timed outs appear alternately. It turns out that there are two routes to the destination network segment on the gateway router. The weights of the two routes are equal, but there is a problem with one route.

5. Because the network delay between devices is too large, the ICM Echo message cannot be received within the default time (2 seconds). There are several reasons for the delay, such as lines (satellite network delay up and down is 540 milliseconds), Hong Kong server rental router processing delay, or unreasonable routing design causing roundabout paths. Use extended ping and add timedout time. If the ping succeeds, the problem is that the routing delay is too large.

6. When NAT is introduced, one-way ping will occur. NAT can hide the internal address. When pinging from the inside to the outside, the ping can be successful because the mapping relationship in the NAT table exists. When pinging the internal network host from the outside, there is no way to find the NAT entry of the border router.

7. Extension Ping to specify the source address. Log in to the router and ping the remote host. When the ICMP echorequest is sent from the serial WAN interface, the router will specify an IP address as the source IP. This IP The address

may not be the IP of this interface or the interface may not have an IP address at all. A certain downstream router may not have a route to this IP network segment, causing the ping to fail. You can use extended Ping to specify the source IP address.

8. IP address allocation is not continuous. Failure in address planning is like laying mines in the network. Overlapping addresses or discontinuous mask division may cause failures during ping. For example, in an extreme case, two hosts A and B are connected through multiple hops. A can ping B's gateway, and B's gateway is set correctly, but A and B cannot ping. After investigation, it was found that there is a second address on B's network card, and this address overlaps with the network segment where A is located.

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