Why cannot get an IP address when there are many users?

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Zyxel_James
Zyxel_James Posts: 616  Zyxel Employee
First Anniversary 10 Comments Friend Collector First Answer

Question: Why I cannot get an IP address successfully even though I perform IP renewal multiple times?

Answer: It could be DHCP process time out due to so many ARP checks being performed. To get an IP address, the client will send ARP check to ensure if the IP address has already been used. So when more DHCP clients request an IP address, the device will perform more ARP checks, which may cause DHCP process time out.

You can disable the ARP check by CLI command:
Router# configure terminal
Router(config)# no ip dhcp arp_check
Router(config)# write

After the operation, the device won't send the ARP checks anymore.
Please note that when ARP check is disabled, all of the clients must use DHCP to get the IP address. Static IP host won't be able to access the internet even if it has already received an IP address.