Description

Questions about DHCP lease configuration and relay bindings are covered in this article.

 

Solution

1. When delete/modify the existing dhcp relay configuration , will there be any impact to the already leased endpoints? 

Answer: If you execute the command delete forwarding-options dhcp-relay, it effectively disables the DHCP relay functionality on the device and the already leased endpoints will continue to operate normally until their leases expire. The impact depends on the lease duration set in your DHCP configuration. If the lease duration is short (e.g., a few minutes), the impact will be immediate. The leased IP addresses will expire quickly, and clients will need to renew their leases. If the lease duration is long (e.g., several days), the impact will be delayed until the existing leases expire naturally. Hence, it is recommended to do the changes in a maintenance window.

2. What is the purpose of the following command: 
set forwarding-options dhcp-relay active-server-group allow-server-change
Answer: To enable ACK forwarding from any server in the active server group, we can use the below command. 
[edit forwarding-options dhcp-relay active-server-group]
user@host# set allow-server-change

3. When the command is issued “delete forwarding-options dhcp-relay” at this stage the DHCP relay binding table is cleared. Does this cause the DHCP server to send a FORCERENEW packet or anything like this?

Answer: It is platform specific feature and depends on the DHCP server platform model. Verified the details regarding FORCERENEW packet and we would like to inform you that Dynamic reconfiguration for DHCPv4 is available through a partial implementation of RFC 3203, DHCP Reconfigure Extension for DHCPv4. It enables the DHCPv4 local server to send a message to the client to force reconfiguration.
 
DHCP relay and DHCP relay proxy do not participate in the client reconfiguration or react to forcerenew messages other than to forward them to the client. Only the exchange of forcerenew, renew, and NAK messages is supported from RFC 3202.
 

Modification History

2024-04-16: Article validated.
2024-04-12 : Article Created

Related Information

Please refer below article for more details.

https://www.juniper.net/documentation/us/en/software/junos/dhcp/topics/topic-map/dhcp-relay-agent-common-configuration-applying.html

Please refer below articles for more details about FORCERENEW packet and Dynamic reconfiguration of extended DHCP local server clients/Dynamic reconfiguration of extended DHCPv6 local server clients.
 
https://www.juniper.net/documentation/us/en/software/junos/subscriber-mgmt-sessions/topics/topic-map/dhcp-dynamic-reconfiguration-clients.html

https://apps.juniper.net/feature-explorer/parent-feature-info.html?pFKey=1328&pFName=Dynamic%20Host%20Configuration%20Protocol%20(DHCP)