S4 DHCP Bindings

  • 0
  • 1
  • Question
  • Updated 3 years ago
  • Answered
  • (Edited)
Hi Guys, 

on a S4 Switch i have a dhcp pool enabled on a vlan. when i do "show ip dhcp binding" there are a lot of addresses with status "blocked" without any MACs associated. Does anybody know what that exactly means or when did this status appears?

Thanks in advance
Phil
Photo of Philipp Tittmann

Philipp Tittmann

  • 774 Points 500 badge 2x thumb

Posted 3 years ago

  • 0
  • 1
Photo of Careno, Ryan

Careno, Ryan, Employee

  • 1,092 Points 1k badge 2x thumb
Hello Phil,

Please see the following GTAC Knowledge article I just published:

https://gtacknowledge.extremenetworks.com/articles/Q_A/Why-does-S-N-K-Series-show-DHCP-Binding-state-blocked-for-Client-IP-Address/

The router sends a ping to an IP address before offering an IP address to a client.  If the IP address gets an ICMP response, we see there's someone already on the network with that IP address and mark it as "blocked" so we do not hand out duplicate addresses.

Once you find the client that already has the IP address in the DHCP scope (possibly set statically), you should be able to clear up the blocked binding with command "clear ip dhcp binding <IP_ADDR>"

Regards,
Ryan Careno
(Edited)
Photo of Philipp Tittmann

Philipp Tittmann

  • 774 Points 500 badge 2x thumb
Hi Ryan, 

great! Thank you very much

Regards,
Philipp
Photo of Careno, Ryan

Careno, Ryan, Employee

  • 1,092 Points 1k badge 2x thumb