topic RE: S4 DHCP Bindings in ExtremeSwitching (EOS)

S4 DHCP Bindings

Philipp_Tittman — Fri, 19 Jun 2015 17:10:00 GMT

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

RE: S4 DHCP Bindings

Careno__Ryan — Fri, 19 Jun 2015 20:41:00 GMT

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 "

Regards,
Ryan Careno

RE: S4 DHCP Bindings

Philipp_Tittman — Mon, 22 Jun 2015 13:27:00 GMT

Hi Ryan,

great! Thank you very much

Regards,
Philipp

RE: S4 DHCP Bindings

Careno__Ryan — Mon, 22 Jun 2015 22:24:00 GMT

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