Showing results for 
Search instead for 
Did you mean: 

Problem with DHCP Snooping and Option 82 (Resolve)

New Contributor III
Hi team!
I test DHCP Snooping on switches ICX7250 and ICX7150 (hw ver. 8.0.9). DHCP-Server was Cisco switch.

I configured DHCP Snooping according to manual:
    enable acl-per-port-per-vlan
    ip dhcp snooping vlan 100
   interface lag 1
    dhcp snooping trust

Clients on untrusted ports didn't get ip addresses from DHCP-Server.
All because DHCP option 82 is enabled on ICX by default and switch addes it to requests. But Cisco switch doesn't understand this requests.

Debug log from ICX7250:
    DHCP: snooping on for vlan 100, port 1/1/1
    DHCP: rcv on port 1/1/1, intercept DHCP pkt, Request
    DHCP: snooping on port 1/1/1, smac 10e7.c6e5.4d01, type 3, VRF default-vrf>10e7.c6e5.4d01
    DHCP Option82: Adding option 82
    DHCP Option82: 20 bytes added.
    DHCP Option82: Adding option 82

Debug log from Cisco switch (DHCP-server):
    DHCPD: Reload workspace interface Vlan100 tableid 0.
    DHCPD: tableid for on Vlan100 is 0
    DHCPD: client's VPN is .
    DHCPD: inconsistent relay information.
    DHCPD: relay information option exists, but giaddr is zero.

I disabled DHCP option 82 and it's started work normally:
    (config)#ip dhcp snooping relay information disable
        or on interface
    (config-if-e1000-1/1/1)#no ip dhcp snooping relay information

Maybe anybody knows another way to resolve this problem.

New Contributor II
option 82 is known to cause issues and it is recommended to disable it.  Even on my 99% cisco network, the "no ip dhcp snooping information option" is a part of our standard configuration.

New Contributor
Can you try ICX with ip helper-address configuration under a VE i.e. making it a relay agent and try inter-op with CISCO (DHCP Server)

By Default Cisco IOS devices reject packets with zero “giaddr” and by default Cisco Catalyst switches use “giaddr” of zero when configured for DHCP snooping