I have some problems with a very simple DHCP snooping configuration.
I'm using a very simple topology using router on a stick. I use VLAN 10 and VLAN 20.
My Clients can get DHCP from my router when dhcp snooping is not enabled on my switch, but when I enable snooping they can no longer get an IP.
My switch has interface f0/6 and f0/11 as access ports, f0/6 is on vlan 10 and f0/11 is on vlan 20. f0/1 is in trunking mode.
My switch config:
Switch DHCP snooping is enabled DHCP snooping is configured on following VLANs: 1-100 Insertion of option 82 is enabled Option 82 on untrusted port is not allowed Verification of hwaddr field is enabled Interface Trusted Rate limit (pps) ----------------------- ------- ---------------- FastEthernet0/1 yes unlimited
I have full connectivity when DHCP snooping is not enabled so I'm only asking why it doesn't work when snooping is enabled.
My "show run" config on switch:
! ip dhcp relay information trust-all ! ip dhcp snooping vlan 1-100 ip dhcp snooping ! interface FastEthernet0/1 switchport trunk native vlan 99 ip dhcp snooping trust switchport mode trunk ! interface FastEthernet0/6 switchport access vlan 10 switchport mode access ! interface FastEthernet0/11 switchport access vlan 20 switchport mode access ! interface Vlan1 no ip address shutdown ! interface Vlan10 no ip address ip helper-address 192.168.1.1 ! interface Vlan20 no ip address ip helper-address 192.168.2.1 ! interface Vlan99 ip address 192.168.99.99 255.255.255.0 ! end
My "show run" config on router:
ip dhcp relay information trust-all ! ip dhcp excluded-address 192.168.1.1 ip dhcp excluded-address 192.168.2.1 ! ip dhcp pool VLAN10 network 192.168.1.0 255.255.255.0 default-router 192.168.1.1 ip dhcp pool VLAN20 network 192.168.2.0 255.255.255.0 default-router 192.168.2.1 ! interface GigabitEthernet0/0.10 encapsulation dot1Q 10 ip address 192.168.1.1 255.255.255.0 ! interface GigabitEthernet0/0.20 encapsulation dot1Q 20 ip address 192.168.2.1 255.255.255.0