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