Opmanager not detecting all router interfaces

Hi,

I've got a Cisco 2821 router with a 16-port Etherswitch module. Asking the router about its SNMP ifIndexes tells me this:

c2821#sh snmp mib ifmib ifindex
GigabitEthernet0/0: Ifindex = 1
Null0: Ifindex = 19
FastEthernet1/0: Ifindex = 3
Port-channel1: Ifindex = 24
Tunnel1: Ifindex = 21
Vlan1: Ifindex = 20
Tunnel2: Ifindex = 23
Vlan2: Ifindex = 25
GigabitEthernet0/1: Ifindex = 2
Vlan3: Ifindex = 26
FastEthernet1/1: Ifindex = 4
FastEthernet1/10: Ifindex = 13
Vlan4: Ifindex = 27
Vlan6: Ifindex = 22
FastEthernet1/2: Ifindex = 5
Vlan7: Ifindex = 28
Vlan8: Ifindex = 29
FastEthernet1/11: Ifindex = 14
Vlan9: Ifindex = 30
FastEthernet1/3: Ifindex = 6
FastEthernet1/4: Ifindex = 7
FastEthernet1/12: Ifindex = 15
FastEthernet1/5: Ifindex = 8
FastEthernet1/13: Ifindex = 16
FastEthernet1/6: Ifindex = 9
FastEthernet1/7: Ifindex = 10
FastEthernet1/14: Ifindex = 17
FastEthernet1/8: Ifindex = 11
FastEthernet1/9: Ifindex = 12
FastEthernet1/15: Ifindex = 18

All the interfaces are there. However, when I discover the device in OpManager, it only shows me interfaces where the ifIndex is 9 or above.

Any idea why?

many thanks,
alec