I set up a simple lab and enabled dhcp snooping
I added 'trust' under f0/24 and pc received an ip address, there was a dhcp snooping binding. I removed 'trust', release an ip from the pc and pc did not get an ip. that's great however the switch did NOT report anything on the screen and in the stats I cannot see any dropped dhcp messages? I tried on two Cisco switches...
Switch#sh ip dhc snooping stat det
Packets Processed by DHCP Snooping = 22
Packets Dropped Because
IDB not known = 0
Queue full = 0
Interface is in errdisabled = 0
Rate limit exceeded = 0
Received on untrusted ports = 0
Nonzero giaddr = 0
Source mac not equal to chaddr = 0
No binding entry = 0
Insertion of opt82 fail = 0
Unknown packet = 0
Interface Down = 0
Unknown output interface = 0
Misdirected Packets = 0
Packets with Invalid Size = 0
Packets with Invalid Option = 0
Switch#sh ip dhcp snooping
Switch DHCP snooping is enabled
DHCP snooping is configured on following VLANs:
DHCP snooping is operational on following VLANs:
DHCP snooping is configured on the following L3 Interfaces:
Insertion of option 82 is disabled
circuit-id default format: vlan-mod-port
remote-id: 0019.e8a3.df80 (MAC)
Option 82 on untrusted port is not allowed
Verification of hwaddr field is enabled
Verification of giaddr field is enabled
DHCP snooping trust/rate is configured on the following Interfaces:
Interface Trusted Allow option Rate limit (pps)
----------------------- ------- ------------ ----------------
Switch#sh ip dhc sno sta
Packets Forwarded = 38
Packets Dropped = 0
Packets Dropped From untrusted ports = 0
Windows IP Configuration
An error occurred while renewing interface Local Area Connection : unable to con
tact your DHCP server. Request has timed out.
No other config on the switch, just
ip dhcp snooping vlan 1
ip dhcp snooping
Have I missed sth easy here?
Switch#sh run Building configuration... Current configuration : 1392 bytes ! version 12.2 no service pad service timestamps debug uptime service timestamps log uptime no service password-encryption ! hostname Switch ! ! no aaa new-model system mtu routing 1500 vtp mode transparent ip subnet-zero ! ip dhcp snooping vlan 1 ip dhcp snooping ! ! ! ! ! ! ! ! spanning-tree mode pvst spanning-tree extend system-id ! vlan internal allocation policy ascending ! vlan 2,6,9,74,77 ! vlan 99 name MGMT ! ! ! interface FastEthernet0/1 ! interface FastEthernet0/2 ! interface FastEthernet0/3 ! interface FastEthernet0/4 ! interface FastEthernet0/5 ! interface FastEthernet0/6 ! interface FastEthernet0/7 ! interface FastEthernet0/8 ! interface FastEthernet0/9 ! interface FastEthernet0/10 ! interface FastEthernet0/11 ! interface FastEthernet0/12 ! interface FastEthernet0/13 ! interface FastEthernet0/14 ! interface FastEthernet0/15 ! interface FastEthernet0/16 ! interface FastEthernet0/17 ! interface FastEthernet0/18 ! interface FastEthernet0/19 ! interface FastEthernet0/20 ! interface FastEthernet0/21 ! interface FastEthernet0/22 ! interface FastEthernet0/23 ! interface FastEthernet0/24 ! interface GigabitEthernet0/1 ! interface GigabitEthernet0/2 ! interface Vlan1 ip address dhcp ! ip classless ip http server ip http secure-server ! ! control-plane ! ! line con 0 line vty 0 4 login line vty 5 15 login ! end [b]Switch#sh ip dhcp binding[/b] IP address Client-ID/ Lease expiration Type Hardware address Switch# Switch# Switch#sh ip dh Switch#sh ip dhcp sn Switch#sh ip dhcp snooping stat Packets Forwarded = 147 Packets Dropped = 0 Packets Dropped From untrusted ports = 0 [b]Switch#sh ip dhcp snooping dat[/b] Agent URL : Write delay Timer : 300 seconds Abort Timer : 300 seconds Agent Running : No Delay Timer Expiry : Not Running Abort Timer Expiry : Not Running Last Succeded Time : None Last Failed Time : None Last Failed Reason : No failure recorded. Total Attempts : 0 Startup Failures : 0 Successful Transfers : 0 Failed Transfers : 0 Successful Reads : 0 Failed Reads : 0 Successful Writes : 0 Failed Writes : 0 Media Failures : 0 --------------------------- PC: C:\Users\user>ipconfig /renew Windows IP Configuration An error occurred while renewing interface Local Area Connection : unable to con tact your DHCP server. Request has timed out. An error occurred while releasing interface Loopback Pseudo-Interface 1 : The sy stem cannot find the file specified.
I know this post is very old but I also have the same issue. Were you able to resolve it?
What I have noticed in my setup (Catalyst 3750X) is that I get the same issue in a lab environment setup with the switch logging to it's local log.
If I put the switch into a more complex live setup, logging to Unix Syslog via the logging traps and logging facility global configuration commands, then I do get the events logged to my Syslog server and the statistics are incremented as expected.
It is as if the logging/statistics are bypassed if the switch is only logging locally. I'm not sure if this is a bug or by design.