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DHCP Snooping Dropped Packets

FuadG
Level 1
Level 1

Hello everyone!

We have configured DHCP snooping on one of our switches. All works fine, clients are able to get IP addresses, I can see the bindings table. However, what bothers me, is that there are lots of dropped packets in statistics

Packets Forwarded = 10936
Packets Dropped = 5358
Packets Dropped From untrusted ports = 0

When I check debug output, this is what I get

Sep 28 13:35:30: DHCPSNOOP(hlfm_set_if_input): Setting if_input to Gi0/2 for pak. Was not set
Sep 28 13:35:30: DHCPSNOOP(hlfm_set_if_input): Clearing if_input for pak. Was Gi0/2
Sep 28 13:35:30: DHCPSNOOP(hlfm_set_if_input): Setting if_input to Gi0/2 for pak. Was not set
Sep 28 13:35:30: DHCP_SNOOPING: received new DHCP packet from input interface (GigabitEthernet0/2)
Sep 28 13:35:30: DHCP_SNOOPING: process new DHCP packet, message type: DHCPINFORM, input interface: Gi0/2, MAC da: ffff.ffff.ffff, MAC sa: 80c1.6efa.bddb, IP da: 255.255.255.255, IP sa: 192.168.146.242, DHCP ciaddr: 192.168.146.242, DHCP yiaddr: 0.0.0.0, DHCP siaddr: 0.0.0.0, DHCP giaddr: 0.0.0.0, DHCP chaddr: 80c1.6efa.bddb
Sep 28 13:35:30: DHCP_SNOOPING_SW: bridge packet get invalid mat entry: FFFF.FFFF.FFFF, packet is flooded to ingress VLAN: (146)
Sep 28 13:35:31: DHCPSNOOP(hlfm_set_if_input): Setting if_input to Gi0/2 for pak. Was not set
Sep 28 13:35:31: DHCPSNOOP(hlfm_set_if_input): Clearing if_input for pak. Was Gi0/2
Sep 28 13:35:31: DHCPSNOOP(hlfm_set_if_input): Setting if_input to Gi0/2 for pak. Was not set
Sep 28 13:35:31: DHCP_SNOOPING: received new DHCP packet from input interface (GigabitEthernet0/2)
Sep 28 13:35:31: DHCP_SNOOPING: process new DHCP packet, message type: BOOTPMSG, input interface: Gi0/2, MAC da: ffff.ffff.ffff, MAC sa: 00c0.b7ca.f785, IP da: 255.255.255.255, IP sa: 0.0.0.0, DHCP ciaddr: 0.0.0.0, DHCP yiaddr: 0.0.0.0, DHCP siaddr: 0.0.0.0, DHCP giaddr: 0.0.0.0, DHCP chaddr: 00c0.b7ca.f785
Sep 28 13:35:31: DHCP_SNOOPING: bridge a BOOTP packet or an unknown msg type dhcp packet, op code = 1
Sep 28 13:35:31: DHCP_SNOOPING_SW: bridge packet get invalid mat entry: FFFF.FFFF.FFFF, packet is flooded to ingress VLAN: (99)
Sep 28 13:35:33: DHCPSNOOP(hlfm_set_if_input): Setting if_input to Gi0/2 for pak. Was not set
Sep 28 13:35:33: DHCPSNOOP(hlfm_set_if_input): Clearing if_input for pak. Was Gi0/2
Sep 28 13:35:33: DHCPSNOOP(hlfm_set_if_input): Setting if_input to Gi0/2 for pak. Was not set
Sep 28 13:35:33: DHCPSNOOP(hlfm_set_if_input): Clearing if_input for pak. Was Gi0/2
Sep 28 13:35:33: DHCPSNOOP(hlfm_set_if_input): Setting if_input to Gi0/2 for pak. Was not set
Sep 28 13:35:33: DHCP_SNOOPING: received new DHCP packet from input interface (GigabitEthernet0/2)
Sep 28 13:35:33: DHCP_SNOOPING: process new DHCP packet, message type: DHCPINFORM, input interface: Gi0/2, MAC da: ffff.ffff.ffff, MAC sa: 80c1.6efa.bddb, IP da: 255.255.255.255, IP sa: 192.168.146.242, DHCP ciaddr: 192.168.146.242, DHCP yiaddr: 0.0.0.0, DHCP siaddr: 0.0.0.0, DHCP giaddr: 0.0.0.0, DHCP chaddr: 80c1.6efa.bddb
Sep 28 13:35:33: DHCP_SNOOPING_SW: bridge packet get invalid mat entry: FFFF.FFFF.FFFF, packet is flooded to ingress VLAN: (146)
Sep 28 13:35:33: DHCPSNOOP(hlfm_set_if_input): Setting if_input to Gi0/2 for pak. Was not set
Sep 28 13:35:33: DHCPSNOOP(hlfm_set_if_input): Clearing if_input for pak. Was Gi0/2
Sep 28 13:35:33: DHCPSNOOP(hlfm_set_if_input): Setting if_input to Gi0/2 for pak. Was not set
Sep 28 13:35:33: DHCP_SNOOPING: received new DHCP packet from input interface (GigabitEthernet0/2)
Sep 28 13:35:33: DHCPSNOOP(hlfm_set_if_input): Setting if_input to Gi0/2 for pak. Was not set
Sep 28 13:35:33: DHCPSNOOP(hlfm_set_if_input): Clearing if_input for pak. Was Gi0/2
Sep 28 13:35:33: DHCPSNOOP(hlfm_set_if_input): Setting if_input to Gi0/2 for pak. Was not set
Sep 28 13:35:33: DHCP_SNOOPING: received new DHCP packet from input interface (GigabitEthernet0/2)
Sep 28 13:35:33: DHCP_SNOOPING: process new DHCP packet, message type: DHCPDISCOVER, input interface: Gi0/2, MAC da: ffff.ffff.ffff, MAC sa: 6c62.6d6f.551a, IP da: 255.255.255.255, IP sa: 0.0.0.0, DHCP ciaddr: 0.0.0.0, DHCP yiaddr: 0.0.0.0, DHCP siaddr: 0.0.0.0, DHCP giaddr: 0.0.0.0, DHCP chaddr: 6c62.6d6f.551a
Sep 28 13:35:33: DHCP_SNOOPING_SW: bridge packet get invalid mat entry: FFFF.FFFF.FFFF, packet is flooded to ingress VLAN: (146)
Sep 28 13:35:33: DHCP_SNOOPING: process new DHCP packet, message type: DHCPOFFER, input interface: Gi0/2, MAC da: ffff.ffff.ffff, MAC sa: b40c.25e2.8010, IP da: 255.255.255.255, IP sa: 192.168.146.14, DHCP ciaddr: 0.0.0.0, DHCP yiaddr: 192.168.146.21, DHCP siaddr: 192.168.1.211, DHCP giaddr: 192.168.146.14, DHCP chaddr: 6c62.6d6f.551a
Sep 28 13:35:33: DHCP_SNOOPING: output port is same as input port (GigabitEthernet0/2), dropping packet

 

Interface Gi0/2 is facing our MS DHCP server (not directly connected, there are lots of other switches on the way)

I suspect those dropped packets are related to the output in bold

Can you please explain, what those bold messages mean?

6 Replies 6

marce1000
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           - FYIhttps://bst.cloudapps.cisco.com/bugsearch/bug/CSCvm45491

 M.



-- Each morning when I wake up and look into the mirror I always say ' Why am I so brilliant ? '
    When the mirror will then always repond to me with ' The only thing that exceeds your brilliance is your beauty! '

Hello,

This bug is related to 3560/3850, ours is and old Cisco IOS Software, C2960 Software (C2960-LANBASEK9-M), Version 12.2(55)SE5, RELEASE SOFTWARE (fc1)

 

VLAN: (146) & VLAN: (99)
please can you confirm that these VLAN config with dhcp snooping ?

Hello,

Yes, it is configured for all VLANs on the switch

ip dhcp snooping vlan 81,99,142,146,162,167,200,234,252,836

friend under analysis hope finish this week end 

Hello my friend

Any news? Below is ip dhcp snooping stats details. What does Unknown Output Interface and Misdirected Packets mean?

 

 

Packets Processed by DHCP Snooping = 171088
Packets Dropped Because
IDB not known = 0
Queue full = 0
Interface is in errdisabled = 0
Rate limit exceeded = 0
Received on untrusted ports = 1
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 = 98488
Misdirected Packets = 13791
Packets with Invalid Size = 0
Packets with Invalid Option = 0