dhcp snooping problem with 3560 access switch

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Sep 19th, 2007
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Hi


I configured the switch with the following commands:


[global]

ip dhcp snooping vlan 145,360-650

no ip dhcp snooping information option

ip dhcp snooping


[uplink interface]

ip dhcp snooping trust


3550 switches are working without any problems but with 3560 switches I get the following errors:




Sep 19 14:57:09.780: DHCPSNOOP(hlfm_set_if_input): Setting if_input to Gi0/1 for pak. Was not set

Sep 19 14:57:09.780: DHCP_SNOOPING: received new DHCP packet from input interface (GigabitEthernet0/1)

Sep 19 14:57:09.780: DHCP_SNOOPING: process new DHCP packet, message type: DHCPREQUEST, input interface: Gi0/1, MAC da: ffff.ffff.ffff, MAC sa: 0015.580b.454a, 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: 0015.580b.454a

Sep 19 14:57:09.780: DHCP_SNOOPING_SW: bridge packet get invalid mat entry: FFFF.FFFF.FFFF, packet is flooded to ingress VLAN: (410)

Sep 19 14:57:09.780: DHCP_SNOOPING: process new DHCP packet, message type: DHCPACK, input interface: Gi0/1, MAC da: ffff.ffff.ffff, MAC sa: 0011.5d36.2000, IP da: 255.255.255.255, IP sa: 10.9.5.254, DHCP ciaddr: 0.0.0.0, DHCP yiaddr: 10.9.4.39, DHCP siaddr: 147.88.160.140, DHCP giaddr: 10.9.5.254, DHCP chaddr: 0015.580b.454a

Sep 19 14:57:09.780: DHCP_SNOOPING_SW: lookup packet destination port failed to retrieve source interface idb, mac: 0015.580b.454a, mat entry type: 1, port cookie: 53487336

Sep 19 14:57:09.780: DHCP_SNOOPING: can't find client's destination port, packet is assumed to be not from local switch, no binding update is needed.

Sep 19 14:57:09.780: DHCP_SNOOPING_SW: lookup packet destination port failed to retrieve source interface idb, mac: 0015.580b.454a, mat entry type: 1, port cookie: 53487336

Sep 19 14:57:09.780: DHCP_SNOOPING: can't find output interface for dhcp reply. the message is dropped.

Sep 19 14:57:09.788: DHCPSNOOP(hlfm_set_if_input): Setting if_input to Gi0/1 for pak. Was not set

Sep 19 14:57:09.788: DHCPSNOOP(hlfm_set_if_input): Clearing if_input for pak. Was Gi0/1

Sep 19 14:57:09.788: DHCPSNOOP(hlfm_set_if_input): Setting if_input to Gi0/1 for pak. Was not set


What could be the problem???


IOS 3550 = 12.2(25)SEC

IOS 3560 = 12.2(25)SEC


Thanx

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htarra Tue, 09/25/2007 - 07:11
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I think it prevents the switch from inserting Option 82 header into the DHCP packet while forwarding. If DHCP option 82 information is being inserted, upstream routed interfaces must be configured with a trust relationship to the downstream DHCP snooping switches that add option 82. This is done with the IP DHCP relay information trusted command, in the VLAN interface configuration toward the downstream switch.

schmij01 Tue, 09/25/2007 - 07:48
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Those messages are debug log messages. Are you debugging DHCP snooping? What exactly is the problem you are having on the 3560?


FYI, that output looks normal to me. A DHCP request is being broadcast from a client that is upstream on the uplink (gi0/1). This switch is seeing that. Then a DHCP reply is seen via broadcast. The switch sees that too. Since the client is not local to the switch, it is ignoring the DHCP reply.

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