Troubleshooting
The DHCP client continually sends requests instead of a discover
This happens when the client is renewing its lease or, for whatever reason, believes that should be issued a specific address. If the client does not receive either an ACK or NACK (from a DHCP server) then the client will continue to request the address.
A NACK should cause the client to send a discover packet instead of a request. Hence, if NACK is not received, the client (depending on its DHCP software) may continue to request an address and never send a discover.
Maximum number of leases is exceeded
By default, there is one lease per switch port. If there is already an entry for a port in the DHCP snooping database (in the current valid entries), then the next request on that port from a different MAC address will see the DHCP server ACK discarded:
DHCPSN_Process: [0b47d60c] DHCP Snooping pkt for VLAN 1 | from port 3 | |
DHCPSN_Process: [0b47d60c] Type: REQUEST |
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DHCPSN_Process: [0b47d60c] On DHCP Snooping | port | |
DHCPSN_Process: [0b47d60c] DHCP Snoop forwarding pkt at | L2 for VLAN 1 InPort 3 | |
DHCPSN_Process: [0b47d60c] L2 Dest MAC is broadcast |
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DHCPSN_Process: [0b47d60c] Type: REQUEST, L2 forward to | trusted ports | |
DHCPSN_Process: [0b47d60c] Forward ports (except 3) |
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DHCPSN_Process: [0b47d60c] | Tagged:None |
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DHCPSN_Process: [0b47d60c] | Untagged:48 |
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DHCPSN_Process: [0b47de2c] DHCP Snooping pkt for VLAN 1 | from port 48 | |
DHCPSN_Process: [0b47de2c] Type: REPLY |
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DHCPSN_Process: [0b47de2c] On DHCP Snooping trusted port
DHCPSN_Process: [0b47de2c] Lookup result for CHAddr
DHCPSN_Process: [0b47de2c] DHCP Snoop forwarding pkt at L2 for VLAN 1 InPort 48
DHCPSN_Process: [0b47de2c] L2 Dest MAC is unicast
DHCPSN_Process: [0b47de2c] Using chaddr lookup result for dest port(s)
DHCPSN_Process: [0b47de2c] L2 forward packet directly to port 3
DHCPSN_Process: [0b47de2c] Forward ports (except 48)
DHCPSN_Process: [0b47de2c] | Tagged:None |
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DHCPSN_Process: [0b47de2c] | Untagged:3 |
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DHCPSN_Process: [0b47e64c] DHCP Snooping pkt for VLAN 1 | from port 3 | |
DHCPSN_Process: [0b47e64c] Type: REQUEST |
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DHCPSN_Process: [0b47e64c] On DHCP Snooping | port | |
DHCPSN_Process: [0b47e64c] DHCP Snoop forwarding pkt at | L2 for VLAN 1 InPort 3 | |
DHCPSN_Process: [0b47e64c] L2 Dest MAC is broadcast |
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DHCPSN_Process: [0b47e64c] Type: REQUEST, L2 forward to | trusted ports | |
DHCPSN_Process: [0b47e64c] Forward ports (except 3) |
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DHCPSN_Process: [0b47e64c] | Tagged:None |
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DHCPSN_Process: [0b47e64c] | Untagged:48 |
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DHCPSN_Process: [0b47ee6c] DHCP Snooping pkt for VLAN 1 from port 48
DHCPSN_Process: [0b47ee6c] Type: REPLY
DHCPSN_Process: [0b47ee6c] On DHCP Snooping trusted port
DHCPSN_Process: [0b47ee6c] Lookup result for CHAddr
DHCPSN_Process: [0b47ee6c] DHCP ACK Found...
DHCPSN_DB: Updating entryId 7. Flags 00000010
DHCPSN_DB: Couldn't update: Listener error or will exceed MAXLEASES on port 3 (Current/ MAX 1/1)
DHCPSN_Process: [0b47ee6c] Error adding entry to DB
DHCPSN_Process: [0b47ee6c] Discard packet, DHCP ACK not forwarded
Page 21 AlliedWare™ OS How To Note: DHCP Snooping on