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Page 21 | AlliedWare™ OS How To Note: DHCP Snooping on Rapier-style switches
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
DHCPSN_Process: [0b47d60c] On DHCP Snooping non-trusted port
DHCPSN_Process: [0b47d60c] DHCP Snoop forwarding pkt at L2 for VLAN 1 InPort 3
DHCPSN_Process: [0b47d60c] L2 Dest MAC is broadcast
DHCPSN_Process: [0b47d60c] Type: REQUEST, L2 forward to trusted ports
DHCPSN_Process: [0b47d60c] Forward ports (except 3)
DHCPSN_Process: [0b47d60c] Tagged:None
DHCPSN_Process: [0b47d60c] Untagged:48
DHCPSN_Process: [0b47de2c] DHCP Snooping pkt for VLAN 1 from port 48
DHCPSN_Process: [0b47de2c] Type: REPLY
DHCPSN_Process: [0b47de2c] On DHCP Snooping trusted port
DHCPSN_Process: [0b47de2c] Lookup result for CHAddr 00-00-00-00-00-01: Port 3
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
DHCPSN_Process: [0b47de2c] Untagged:3
DHCPSN_Process: [0b47e64c] DHCP Snooping pkt for VLAN 1 from port 3
DHCPSN_Process: [0b47e64c] Type: REQUEST
DHCPSN_Process: [0b47e64c] On DHCP Snooping non-trusted port
DHCPSN_Process: [0b47e64c] DHCP Snoop forwarding pkt at L2 for VLAN 1 InPort 3
DHCPSN_Process: [0b47e64c] L2 Dest MAC is broadcast
DHCPSN_Process: [0b47e64c] Type: REQUEST, L2 forward to trusted ports
DHCPSN_Process: [0b47e64c] Forward ports (except 3)
DHCPSN_Process: [0b47e64c] Tagged:None
DHCPSN_Process: [0b47e64c] Untagged:48
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 00-00-00-00-00-01: Port 3
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