Cisco SF500-24 Administration Manual page 320

IP Configuration
IPv4 Management and Interfaces
STEP 6
Cisco 500 Series Stackable Managed Switch Administration Guide Release 1.3
Device forwards DHCPOFFER, DHCPACK, or DHCPNAK.
The following summarizes how DHCP packets are handled from both trusted and
untrusted ports. The DHCP Snooping Binding database is stored in non-volatile
memory.
DHCP Snooping Packet Handling
Packet Type
DHCPDISCOVER
DHCPOFFER
DHCPREQUEST
DHCPACK
DHCPNAK
DHCPDECLINE
Arriving from
Untrusted Ingress
Interface
Forward to trusted
interfaces only.
Filter.
Forward to trusted
interfaces only.
Filter.
Filter.
Check if there is
information in the
database. If the
information exists and
does not match the
interface on which the
message was
received, the packet
is filtered. Otherwise
the packet is
forwarded to trusted
interfaces only, and
the entry is removed
from database.
Arriving from Trusted Ingress
Interface
Forwarded to trusted interfaces
only.
Forward the packet according to
DHCP information. If the
destination address is unknown
the packet is filtered.
Forward to trusted interfaces
only.
Same as DHCPOFFER and an
entry is added to the DHCP
Snooping Binding database.
Same as DHCPOFFER. Remove
entry if exists.
Forward to trusted interfaces only
17
302