Rockwell Automation Publication 1783-UM007G-EN-P - February 2017 223
Configure Switch Features Chapter 7
DHCP snooping for a ring can be enabled or disabled. By default, DHCP
snooping for a ring is enabled:
• When enabled, DHCP snooping prevents DHCP address assignments
from going beyond an active ring DCHP server and the devices within
the ring. DHCP requests from another server cannot enter the ring, and
DHCP requests from the active ring DCHP server cannot leave the
ring.
• When disabled, DHCP snooping lets the active ring DHCP server
forward DHCP requests outside of the ring. However, DHCP requests
passed around the ring from a ring device are never passed to devices
connected to the backup DHCP server. The requests are treated as ring
traffic and stay in the ring.
Figure 19 on page 224 shows two Stratix 5700 switches that are configured for
DHCP in a ring:
• Ring device 1 is the active ring supervisor and ring DHCP server.
• Ring device 2 is the backup ring supervisor and ring DHCP server.
• Ring devices 2 and 5 have statically-assigned IP addresses and appear as
blank entries in DHCP table (
Table 43).
• Ring devices 3 and 6 are configured to receive IP addresses from
BOOTP.
• Ring device 4 is configured to receive IP addresses from DHCP.
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