Cisco SF200-24 Administration Manual page 222

Configuring IP Information
Management and IP Interfaces
Cisco Small Business 200 1. 1 Series Smart Switch Administration Guide
If the switch receives a DHCP response from the DHCP server with an IP address,
it sends Address Resolution Protocol (ARP) packets to confirm that the IP address
is unique. If the ARP response shows that the IP address is in use, the switch sends
a DHCPDECLINE message to the offering DHCP server, and sends another
DHCPDISCOVER packet that restarts the process.
If the switch does not receive a DHCP response in 60 seconds, it continues to
send DHCPDISCOVER queries, and adopts the default IP address: 192. 1 68. 1 .254/
24.
IP address collisions occur when the same IP address is used in the same IP
subnet by more than one device. Address collisions require administrative actions
on the DHCP server and/or the devices that collide with the switch.
When a VLAN is configured to use dynamic IP addresses, the switch issues DHCP
requests until it is assigned an IP address from a DHCP server. The management
VLAN can be configured with a static or dynamic IP address. The IP subnets to
which these IP addresses belong are known as directly connected/attached IP
subnets.
The IP address assignment rules for the switch are as follows:
• Unless the switch is configured with a static IP address, it issues DHCP
queries until a response is received from a DHCP server.
• If the IP address on the switch is changed, the switch issues gratuitous ARP
packets to the corresponding VLAN to check IP address collisions. This rule
also applies when the switch reverts to the default IP address.
• The system status LED changes to solid green when a new unique IP
address is received from the DHCP server. If a static IP address has been
set, the system status LED also changes to solid green. The LED flashes
when the switch is acquiring an IP address and is currently using the factory
default IP address 192. 1 68. 1 .254.
• The same rules apply when a client must renew the lease, prior to its
expiration date through a DHCPREQUEST message.
• When no statically defined or DHCP-acquired IP address is available, the
default IP address is used. When the other IP addresses becomes available,
the addresses are automatically used. The default IP address is always on
the management VLAN.
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