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858 PowerConnect B-Series FCX Configuration Guide
53-1002266-01
Configuring IP parameters – Layer 3 Switches
26
3. If the device has a dynamic address, the device asks the DHCP server to validate that address.
If the server does not respond, the device will continue to use the existing address until the
lease expires. If the server responds, and the IP address is outside of the DHCP address pool
or has been leased to another device, it is automatically rejected, and the device receives a
new IP address from the server. If the existing address is valid, the lease continues.
NOTE
The lease time interval is configured on the DHCP server, not on the client device. The ip
dhcp-client lease command is set by the system, and is non-operational to a user.
4. If the existing address is static, the device keeps it and the DHCP Client process is ended.
5. For a leased IP address, when the lease interval reaches the renewal point, the device
requests a renewal from the DHCP server:
• If the device is able to contact the DHCP server at the renewal point in the lease, the DHCP
server extends the lease. This process can continue indefinitely.
• If the device is unable to reach the DHCP server after four attempts, it continues to use the
existing IP address until the lease expires. When the lease expires, the dynamic IP address
is removed and the device contacts the DHCP server for a new address. If the device is
still unable to contact the DHCP server after four attempts, the process is ended.
The TFTP Flash image download and update step
NOTE
This process only occurs when the client device reboots, or when DHCP-client has been disabled and
then re-enabled.
Once a lease is obtained from the server (described in “The IP address validation and lease
negotiation step” on page 857), the device compares the filename of the requested flash image
with the image stored in flash. In a stacking configuration, the device compares the filename with
the image stored in the Active controller only.
• If the .bin filenames match, then the DHCP client skips the flash image download. If
auto-configuration is enabled, the DHCP client proceeds with downloading the configuration
files as described in “The TFTP configuration download and update step”.
• If the .bin filenames are different, then the DHCP client downloads the new image from a TFTP
server, then writes the downloaded image to flash. In a stacking configuration, the device
copies the flash image to flash in all stack member units.
The code determines which flash (i.e., primary or secondary) to use based on how the device is
booted. In a stacking configuration, the member units use the same flash as the Active
controller. Once the flash is updated with the newer flash image, the device is reloaded and
any member units in a stacking configuration are reloaded as well. If auto-configuration is
enabled, the DHCP client then proceeds to download the configuration files described in “The
TFTP configuration download and update step”.
NOTE
In a stacking environment, the DHCP client flash image download waits 5 minutes for all
member units to join and update. Then the DHCP client downloads the new image from the
TFTP server using the TFTP server IP address (option 150), if it is available. If the TFTP server IP
address is not available, the DHCP client requests the TFTP file from the DHCP server.