Cisco Catalyst 4500 Series - Troubleshooting Tips

59-15
Catalyst 4500 Series Switch, Cisco IOS Software Configuration Guide - Cisco IOS XE 3.9.xE and IOS 15.2(5)Ex
Chapter 59 Configuring the Cisco IOS DHCP Server
Configuring DHCP Address Pools
Troubleshooting Tips
If you are using secondary IP addresses under a single loopback interface and using secondary subnets
under a DHCP pool, use one DHCP pool to configure networks for all the secondary subnets instead of
using one pool per secondary subnet. The network network-number [mask | /prefix-length] [secondary]
command must be configured under a single DHCP address pool rather than multiple DHCP address
pools.
The following is the correct configuration:
ip dhcp pool dhcp_1
network 172.16.1.0 255.255.255.0
network 172.16.2.0 255.255.255.0 secondary
network 172.16.3.0 255.255.255.0 secondary
network 172.16.4.0 255.255.255.0 secondary
!
interface Loopback111
ip address 172.16.1.1 255.255.255.255 secondary
Step 16
Switch(dhcp-config)# network
network-number [mask | /prefix-length]
[secondary]
(Optional) Specifies the network number and mask of a secondary
DHCP server address pool.
• Any number of secondary subnets can be added to a DHCP
server address pool.
• During execution of this command, the configuration mode
changes to DHCP pool secondary subnet configuration mode,
which is identified by (config-dhcp-subnet-secondary)#
prompt. In this mode, the administrator can configure a
default device list that is specific to the subnet.
• See Troubleshooting Tips section if you are using secondary
IP addresses under a loopback interface with DHCP
secondary subnets.
Step 17
Switch(config-dhcp-subnet-secondary)#
override default-router address [ address2
... address8]
(Optional) Specifies the default device list that is used when an IP
address is assigned to a DHCP client from a particular secondary
subnet.
• If the subnet-specific override value is configured, this
override value is used when assigning an IP address from the
subnet; the network-wide default device list is used only to
set the gateway device for the primary subnet.
• If this subnet-specific override value is not configured, the
network-wide default device list is used when assigning an IP
address from the subnet.
Step 18
Switch(config-dhcp-subnet-secondary)#
override utilization high
percentage-number
(Optional) Sets the high utilization mark of the subnet size.
• This command overrides the global default setting specified
by the utilization mark high command.
Step 19
Switch(config-dhcp-subnet-secondary)#
override utilization low
percentage-number
(Optional) Sets the low utilization mark of the subnet size.
• This command overrides the global default setting specified
by the utilization mark low command.
Step 20
Switch(config-dhcp-subnet-secondary)# end
Exits DHCP secondary subnet configuration mode and returns to
privileged EXEC mode.
Command or Action Purpose