DHCP on a router
! UDP broadcasts coming in E0 will be forwarded as unicasts to 10.1.2.202.
! The source IP will be changed to 10.1.1.255, so that the reply packets will be
! broadcast back out E0.
interface Ethernet1
ip address 10.1.1.1 255.255.255.0
ip helper-address 10.1.2.202
! Below, an alternative configuration, with R1 as the DHCP server. R1 assigns IP
! addresses other than the excluded first 20 IP addresses in the subnet, and informs the
! clients of their IP addresses, mask, DNS, and default router. Leases are for 0 days,
! 0 hours, and 20 minutes.
ip dhcp excluded-address 10.1.1.0 10.1.1.20
!
ip dhcp pool subnet1
network 10.1.1.0 255.255.255.0
dns-server 10.1.2.203
default-router 10.1.1.1
lease 0 0 20
HSRP:
! First, on Router R1, a tracking object must be configured so that
! HSRP can track the interface state.
track 13 interface Serial0/0.1 line-protocol
! Next, on Router R1, two HSRP groups are configured. R1 has a higher priority
! in group 21, with R2 having a higher priority in group 22. R1 is set to preempt
! in group 21, as well as to track interface s0/0.1 for both groups.
interface FastEthernet0/0
ip address 10.1.1.2 255.255.255.0
standby 21 ip 10.1.1.21
standby 21 priority 105
standby 21 preempt
standby 21 track 13
standby 22 ip 10.1.1.22
standby 22 track 13
! Next, R2 is configured with a higher priority for HSRP group 22, and with
! HSRP tracking enabled in both groups. The tracking “decrement” used by R2,
! when S0/0.1 fails, is set to 9 (instead of the default of 10).
! A tracking object must be configured first, as on R1.
track 23 interface Serial0/0.1 line-protocol
interface FastEthernet0/0
ip address 10.1.1.1 255.255.255.0
standby 21 ip 10.1.1.21
standby 21 track 23
standby 22 ip 10.1.1.22
standby 22 priority 105
standby 22 track 23 decrement 9
Another HSRP
Switch(config-if)# standby group ip ip-address [secondary]
Switch(config-if)# standby group priority priority
Switch(config-if)# standby group timers [msec] hello [msec] holdtime
Switch(config-if)# standby group preempt [delay [minimum seconds] [reload seconds]]
Switch(config-if)# standby group authentication string
HSRP key chain for md5:
Switch(config-if)# standby group authentication md5 key-string [0 | 7] string
Switch(config)# key chain chain-name
Switch(config-keychain)# key key-number
Switch(config-keychain-key)# key-string [0 | 7] string
Switch(config)# interface type mod/num
Switch(config-if)# standby group authentication md5 key-chain chain-name
Tracking
Switch(config-if)# standby group track type mod/num [decrementvalue]
VRRP:
CatalystA(config)# interface vlan 50
CatalystA(config-if)# ip address 192.168.1.10 255.255.255.0
CatalystA(config-if)# vrrp 1 priority 200
CatalystA(config-if)# vrrp 1 ip 192.168.1.1
CatalystA(config-if)# vrrp 2 priority 100
CatalystA(config-if)# no vrrp 2 preempt
CatalystA(config-if)# vrrp 2 ip 192.168.1.2
GLBP:
Switch(config-if)# glbp group ip [ip-address [secondary]]
Switch(config-if)# glbp group priority level
Switch(config-if)# glbp group preempt [delay minimum seconds]
Switch(config-if)# glbp group timers [msec] hellotime [msec] holdtime
Switch(config-if)# glbp group timers redirect redirect timeout
GLBP tracking:
Switch(config)# track object-number interface type mod/num {line-protocol | ip routing}
Switch(config-if)# glbp group weighting maximum [lower lower] [upper upper]
Switch(config-if)# glbp group weighting track object-number [decrement value]
GLBP load balancing type
Switch(config-if)# glbp group load-balancing [round-robin | weighted | host-dependent]