Config example for a Cisco 4500 / 6500 Switch

interface Port-channel21
description ESX1 4 port aggregate
switchport
switchport trunk encapsulation dot1q
switchport trunk allowed vlan 1,3,4,9
switchport mode trunk
switchport nonegotiate
spanning-tree portfast trunk
!
interface GigabitEthernet3/19
description ESX1 4 port link aggregate
switchport trunk encapsulation dot1q
switchport trunk allowed vlan 1,3,4,9
switchport mode trunk
switchport nonegotiate
spanning-tree portfast trunk
channel-group 21 mode desirable
!
interface GigabitEthernet3/20
description ESX1 4 port link aggregate
switchport trunk encapsulation dot1q
switchport trunk allowed vlan 1,3,4,9
switchport mode trunk
switchport nonegotiate
spanning-tree portfast trunk
channel-group 21 mode desirable
!
interface GigabitEthernet4/19
description ESX1 4 port link aggregate
switchport trunk encapsulation dot1q
switchport trunk allowed vlan 1,3,4,9
switchport mode trunk
switchport nonegotiate
spanning-tree portfast trunk
channel-group 21 mode desirable
!
interface GigabitEthernet4/20
description ESX1 4 port link aggregate
switchport trunk encapsulation dot1q
switchport trunk allowed vlan 1,3,4,9
switchport mode trunk
switchport nonegotiate
spanning-tree portfast trunk
channel-group 21 mode desirable
!

Thanks to:

http://www.switzerbusinesssolutions.com/information/technology-articles/7-infrastructure/12-vmware-esx-and-cisco-trunking-and-vlaning.html