Cisco Cisco Access Registrar 4.2 Dokumentacja Pobierz pdf (Strona 88)

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Cisco Wireless LAN Controller Configuration Guide

OL-13826-01

Chapter 3 Configuring Ports and Interfaces

Enabling Link Aggregation

LAG simplifies controller configuration because you no longer need to configure primary and secondary

ports for each interface. If any of the controller ports fail, traffic is automatically migrated to one of the

other ports. As long as at least one controller port is functioning, the system continues to operate, access

points remain connected to the network, and wireless clients continue to send and receive data.

When configuring bundled ports on the controller, you may want to consider terminating on two different

modules within a modular switch such as the Catalyst 6500; however, Cisco does not recommend

connecting the LAG ports of a 4400 controller to multiple Catalyst 6500 or 3750G switches.

Terminating on two different modules within a single Catalyst 6500 switch provides redundancy and

ensures that connectivity between the switch and the controller is maintained when one module fails.

Figure 3-13 illustrates this use of redundant modules. A 4402-50 controller is connected to two different

Gigabit modules (slots 2 and 3) within the Catalyst 6500. The controller’s port 1 is connected to Gigabit

interface 3/1, and the controller’s port 2 is connected to Gigabit interface 2/1 on the Catalyst 6500. Both

switch ports are assigned to the same channel group.

When a 4404 controller or WiSM controller module LAG port is connected to a Catalyst 3750G or a 6500

or 7600 channel group employing load balancing, note the following:

• LAG requires the Etherchannel to be configured for the “on” mode on both the controller and the

Catalyst switch.

• Once the Etherchannel is configured as “on” at both ends of the link, it does not matter if the Catalyst

switch is configured for either Link Aggregation Control Protocol (LACP) or Cisco proprietary Port

Aggregation Protocol (PAgP) because no channel negotiation is done between the controller and the

switch. Additionally, LACP and PAgP are not supported on the controller.

• The load-balancing method configured on the Catalyst switch must be a load-balancing method that

terminates all IP datagram fragments on a single controller port. Not following this recommendation

may result in problems with access point association.

• The recommended load-balancing method for Catalyst switches is src-dest-ip (CLI command:

port-channel load-balance src_dest_ip).

• The Catalyst 6500 series switches running in PFC3 or PFC3CXL mode implement enhanced

EtherChannel load balancing. The enhanced EtherChannel load balancing adds the VLAN number

to the hash function, which is incompatible with LAG. From Release 12.2(33)SXH and later

releases, Catalyst 6500 IOS software offers the exclude vlan keyword to the port-channel

load-balance command to implement src-dst-ip load distribution. See the Cisco IOS Interface and

Hardware Component Command Reference guide for more information.

• Enter the show platform hardware pfc mode command on the Catalyst 6500 switch to confirm the

PFC operating mode.

The following example shows a Catalyst 6500 series switch in PFC3B mode when you enter the

global configuration port-channel load-balance src-dst-ip command for proper LAG

functionality:

# show platform hardware pfc mode PFC operating mode

PFC operating mode : PFC3B

# show EtherChannel load-balance

EtherChannel Load-Balancing Configuration:

src-dst-ip

The following example shows Catalyst 6500 series switch in PFC3C mode when you enter the

exclude vlan keyword in the port-channel load- balance src-dst-ip exclude vlan command.

# show platform hardware pfc mode

PFC operating mode : PFC3C

# show EtherChannel load-balance

EtherChannel Load-Balancing Configuration:

src-ip enhanced

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