Case Study

Figure 19-11 illustrates a redundant LAN and WAN infrastructure.

Figure 19-11. Redundant Network #1

The redundant components in this configuration are as follows:

• Dual and diverse Ethernet network segments are used.

• Dual NICs are used, with each card attaching to one of the diverse Ethernet network segments.

• Each Ethernet network segment is attached to a Cisco Catalyst Switch; such as the 6000 Series.

• Each Catalyst switch is served by two WAN routers.

• Each WAN router is attached to the network service provider:

  - Cisco's HSRP creates a single (virtual) address to which the LAN devices connect, enabling two or more Cisco routers to be viewed as a single router interface to the LAN.

  - The same network service provider can be used for the redundant WAN link, or a second (diverse) network service provider can be used to provide this redundant link.

  - Both the primary and redundant WAN link can be connected to the same WAN router, but this configuration makes the WAN router a single point of failure and therefore should be carefully considered.