JUNOS High Availability

A Simple Enterprise Network

A simple enterprise network design relies on routers, firewalls, and switches, as shown in Figure 1-1. The design provides filtering and separation of traffic to support a pair of employee local area networks (LANs), a pair of sensitive corporate LANs that support connectivity among corporate data stores, and a pair of demilitarized zone (DMZ) LANs that support the company’s web presence.

While this design is quite common, you’ll notice immediately that it has multiple single points of failure. All Internet connectivity is provided by a single router through a single connection to the Internet. All Internet access to the DMZ LANs is provided by a single firewall. The employee LANs reside behind another router, itself an additional single point of failure. Finally, the sensitive corporate LANs are connected using an additional firewall, which because of the linear design of the network, must push traffic through no fewer than three other single points of failure in order to send data from the corporate LANs to the regular Internet. The complete reliance on multiple single points of failure in this design results in a total lack of fault tolerance on the network.

Figure 1-1. A simple enterprise network design

Table 1-1 lists the chassis that provide the base functionality and is used to calculate a representative “cost” for this simple network. The cost calculation includes all switches, routers, and firewall products shown in the data transport path. This calculation also includes a representative cost of labor and materials for fiber optic connections within the office in which the network is located.

Table 1-1. Representative cost of a simple network

Line item	Description	Qty
1	Router 1 with interface cards and one year of vendor support	1
2	Firewall 1 with interface cards and one year of vendor support	1
3	Router 2 with interface cards and one year of vendor support	1
4	Firewall 2 with interface cards and one year of vendor support	1
5	Switch 1 and one year of vendor support	6
6	Multimode fiber trunk (materials and installation)	10
7	Facility power and cooling for one year	1
Total representative cost = $100,000