Designing Cisco Network Service Architectures - Free Books

Another option uses 3 bits for designating the HQ building (building in some room for growth,management always grows). Using “b” for the HQ building brings us to xxxx xxxx.xxxxxbbb.rrrr ssss.hhhh hhhh.Assuming the addresses are available, we might then use 10.80-83 for the four buildings.Within each of those, we would use the third octet to indicate Layer 3 switch (first four bits)and role subnet relative to that switch. All subnets would be /24s, which keeps things simple.This scheme is somewhat wasteful of address space. There are two advantages of the scheme:1. It readily accommodates moves adds and changes of users2. It is uniform, rather than treating four HQ buildings differently.Step 5 Collocation of Web ServersThe simplest thing is to view the collocation site as a WAN extension of the Server FarmModule. That is why we ruled out managed services at the collocation facility, to avoid thecomplexity of firewalls in between the data center and the collocation facility.One design would add a pair of routers into the Server Farm Module, connecting into theaggregation or core switches within that module. The WAN links would terminate to thecollocation facility in those routers. The collocation site would run as a separate OSPF areawith summarization.If firewalls were added, routing OSPF to the firewalls is perhaps the simplest answer. There areother alternatives that are discussed later in the course.© 2007 Cisco Systems, Inc. Lab Guide 47