Netgear XCM8806 Chassis User Manual - Page 542

NETGEAR 8800 User Manual desirable to have multiple STP domains operating in a single VLAN, one for each looped area. The justifications include the following: • The complexity of the STP algorithm increases, and performance drops, with the size and complexity of the network. The 802.1D standard specifies a maximum network diameter of seven hops. By segregating a big VLAN into multiple STPDs, you reduce complexity and enhance performance. • Local to each site, there may be other smaller VLANs that share the same redundant looped area with the large VLAN. Some STPDs must be created to protect those VLANs. The ability to partition VLANs allows the large VLAN to be "piggybacked" in those STPDs in a site-specific fashion. Figure 38 has five domains. VLANs green, blue, brown, and yellow are local to each domain. VLAN red spans all of the four domains. Using a VLAN that spans multiple STPDS, you do not have to create a separate domain for VLAN red. Instead, VLAN red is "piggybacked" onto those domains local to other VLANs. VLAN red S1 VLAN green S2 VLAN red S3 VLAN blue VLAN yellow VLAN red VLAN red VLAN brown S4 EX_051 Figure 38. VLANs Spanning Multiple STPDs In addition, the configuration in Figure 38 has these features: • Each site can be administered by a different organization or department within the enterprise. Having a site-specific STP implementation makes the administration more flexible and convenient. • Between the sites the connections usually traverse distribution switches in ways that are known beforehand to be "safe" with STP. In other words, the looped areas are already well-defined. EMISTP Deployment Constraints Although EMISTP greatly enhances STP capability, these features must deployed with care. This section describes configuration issues that, if not followed, could lead to an improper deployment of EMISTP. This section also provides the following restrictive principles to abide by in network design: 542 | Chapter 18. STP