Either way, there is no possibility of temporary loops. When the link
or bridge recovers, then normal operation resumes.
406 Chapter 13
In the event that the server network becomes split into two parts, connected only
through the two links of server cloud, then the network remains divided because the
client cloud never enables more than one connection to the server cloud. This is a purposeful
limitation. The most likely reason for the server cloud to use the client cloud
as the principle data highway is a configuration blunder. In the case of a single-edge
bridge connected to a core cloud, such errors are most common in the bridges that are
most often configured, namely, as the edge bridges.
To see the power of this idea, let??™s assume that the server cloud in Figure 13.13 consists
of 802.1ad provider bridges (802.1ah MAC-in-MAC bridges would work similarly).
Let??™s also suppose that the provider is offering two EVCs. The provider edge bridges??™
C-components are encapsulating all of the customer??™s odd-numbered C-VLANs into
S-VLAN 20, and the even-numbered C-VLANs into S-VLAN 21, as shown in Figure 13.7.
Suppose customer cloud 1 determines that the odd-numbered VLANs will use the
A-C link and that the even-numbered VLANs will use the B-D link.
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