Ethernet Automatic Protection Switching
ExtremeWare XOS 11.3 Concepts Guide
412
Steady State
In steady state when the common link is up, both the controller and partner are said to be in the
“ready” state. After EAPS has converged and the EAPS master node has blocked its own secondary
ports, the controller puts all its ports into “forwarding,” and goes back to “ready” state.
Figure 24: Multiple EAPS domain steady state
Figure 24 shows a multiple EAPS domain steady state, where:
● EAPS1 is the EAPS domain for ring S1, S3, S4, S5, and S2
● EAPS2 is the EAPS domain for ring S1, S6, S7, S8, and S2
● EAPS3 is the EAPS domain for ring S1, S9, S10, S11, and S2
● P1, P2, P3, and P4 are the ports on switch S1
● P5, P6, P7, and P8 are the ports on switch S2
● S5, S8, and S11 are the master nodes of their respective EAPS domains
● S3, S4, S6, S7, S9, and S10 are the transit nodes of their respective EAPS domains
● S1 and S2 are running EAPSv2
● S1 is the controller
● S2 is the partner
● P1 is the EAPS shared port on switch S1
● P5 is the EAPS shared port on switch S2
● Link ID 10 is the unique identifier for the common link
Common Link Failures
If a single common link fails, the configured controller (S1) and partner (S2) take steps to prevent a
superloop.
Assuming there is a single data VLAN configured on all three EAPS domains, the controller (S1) keeps
one port open (called “Active-Open”). The remaining segment ports are “blocked” to prevent a
superloop.
In Figure 25, P2 is the “Active-Open” port on S1. Ports P3 and P4 are “blocked.” The master nodes (S5,
S8, and S11) open their secondary ports.
EX_104
S4
S5
S3
EAPS1
Partner
S9
S11
S10
S1
S2
EAPS2
EAPS3
Controller
S6
S8
S7
Master
Master
Master
P1
P5
P6
P7
P8
P2
P3
P4
Common
linklink ID=10
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