You are using two 16 Gbps and two 8 Gbps ISLs to connect two Brocade DCX 8510-8s.
Which statement is true?
A.
Default link cost of all links is 500.
B.
Default link cost of all links is 1000.
C.
Default link cost of the 16 Gbps links is 250.
D.
Default link cost of the 8 Gbps links is 250.
Explanation:
FSPF link cost calculation when ARL is used
Fabric Shortest Path First (FSPF) is a link state path selection protocol that directs traffic along the shortest path between the source and destination based upon the link cost. When ARL is used, the link cost is equal to the sum of the maximum traffic rates of all established, currently active low metric circuits in the tunnel. The following formulas are used:
If the bandwidth is greater than or equal to 2 Gbps, the link cost is 500.
If the bandwidth is less than 2 Gbps, but greater than or equal to 1 Gbps, the link cost is 1,000,000 divided by the bandwidth in Mbps.
If the bandwidth is less than 1 Gbps, the link cost is 2000 minus the bandwidth in Mbps.
When running multiple parallel tunnels, set the static link costs if you want all tunnels used at all times. Otherwise, a circuit outage can take a tunnel out of service because of a link cost change. If multiple parallel tunnels are used, configure Lossless DLS. This avoids circuit bounce because of disruptive bandwidth updates.
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