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On Cisco Nexus 7000 Series Switch Cisco FabricPath domain, one switch becomes the root for the multidestination tree. Cisco FabricPath IS-IS will automatically select root switches for each multidestination tree. One of the parameters used to select the root is system ID. Which statements are true about system ID? (Choose two.)
A. System ID is a unique 12-bit SID.
B. System ID is a 48-bit value composed of the VDC MAC address.
C. Higher system ID is preferred.
D. Lower system ID is preferred.
Correct Answer: BC
Explanation/Reference:
Explanation:
Within the FabricPath domain, one switch becomes the root for the first multidestination tree in the topology (“Tree 1”). FabricPath switches compare three parameters in order to elect the root for Tree 1 in each topology, with higher values being better in all cases. The parameters, in order of preference, are:
Root priority – An 8-bit value between 0 and 255, with a default value of 64
System ID – A 48-bit value composed of the VDC MAC address (taken from the chassis midplane MAC address range)
Switch ID – The unique 12-bit Switch ID
Once a switch becomes the root for Tree 1 in a toplogy, it selects a root for each additional multidestination tree in the topology (based on the above parameters) and assigns each multidestination tree a unique FTAG value.
Reference: http://www.cisco.com/c/en/us/products/collateral/switches/nexus-7000-series-switches/white_paper_c11-687554.html (multidestination trees)
