The suggested answer is B, D.
This document describes how Cisco Express Forwarding (CEF) polarization can cause suboptimal use of redundant paths to a destination network. CEF polarization is the effect when a hash algorithm chooses a particular path and the redundant paths remain completely unused.
How to Avoid CEF Polarization -
The hash algorithm load-balances this way by default:
1: 1
2: 7-8
3: 1-1-1
4: 1-1-1-2
5: 1-1-1-1-1
6: 1-2-2-2-2-2
"Pass Any Exam. Any Time." - www.actualtests.com 13
7: 1-1-1-1-1-1-1
8: 1-1-1-2-2-2-2-2
The number before the colon represents the number of equal-cost paths. The number after the colon represents the proportion of traffic which is forwarded per path.
This means that:
This illustrates that, when there is even number of ECMP links, the traffic is not load-balanced.
Reference: http://www.cisco.com/c/en/us/support/docs/ip/express-forwarding-cef/116376- technote-cef-00.html
