Refer to the exhibit. The 2.6.6.6/32 prefix is flapping when PE1 is flapping. Which action can fix this issue?
A. On PE2, allow only redistribution from BGP into IS-IS; on PE3, allow only redistribution from ISOS into BGP.
B. Configure all IS-IS instances as level-1-only.
C. Configure a sham link between PE2 and PE3.
D. On PE2 and PE3, reconfigure redistribute BGP into IS-IS using the metric-type external parameter.
