A.IPSec VPN B.SSL VPN C.port security D.port security with statically configured MAC addresses E.private VLANs
A. Make HSRP track interfaces between the edge and core routers. B. Replace HSRP with GLBP. 用GLBP替換HSRP C. Add crossed intrasite links: R1-R4, R2-R3, R5-R8, and R6-R7. D. Make R3 and R8 have lower HSRP priority than R1 and R7. E. Replace HSRP with VRRP
A.root guard B.loop guard C.BPDU guard D.UDLD E.BPDU skew detection