When you execute the "ip helper-address" command on a router， which three UDP ports getenabled automatically by default？（）

A.IP Helper is used to direct BOOTP clients to a BOOTP server
B.IP Helper is used to prevent the router form forwarding IP broadcasts
C.IP Helper is used to allow IPX clients to communicate with IP-based servers
D.IP Helper is used to accommodate compatibility routers using different IP routing protocols
E.None of the other alternatives apply

A.OSPF and RIP use the same major network 172.16.0.0. Therefore， the keywordsubnets is notrequired to redistribute protocols into OSPF
B.Because OSPF has a longer mask for the same major network than RIP and because RIPversion 1 is being used， none of the routes learned from OSPF will be advertised into RIP
C.The metric for the OSPF routes that are redistributed into RIP is too low， a fact that preventsOSPF routes from being advertised into RIP
D.The process of redistribution of RIP into OSPF does not require any metric conversion， so thereis no need to define the metric using the default-metric command during the redistribution

A.Set the OSPF default metric to 20
B.Apply an inbound ACL to the R2 serial interface
C.Configure distribute-lists on R3 and R4
D.Change the RIP administrative distance on R3 to 110
E.Change the OSPF administrative distance on R3 to 110
F.None of the other alternatives apply