Which ACL permits OSPF type 5 LSAs for 132.108.2.0 and .3.0?

Why the Answer Is Correct

A is correct because option A's wildcard mask 0.0.3.255 expands the ACL to cover 132.108.0.0 through 132.108.3.255, which includes both missing networks: 132.108.2.0/24 and 132.108.3.0/24. In an OSPF distribute-list scenario, the ACL must match the network addresses of the external LSAs that should be allowed; if either prefix is outside the permit range, R1 never receives its type 5 LSA. Because A includes both external subnets while no narrower or offset entry does, it is the only command that resolves the reported loss. The community consensus is unanimous on this, with alexnadal99 calling A "the only possible option."

Why the Other Options Are Wrong

Option B covers only 132.108.0.0–132.108.1.255, so neither 132.108.2.0/24 nor 132.108.3.0/24 is permitted. Option C uses 132.108.4.0 0.0.3.255, which matches the 132.108.4.0–132.108.7.255 range, the wrong side of the /22 boundary; as dancott put it, "C gives subnets.4.0 to.7.254". Option D permits exactly 132.108.2.0/24, so only one of the two type 5 LSAs is allowed and 132.108.3.0/24 remains missing. Thus B, C, and D each fail to include both advertised external networks.

Community Comment Notes

Several voters independently validated the range math. dancott and Commando1664 both noted that option C points to the.4.0–.7.255 block rather than the needed.0.0–.3.255 range. alexnadal99 described A as "the only possible option," and Chiaretta simply agreed that "A is right." Pietjeplukgeluk and Defilet also voted A, reinforcing that the community sees no ambiguity here.