VLSM and ACL Issues

VLSM and ACL issues are relatively common in networking. One of the main issues with VLSM and ACLs is related to the overlapping of subnets. This occurs when a more specific subnet falls within a less specific subnet, leading to issues with routing and access control.

For example, if there are two subnets, 10.0.0.0/24 and 10.0.0.0/25, and an ACL is configured to allow traffic from the 10.0.0.0/24 subnet but deny traffic from the 10.0.0.0/25 subnet, traffic from the more specific subnet will still be denied because it falls within the range of the less specific subnet.

To avoid these issues, it is important to carefully plan and configure VLSM and ACLs. This includes avoiding overlapping subnets, using more specific ACL rules for more specific subnets, and testing the configuration thoroughly to ensure proper routing and access control. When troubleshooting VLSM and ACL issues, the ping and traceroute commands can be helpful in identifying connectivity problems and determining where traffic is being blocked. It is also important to check the ACL configuration and verify that there are no overlapping subnets or conflicting rules.