IPv4 ACL and firewall rule generator
Build one explicit rule using any, an IPv4 host or an IPv4 CIDR network. TCP and UDP rules can also match one destination port or an inclusive range.
An ACL rule is a match condition plus an action
An IPv4 ACL or firewall-filter rule typically evaluates fields such as protocol, source address, destination address and, for TCP or UDP, transport-layer ports. When a packet matches the rule, the configured action is taken. The exact processing model still depends on the platform, feature, chain or interface where the rule is used.
Rule order can change the result completely
Packet filters are order-sensitive. A broad rule placed before a specific one can make the later rule unreachable in practice. Cisco ACLs and RouterOS filter chains are evaluated in rule order, so generated configuration must be inserted at the intended position instead of being pasted blindly at the end of an existing policy.
Cisco extended ACLs use wildcard masks for IPv4 networks
In a Cisco extended IPv4 ACL, a host can be written with the host keyword, any represents any address and an IPv4 network is represented by a network address followed by a wildcard mask. For example, 192.0.2.0/24 becomes 192.0.2.0 0.0.0.255. TCP and UDP destination ports can use operators such as eq and range.
RouterOS chains describe where the packet is being filtered
The RouterOS filter table has built-in input, forward and output chains. Input covers traffic destined to the router itself, forward covers traffic passing through the router and output covers traffic generated by the router. Choosing the wrong chain can produce a syntactically valid rule that does not protect the intended traffic path.
Huawei advanced ACLs can match protocol, addresses and ports
Huawei VRP advanced ACLs are designed to match IPv4 packet characteristics including source and destination addresses, IP protocol and TCP or UDP ports. Huawei product families and VRP releases can differ in how an ACL is bound to an interface or consumed by a traffic policy, so this generator deliberately separates rule creation from deployment context.
The generator normalizes CIDR before producing vendor syntax
If you enter a network such as 192.0.2.37/24, the network is normalized to 192.0.2.0/24 before generation. Cisco and Huawei output then use the corresponding wildcard 0.0.0.255, while RouterOS keeps CIDR notation. This prevents host bits accidentally typed in a network field from being reproduced as if they were the network boundary.
Do not assume the same unmatched-packet behavior on every platform
Cisco IPv4 ACLs have an implicit deny at the end: traffic that reaches the end without matching a permit entry is denied. RouterOS filter chains behave differently: according to MikroTik documentation, if a packet reaches the end of a chain without matching a rule, it is accepted. Treating these models as equivalent can create an outage or an unintended security gap.
Generate first, review policy second, deploy last
Before deploying an ACL remotely, verify the management path, existing rule order, routing direction and rollback method. A correct deny rule applied to the wrong interface, chain or direction can immediately interrupt administrative access or production traffic. The generated command is therefore configuration assistance, not an automatic deployment instruction.