Connectivity Guide

Access Control Lists
OS10 uses two types of access policies — hardware-based ACLs and software-based route-maps. Use an ACL to lter trac and drop or
forward matching packets. To redistribute routes that match congured criteria, use a route-map.
ACLs
ACLs are a lter containing criterion to match; for example, examine internet protocol (IP), transmission control protocol (TCP), or user
datagram protocol (UDP) packets, and an action to take such as forwarding or dropping packets at the NPU. ACLs permit or deny trac
based on MAC and/or IP addresses. The number of ACL entries is hardware-dependent.
ACLs have only two actions — forward or drop. Route-maps not only permit or block redistributed routes but also modify information
associated with the route when it is redistributed into another protocol. When a packet matches a lter, the device drops or forwards the
packet based on the lter’s specied action. If the packet does not match any of the lters in the ACL, the packet drops, an implicit deny.
ACL rules do not consume hardware resources until you apply the ACL to an interface.
ACLs process in sequence. If a packet does not match the criterion in the rst lter, the second lter applies. If you congure multiple
hardware-based ACLs, lter rules apply on the packet content based on the priority numeric processing unit (NPU) rule.
Route maps
Route-maps are software-based protocol ltering redistributing routes from one protocol to another and used in decision criterion in route
advertisements. A route-map denes which of the routes from the specied routing protocol redistributes into the target routing process,
see Route-maps.
Route-maps which have more than one match criterion, two or more matches within the same route-map sequence, have dierent match
commands. Matching a packet against this criterion is an AND operation. If no match is found in a route-map sequence, the process moves
to the next route-map sequence until a match is found, or until there are no more sequences. When a match is found, the packet forwards
and no additional route-map sequences process. If you include a continue clause in the route-map sequence, the next route-map sequence
also processes after a match is found.
The S5148F-ON switch has the following limitations:
• ACL counter does not support byte count.
• ACL rule does not look up the next header for IPv6 packets.
• Layer 2 (L2) Egress ACL does not work for unknown unicast trac.
• L2 User ACL has a higher priority than the Layer 3 (L3) User ACL.
• You cannot modify or extend the hardware table for each ACL type.
• In IPv6 packets, only the protocol number of rst header is matched.
• The egress Deny ACL entry does not block soft-forwarded packets and CPU-originated ICMP packets.
IP ACLs
An ACL lters packets based on the:
• IP protocol number
• Source and destination IP address
• Source and destination TCP port number
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692 Access Control Lists