Users Guide

Table Of Contents
692 Access Control Lists
PBR Associated ACLs and DiffServ Policies Processed After User-defined ACLs
Each ACL in an access-group is associated with a sequence number
indicating the order in which the ACL is processed by the hardware. Likewise,
a route-map may have multiple statements with different sequence numbers
associated with each ACL entry. These statements are processed in sequential
order after the implicit deny all at the end of the user-defined ACL and
beginning with the lowest numbered rule, but only after all user configured
ACLs that are not associated with any route-map.
Likewise, a DiffServ policy may have multiple statements, including match
criteria referring to an ACL. As a DiffServ policy may be configured on an
interface with an ACL, and vice-versa, the ACL statements are processed
first, then the ACL implicit deny all is processed, and then the DiffServ policy
match statements (including permit/deny statements in a referred ACL) and
actions are processed.
Implicitly, any packet that does not match a permit clause in an ACL is
dropped. Packets that do not match the match clauses in a PBR or DiffServ
Policy are processed in the normal manner and packets that match the PBR or
DiffServ Policy are processed per the policy.
ACL Resource Usage
When a route-map defines a “match” rule associated with an ACL, except for
the implicit routing behavior mentioned above, the resource consumption is
the same as if a normal ACL is applied on an interface. Rules consumed by an
ACL corresponding to route-map “match” clause share hardware resources
with the ACL component. Some resources cannot be shared. For example, it
is not permitted to utilize the rate-limit clause in a PBR ACL, as the hardware
cannot support both a counter (allocated by every PBR route-map) and a rate
limit.
ACLs associated with a route-map and general ACLs share the same hardware
resources. If PBR consumes the maximum number of hardware resources on
an interface/system wide, general purpose ACLs can't be configured later and
vice versa. Hardware allocation is performed on a first-come first-serve basis
when the interface becomes active.