HP ProCurve 6120G/XG Manual page 340

IPv4 Access Control Lists (ACLs)
ACL Operation
2.
3.
4.
The following ACL model, when assigned to inbound filtering on port 12,
supports the above case:
1
2
3
4
5
1. Permits IP traffic inbound from source address 11.11.11.42.
Packets matching this criterion are permitted and will not be
compared to any later ACE in the list. Packets not matching this
criterion will be compared to the next entry in the list.
2. Denies Telnet traffic from source address 11.11.11.101. Packets
matching this criterion are dropped and are not compared to
later criteria in the list. Packets not matching this criterion are
compared to the next entry in the list.
3. Permits any IP traffic from source address 11.11.11.101. Any
packets matching this criterion will be permitted and will not be
compared to any later criteria in the list. Because this entry
comes after the entry blocking Telnet traffic from this same
address, there will not be any Telnet packets to compare with
this entry; they have already been dropped as a result of
matching the preceding entry.
Figure 9-4. Example of How an ACL Filters Packets
It is important to remember that this ACL (and all ACLs) include an implicit
deny any. That is, inbound IP packets (including switched packets having the
switch as the destination IP address) that the ACL does not explicitly permit
or deny will be implicitly denied, and therefore dropped. You can preempt
the implicit deny by inserting a "permit IP any" at the end of an ACL, but this
solution does not apply in the preceding example, where the intention is for
the switch to allow only explicitly permitted packets inbound on port 12.
9-16
Deny only the inbound Telnet traffic sent from IP address 11.11.11.101.
Permit only inbound Telnet traffic sent from IP address 11.11.11.33.
Deny all other inbound traffic on port 12.
4. Permits Telnet traffic from source address 11.11.11.33. Packets
matching this criterion are permitted and are not compared to
any later criteria in the list. Packets not matching this criterion
are compared to the next entry in the list.
5. This entry does not appear in an actual ACL, but is implicit as
the last entry in every ACL. Any inbound packets on port 12 that
do not match any of the criteria in the ACL's preceding entries
will be denied (dropped).