Access Control Lists (ACLs) for the Series 3400cl and Series 6400cl Switches 
Configuring and Assigning an ACL 
■  Duplicate ACEs are allowed in an ACL. However, multiple instances 
of an ACE have no effect on filtering because the first instance 
preempts any subsequent duplicates. Also, duplicate entries unnec-
essarily consume additional resources on assigned ACLs. 
For more information, refer to “Editing ACLs and Creating an ACL Offline” on 
page 10-65. 
Using CIDR Notation To Enter the ACL Mask 
You can use CIDR (Classless Inter-Domain Routing) notation to enter ACL 
masks. The switch interprets the bits specified with CIDR notation as the IP 
address bits in an ACL and the corresponding IP address bits in a packet. The 
switch then converts the mask to inverse notation for ACL use. 
Table 10-8.  Examples of CIDR Notation for Masks 
IP Address Used In an ACL 
with CIDR Notation 
Resulting ACL Mask  Meaning 
18.38.240.125/15  0.1.255.255  The leftmost 15 bits must match; the 
remaining bits are wildcards. 
18.38.240.125/20  0.0.15.255  The leftmost 20 bits must match; the 
remaining bits are wildcards. 
18.38.240.125/21  0.0.7.255  The leftmost 21 bits must match; the 
remaining bits are wildcards. 
18.38.240.125/24  0.0.0.255  The leftmost 24 bits must match; the 
remaining bits are wildcards. 
18.38.240.125/32  0.0.0.0  All bits must match. 
10-42