Access Control List Commands

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Access Control List Commands
Access Control Lists (ACL) provide packet filtering for IP fram es (based on address,
protocol, Layer 4 protocol port number or TCP control code) or any frames (based
on MAC address or Ethernet type). To filter packets, first create an access list, ad d
the required rules and then bind the list to a specific port.
Access Control Lists
An ACL is a sequential list of permit or deny conditions that apply to IP addresses,
MAC addresses, or other more specific criteria. This switch tests ingres s or egress
packets against the conditions in an ACL one by one. A packet will be accepted as
soon as it matches a permit rule, or dropped as soon as it matc hes a deny rule. If no
rules match for a list of all permit rules, the packet is dropped; and if no rules match
for a list of all deny rules, the packet is accepted.
There are three filtering modes:
• Standard IP ACL m ode (STD-ACL) filters packets based on the sourc e IP address.
• Extended IP ACL mode (EXT-ACL) filters packets based on source or desti nation
IP address, as well as protocol type and protocol port number. If the TCP protocol
is specified, then you can also filter packets based on the TCP control code.
• MAC ACL mode (MAC- ACL) filters packets based on the source or destination
MAC address and the Ethernet frame type (RFC 1060).
The following restrictions apply to ACLs:
• Each ACL can have up to 32 rules.
• The maximum number of ACLs is 88.
• However, due to resour ce restrictions, the average number of rules bound the
ports should not exceed 20.
• This switch supports ACL s for ingress filtering only. However, you can only bind
one IP ACL to any port and one MAC ACL globally for ingress filtering. In other
words, only two ACLs can be bound to an interface - Ingress IP ACL and Ingress
MAC ACL.
The order in which active ACLs are checked is as follows:
1.U ser-defined rules in the Ingress MAC ACL for ingress ports.
2.User-defined rules in the Ingress IP ACL for ingress ports.
3.Exp licit default rule (permit any any) in the ingress IP ACL for ingress ports.
4.Exp licit default rule (permit any any) in the ingress MAC ACL for ingress ports.
5.If no explicit rule is matched, the implicit default is permit all.