Using ACL Filters 55
Chapter5: Quality of Service
Understanding ACL Priority
Each ACL has a unique priority value, based on its number. The lower the ACL
number, the higher the priority, so ACL 1 has the highest priority.
The priority value is used to decide which ACL rule to apply when a packet matches
one or more ACLs. When an incoming packet matches the highest priority ACL, the
ACL’s configured action takes place. The other assigned ACLs are considered in
numeric order, from lowest to highest.
In the following example, the switch considers ACL 128 before ACL 130 because
ACL 128 has a higher priority. The order in which the ACLs are assigned to a port
does not affect their priority.
Port 1 access group
ACL IP Extended 128:
TCP
Port number = 80
Action = permit
ACL IP Extended 129:
TCP
Port number = 23
Action = deny
ACL IP Extended 130:
TCP
Port number = less than 100
Action = permit
Table 13: Well-Known Application Ports
Number
TCP/UDP
Application Number
TCP/UDP
Application Number
TCP/UDP
Application
20
21
22
23
25
37
42
43
53
69
70
ftp-data
ftp
ssh
telnet
smtp
time
name
whois
domain
tftp
gopher
79
80
109
110
111
119
123
143
144
161
162
finger
http
pop2
pop3
sunrpc
nntp
ntp
imap
news
snmp
snmptrap
179
194
220
389
443
520
554
1645, 1812
1813
1985
bgp
irc
imap3
ldap
https
rip
rtsp
RADIUS
RADIUS accounting
hsrp