Concept Guide

ACL Resequencing
ACL resequencing allows you to re-number the rules and remarks in an access or prex list.
The placement of rules within the list is critical because packets are matched against rules in sequential order. To order new rules using the
current numbering scheme, use resequencing whenever there is no opportunity.
For example, the following table contains some rules that are numbered in increments of 1. You cannot place new rules between these
packets, so apply resequencing to create numbering space, as shown in the second table. In the same example, apply resequencing if more
than two rules must be placed between rules 7 and 10.
You can resequence IPv4 and IPv6 ACLs, prexes, and MAC ACLs. No CAM writes happen as a result of resequencing, so there is no
packet loss; the behavior is similar Hot-lock ACLs.
NOTE: ACL resequencing does not aect the rules, remarks, or order in which they are applied. Resequencing merely renumbers
the rules so that you can place new rules within the list as needed.
Table 8. ACL Resequencing
Rules Resquencing
Rules Before Resequencing: seq 5 permit any host 1.1.1.1
seq 6 permit any host 1.1.1.2
seq 7 permit any host 1.1.1.3
seq 10 permit any host 1.1.1.4
Rules After Resequencing: seq 5 permit any host 1.1.1.1
seq 10 permit any host 1.1.1.2
seq 15 permit any host 1.1.1.3
seq 20 permit any host 1.1.1.4
Resequencing an ACL or Prex List
Resequencing is available for IPv4 and IPv6 ACLs, prex lists, and MAC ACLs.
To resequence an ACL or prex list, use the following commands. You must specify the list name, starting number, and increment when
using these commands.
• IPv4, IPv6, or MAC ACL
EXEC mode
resequence access-list {ipv4 | ipv6 | mac} {access-list-name StartingSeqNum Step-to-Increment}
• IPv4 or IPv6 prex-list
EXEC mode
resequence prefix-list {ipv4 | ipv6} {prefix-list-name StartingSeqNum Step-to-Increment}
Examples of Resequencing ACLs When Remarks and Rules Have the Same Number or Dierent Numbers
Remarks and rules that originally have the same sequence number have the same sequence number after you apply the resequence
command.
The example shows the resequencing of an IPv4 access-list beginning with the number 2 and incrementing by 2.
DellEMC(config-ext-nacl)# show config
!
142
Access Control Lists (ACLs)