Dell S3048-ON, Руководство по настройке

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If counters are enabled on ACL rules that are already configured, those counters are reset when a new rule which is inserted or prepended
or appended requires a hardware shift in the flow table. Resetting the counters to 0 is transient as the proginal counter values are retained
after a few seconds. If there is no need to shift the flow in the hardware, the counters are not affected. This is applicable to the following
features:
• L2 Ingress Access list
• L2 Egress Access list
NOTE: IP ACLs are supported over VLANs in Dell Networking OS version 6.2.1.1 and higher.
Assigning ACLs to VLANs
When you apply an ACL to a VLAN using single port-pipe, a copy of the ACL entries gets installed in the ACL CAM on the port-pipe. The
entry looks for the incoming VLAN in the packet. When you apply an ACL on individual ports of a VLAN, separate copies of the ACL entries
are installed for each port belonging to a port-pipe.
You can use the
log
keyword to log the details about the packets that match. The control processor becomes busy based on the number
of packets that match the log entry and the rate at which the details are logged in. However, the route processor (RP) is unaffected. You
can use this option for debugging issues related to control traffic.
ACL Optimization
If an access list contains duplicate entries, Dell Networking OS deletes one entry to conserve CAM space.
Standard and extended ACLs take up the same amount of CAM space. A single ACL rule uses two CAM entries to identify whether the
access list is a standard or extended ACL.
Determine the Order in which ACLs are Used to Classify Traffic
When you link class-maps to queues using the
service-queue
command, Dell Networking OS matches the class-maps according to
queue priority (queue numbers closer to 0 have lower priorities).
As shown in the following example, class-map cmap2 is matched against ingress packets before cmap1 .
ACLs acl1 and acl2 have overlapping rules because the address range 20.1.1.0/24 is within 20.0.0.0/8. Therefore (without the keyword
order), packets within the range 20.1.1.0/24 match positive against cmap1 and are buffered in queue 7, though you intended for these
packets to match positive against cmap2 and be buffered in queue 4.
In cases where class-maps with overlapping ACL rules are applied to different queues, use the
order
keyword to specify the order in
which you want to apply ACL rules. The order can range from 0 to 254. Dell Networking OS writes to the CAM ACL rules with lower-order
numbers (order numbers closer to 0) before rules with higher-order numbers so that packets are matched as you intended. By default, all
ACL rules have an order of
255 .
Example of the
order
Keyword to Determine ACL Sequence
Dell(conf)#ip access-list standard acl1
Dell(config-std-nacl)#permit 20.0.0.0/8
Dell(config-std-nacl)#exit
Dell(conf)#ip access-list standard acl2
Dell(config-std-nacl)#permit 20.1.1.0/24 order 0
Dell(config-std-nacl)#exit
Dell(conf)#class-map match-all cmap1
Dell(conf-class-map)#match ip access-group acl1
Dell(conf-class-map)#exit
Dell(conf)#class-map match-all cmap2
Dell(conf-class-map)#match ip access-group acl2
Dell(conf-class-map)#exit
Dell(conf)#policy-map-input pmap
Dell(conf-policy-map-in)#service-queue 7 class-map cmap1
110 Access Control Lists (ACLs)