Users Guide

CAM Optimization
When you enable this command, if a policy map containing classication rules (ACL and/or dscp/ ip-precedence rules) is applied to
more than one physical interface on the same port-pipe, only a single copy of the policy is written (only one FP entry is used). When
you disable this command, the system behaves as described in this chapter.
Test CAM Usage
This command applies to both IPv4 and IPv6 CAM proles, but is best used when verifying QoS optimization for IPv6 ACLs.
To determine whether sucient ACL CAM space is available to enable a service-policy, use this command. To verify the actual CAM
space required, create a class map with all the required ACL rules, then execute the test cam-usage command in Privilege mode.
The following example shows the output when executing this command. The status column indicates whether you can enable the
policy.
Example of the test cam-usage Command
Dell#test cam-usage service-policy input asd stack-unit 1 port-set 0
Stack-unit|Portpipe|CAM Partition|Available CAM|Estimated CAM per Port|Status
--------------------------------------------------------------------------
1| 1| IPv4Flow| 232| 0|Allowed
Dell#
Implementing ACLs on Dell Networking OS
You can assign one IP ACL per interface with Dell Networking OS. If you do not assign an IP ACL to an interface, it is not used by the
software in any other capacity.
The number of entries allowed per ACL is hardware-dependent. For detailed specication on entries allowed per ACL, refer to your
line card documentation.
If counters are enabled on ACL rules that are already congured, those counters are reset when a new rule which is inserted or
prepended or appended requires a hardware shift in the ow 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 ow in the hardware, the counters are not disturbed. 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.
ACLs and VLANs
There are some dierences when assigning ACLs to a VLAN rather than a physical port.
For example, when using a single port-pipe, if you apply an ACL to a VLAN, one copy of the ACL entries is installed in the ACL CAM
on the port-pipe. The entry looks for the incoming VLAN in the packet. Whereas if 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.
When you use the log keyword, the CP has to log the details about the packets that match. Depending on how many packets
match the log entry and at what rate, the CP might become busy as it has to log these packets’ details. However, the other
processors (RP1 and RP2) are unaected. This option is typically useful when debugging some problem related to control trac. We
have used this option numerous times in the eld and have not encountered problems so far.
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 whether it is
identied as a standard or extended ACL.
Access Control Lists (ACLs)
113