FTOS Configuration Guide for the C-Series - Force10 Networks

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• L3 Egress Access list
Note: IP ACLs are supported over VLANs in Version 6.2.1.1 and higher.
ACLs and VLANs
There are some differences 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 would get
installed in the ACL CAM on the port-pipe. The entry would look 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 would be
installed for each port belonging to a port-pipe.
When you use the ‘log’ option, CP processor will have to log details about the packets that match.
Depending on how many packets match the ‘log’ entry and at what rate, CP might become busy as it has to
log these packets’ details. However the other processors (RP1 and RP2) should be unaffected. This option
is typically useful when debugging some problem related to control traffic. We have used this option
numerous times in the field and have not encountered any problems in such usage so far.
ACL Optimization
If an access list contains duplicate entries, FTOS deletes one entry to conserve CAM space.
Standard and Extended ACLs take up the same amount of CAM space. A single ACL rule uses 2 CAM
entries whether it is identified as 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 command service-queue, FTOS matches the class-maps
according to queue priority (queue numbers closer to 0 have lower priorities). For example, in Figure 225,
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 postive 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 such as these, 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, as shown in Figure 225. The
order can range from 0 to 254. FTOS 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 254.
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