Dell Force10 MXL Blade MXL 10/40GbE Switch IO Module Configuration Guide - Page 75

ACLs and VLANs, ACL Optimization, Determine the Order in Which ACLs are Used to Classify Traffic

Page 75 highlights

• L3 Ingress Access list • L3 Egress Access list Note: IP ACLs are supported over VLANs in Version 6.2.1.1 and higher. V 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 gets 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 are installed for each port belonging to a port-pipe. ACL Optimization If an access list contains duplicate entries, FTOS deletes one of the entries 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 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 service-queue command, FTOS matches the class-maps according to queue priority (queue numbers closer to 0 have lower priorities). For example, in Figure 5-1, 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 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 (Figure 5-1). 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. Access Control Lists (ACLs) | 73

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Access Control Lists (ACLs)
|
73
L3 Ingress Access list
L3 Egress Access list
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 gets 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 are installed for
each port belonging to a port-pipe.
ACL Optimization
If an access list contains duplicate entries, FTOS deletes one of the entries 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 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
service-queue
command, FTOS matches the class-maps
according to queue priority (queue numbers closer to 0 have lower priorities). For example, in
Figure 5-1
,
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 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 (
Figure 5-1
). 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.
V
Note:
IP ACLs are supported over VLANs in Version 6.2.1.1 and higher.