47-14
Software Configuration Guide—Release 15.0(2)SG
OL-23818-01
Chapter 47 Configuring Network Security with ACLs
TCAM Programming and ACLs for Supervisor Engine II-Plus, Supervisor Engine IV, Supervisor Engine V, and Supervisor
DHCP Snooping should be enabled globally on a given VLAN.
The following bullets only apply to supervisor engines other than 6-E and 6L-E.
Unicast Routing should be enabled and SVI (or a Layer 3 physical) interface should be up and
configured with an IP protocol address. it is because interfaces immediately become part of the
routing process once the SVI interface comes up and the protocol family address is configured.
Multicast Routing should be enabled and one of the multicast routing protocols should be configured
on the interface (IGMP, PIMv1, PIMv2, MBGP, MOSPF, DVMRP, and IGMP snooping).
Guidelines and Restrictions
Note Before configuring per-VLAN capture mode, you should examine your configuration to ensure that only
the necessary features are enabled on the desired VLANs.
The following guidelines and restrictions apply to per-VLAN capture mode:
Starting with Cisco IOS Release 15.0(2)SG, for Supervisor Engine 6-E and Supervisor Engine 6L-E,
globally reserved static ACL entries in the TCAM region for Layer 3 control packets are removed.
The per-VLAN CTI command is not needed and does not apply for Layer 3 control packets because
these packets are captured in per-VLAN fashion by default.
The following still function:
Global static capture and CTI commands for IGMP or PIM packets (both use MAC addresses
224.0.0.1 and 224.0.0.2)
Global and per-VLAN CTI for DHCP packets
With Cisco IOS Release 15.0(2)SG, per-VLAN capture of Layer 3 control packets is driven by SVI
configuration. Except for IGMP, PIM, or DHCP, no special configuration is required.
Enabling per-VLAN capture mode consumes additional entries in the ACL/feature TCAM.
The number of available TCAM entries depends on the type of supervisor engine. The entry and
mask count further limits the utilization of the ACL/feature TCAM.
Certain configurations can exhaust TCAM resource earlier in per-VLAN capture mode than in
global capture mode (such as, when IP Source Guard is enabled on several interfaces or on a
user-configured PACL).
You can resize TCAM regions to make more entries available to the PortAndVlan or PortOrVlan
region based on the configuration. This allows more entries to be programmed in hardware before
reaching the limit. When TCAM resources are exhausted, the packets are forwarded in software.
In per-VLAN capture mode, you can configure ACLs to permit or deny control traffic on a VLAN
or port.
Because security ACLs are terminated by an implicit deny, you must ensure that the ACLs are
configured to permit the control packets necessary for the feature (protocol) to operate. However,
this rule does not differ from the default behavior.