CPU-forwarded traffic. Using permit rules with the count option, you can track on a per-flow basis
whether CPU-generated and CPU-forwarded packets were transmitted successfully.
1. Apply Egress ACLs to IPv4 system traffic.
CONFIGURATION mode
ip control-plane [egress filter]
2. Create a Layer 3 ACL using permit rules with the count option to describe the desired CPU traffic.
CONFIG-NACL mode
permit ip {source mask | any | host ip-address} {destination mask | any |
host ip-address} count
Dell Networking OS Behavior: Virtual router redundancy protocol (VRRP) hellos and internet group
management protocol (IGMP) packets are not affected when you enable egress ACL filtering for CPU
traffic. Packets sent by the CPU with the source address as the VRRP virtual IP address have the interface
MAC address instead of VRRP virtual MAC address.
IP Prefix Lists
IP prefix lists control routing policy.
An IP prefix list is a series of sequential filters that contain a matching criterion (examine IP route prefix)
and an action (permit or deny) to process routes. The filters are processed in sequence so that if a route
prefix does not match the criterion in the first filter, the second filter (if configured) is applied. When the
route prefix matches a filter, the system drops or forwards the packet based on the filter’s designated
action. If the route prefix does not match any of the filters in the prefix list, the route is dropped (that is,
implicit deny).
A route prefix is an IP address pattern that matches on bits within the IP address. The format of a route
prefix is A.B.C.D/X where A.B.C.D is a dotted-decimal address and /X is the number of bits that should be
matched of the dotted decimal address. For example, in 112.24.0.0/16, the first 16 bits of the address
112.24.0.0 match all addresses between 112.24.0.0 to 112.24.255.255.
The following examples show permit or deny filters for specific routes using the le and ge parameters,
where x.x.x.x/x represents a route prefix:
• To deny only /8 prefixes, enter deny x.x.x.x/x ge 8 le 8.
• To permit routes with the mask greater than /8 but less than /12, enter permit x.x.x.x/x ge 8.
• To deny routes with a mask less than /24, enter deny x.x.x.x/x le 24.
• To permit routes with a mask greater than /20, enter permit x.x.x.x/x ge 20.
The following rules apply to prefix lists:
• A prefix list without any permit or deny filters allows all routes.
• An “implicit deny” is assumed (that is, the route is dropped) for all route prefixes that do not match a
permit or deny filter in a configured prefix list.
• After a route matches a filter, the filter’s action is applied. No additional filters are applied to the route.
122 Access Control Lists (ACLs)