Reference Guide

NOTE: The ip control-plane [egress filter] and the ipv6 control-plane [egress
filter] commands are not supported on the S4820T system.
1. Apply Egress ACLs to IPv4 system traffic.
CONFIGURATION mode
ip control-plane [egress filter]
2. Apply Egress ACLs to IPv6 system traffic.
CONFIGURATION mode
ipv6 control-plane [egress filter]
3. 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
FTOS 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
Prefix lists are supported on the S4820T platform.
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, Dell Networking OS 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.
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Access Control Lists (ACLs)