Dell S4048T, Configuration Manual

Page: 159 / 1277

Applying Egress Layer 3 ACLs (Control-Plane)
By default, packets originated from the system are not filtered by egress ACLs.
For example, if you initiate a ping session from the system and apply an egress ACL to block this type of traffic
on the interface, the ACL does not affect that ping traffic. The Control Plane Egress Layer 3 ACL feature
enhances IP reachability debugging by implementing control-plane ACLs for CPU-generated and 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.
NOTE: The
ip control-plane [egress filter]
and the
ipv6 control-plane [egress
filter]
commands are not supported.
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
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, 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:
Access Control Lists (ACLs) 159