Dell PowerSwitch S4820T Configuration Guide for the S4820T System 9.14.1.0 - Page 121

Configuring Filters Without a Sequence Number, Con Layer 2 and Layer 3 ACLs

Page 121 highlights

Configuring Filters Without a Sequence Number If you are creating an extended ACL with only one or two filters, you can let Dell EMC Networking OS assign a sequence number based on the order in which the filters are configured. Dell EMC Networking OS assigns filters in multiples of five. To configure a filter for an extended IP ACL without a specified sequence number, use any or all of the following commands: • Configure a deny or permit filter to examine IP packets. CONFIG-EXT-NACL mode {deny | permit} {source mask | any | host ip-address} [count [byte]] [order] [monitor [session-id]] [fragments] • Configure a deny or permit filter to examine TCP packets. CONFIG-EXT-NACL mode {deny | permit} tcp {source mask] | any | host ip-address}} [count [byte]] [order] [monitor [session-id]] [fragments] • Configure a deny or permit filter to examine UDP packets. CONFIG-EXT-NACL mode {deny | permit} udp {source mask | any | host ip-address}} [count [byte]] [order] [monitor [session-id]] [fragments] When you use the log keyword, the CP logs details about the packets that match. Depending on how many packets match the log entry and at what rate, the CP may become busy as it has to log these packets' details. The following example shows an extended IP ACL in which the sequence numbers were assigned by the software. The filters were assigned sequence numbers based on the order in which they were configured (for example, the first filter was given the lowest sequence number). The show config command in IP ACCESS LIST mode displays the two filters with the sequence numbers 5 and 10. Example of Viewing Filter Sequence for a Specified Extended ACL DellEMC(config-ext-nacl)#deny tcp host 123.55.34.0 any DellEMC(config-ext-nacl)#permit udp 154.44.123.34 0.0.255.255 host 34.6.0.0 monitor 111 DellEMC(config-ext-nacl)#show config ! ip access-list extended nimule seq 5 deny tcp host 123.55.34.0 any seq 10 permit udp 154.44.0.0 0.0.255.255 host 34.6.0.0 monitor 111 DellEMC(config-ext-nacl)# To view all configured IP ACLs and the number of packets processed through the ACL, use the show ip accounting access-list command in EXEC Privilege mode, as shown in the first example in Configure a Standard IP ACL Filter. Configure Layer 2 and Layer 3 ACLs Both Layer 2 and Layer 3 ACLs may be configured on an interface in Layer 2 mode. If both L2 and L3 ACLs are applied to an interface, the following rules apply: • When Dell EMC Networking OS routes the packets, only the L3 ACL governs them because they are not filtered against an L2 ACL. • When Dell EMC Networking OS switches the packets, first the L3 ACL filters them, then the L2 ACL filters them. • When Dell EMC Networking OS switches the packets, the egress L3 ACL filters the packet. For the following features, if you enable counters on rules that have already been configured and a new rule is either inserted or prepended, all the existing counters are reset: • L2 ingress access list • L3 egress access list Access Control Lists (ACLs) 121

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Configuring
Filters Without a Sequence Number
If you are creating an extended ACL with only one or two
filters,
you can let Dell EMC Networking OS assign a sequence number based on
the order in which the
filters
are
configured.
Dell EMC Networking OS assigns
filters
in multiples of
five.
To
configure
a
filter
for an extended IP ACL without a
specified
sequence number, use any or all of the following commands:
Configure
a deny or permit
filter
to examine IP packets.
CONFIG-EXT-NACL mode
{deny | permit} {
source mask
| any | host
ip-address
} [count [byte]] [order] [monitor
[
session-id
]] [fragments]
Configure
a deny or permit
filter
to examine TCP packets.
CONFIG-EXT-NACL mode
{deny | permit} tcp {
source mask
] | any | host
ip-address
}} [count [byte]] [order] [monitor
[
session-id
]] [fragments]
Configure
a deny or permit
filter
to examine UDP packets.
CONFIG-EXT-NACL mode
{deny | permit} udp {
source mask
| any | host
ip-address
}} [count [byte]] [order] [monitor
[
session-id
]] [fragments]
When you use the
log
keyword, the CP logs details about the packets that match. Depending on how many packets match the log entry
and at what rate, the CP may become busy as it has to log these packets’ details. The following example shows an extended IP ACL in
which the sequence numbers were assigned by the software. The
filters
were assigned sequence numbers based on the order in which
they were
configured
(for example, the
first
filter
was given the lowest sequence number). The
show config
command in IP ACCESS
LIST mode displays the two
filters
with the sequence numbers 5 and 10.
Example of Viewing Filter Sequence for a
Specified
Extended ACL
DellEMC(config-ext-nacl)#deny tcp host 123.55.34.0 any
DellEMC(config-ext-nacl)#permit udp 154.44.123.34 0.0.255.255 host 34.6.0.0 monitor 111
DellEMC(config-ext-nacl)#show config
!
ip access-list extended nimule
seq 5 deny tcp host 123.55.34.0 any
seq 10 permit udp 154.44.0.0 0.0.255.255 host 34.6.0.0 monitor 111
DellEMC(config-ext-nacl)#
To view all
configured
IP ACLs and the number of packets processed through the ACL, use the
show ip accounting access-list
command in EXEC Privilege mode, as shown in the
first
example in
Configure
a Standard IP ACL Filter
.
Configure
Layer 2 and Layer 3 ACLs
Both Layer 2 and Layer 3 ACLs may be
configured
on an interface in Layer 2 mode.
If both L2 and L3 ACLs are applied to an interface, the following rules apply:
When Dell EMC Networking OS routes the packets, only the L3 ACL governs them because they are not
filtered
against an L2 ACL.
When Dell EMC Networking OS switches the packets,
first
the L3 ACL
filters
them, then the L2 ACL
filters
them.
When Dell EMC Networking OS switches the packets, the egress L3 ACL
filters
the packet.
For the following features, if you enable counters on rules that have already been
configured
and a new rule is either inserted or prepended,
all the existing counters are reset:
L2 ingress access list
L3 egress access list
Access Control Lists (ACLs)
121