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NOTE: When assigning sequence numbers to filters, you may have to insert a new filter. To prevent reconfiguring multiple
filters, assign sequence numbers in multiples of five or another number.
The example below shows how the seq command orders the filters according to the sequence number assigned. In the example,
filter 15 was configured before filter 5, but the show config command displays the filters in the correct order.
DellEMC(config-ext-nacl)#seq 15 deny ip host 112.45.0.0 any log monitor 501
DellEMC(config-ext-nacl)#seq 5 permit tcp 12.1.3.45 0.0.255.255 any
DellEMC(config-ext-nacl)#show config
!
ip access-list extended dilling
seq 5 permit tcp 12.1.0.0 0.0.255.255 any
seq 15 deny ip host 112.45.0.0 any log monitor 501
DellEMC(config-ext-nacl)#
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.
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.
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Access Control Lists (ACLs)