Concept Guide

Conguring Filters Without a Sequence Number
If you are creating an extended ACL with only one or two lters, you can let Dell EMC Networking OS assign a sequence number based on
the order in which the lters are congured. Dell EMC Networking OS assigns lters in multiples of ve.
To congure a lter for an extended IP ACL without a specied sequence number, use any or all of the following commands:
• Congure a deny or permit lter to examine IP packets.
CONFIG-EXT-NACL mode
{deny | permit} {source mask | any | host ip-address} [count [byte]] [order] [monitor
[session-id]] [fragments]
• Congure a deny or permit lter to examine TCP packets.
CONFIG-EXT-NACL mode
{deny | permit} tcp {source mask] | any | host ip-address}} [count [byte]] [order] [monitor
[session-id]] [fragments]
• Congure a deny or permit lter 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 lters were assigned sequence numbers based on the order in which
they were congured (for example, the rst lter was given the lowest sequence number). The show config command in IP ACCESS
LIST mode displays the two lters with the sequence numbers 5 and 10.
Example of Viewing Filter Sequence for a Specied 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 congured 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 rst example in Congure a Standard IP ACL Filter.
Congure Layer 2 and Layer 3 ACLs
Both Layer 2 and Layer 3 ACLs may be congured 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 ltered against an L2 ACL.
• When Dell EMC Networking OS switches the packets, rst the L3 ACL lters them, then the L2 ACL lters them.
• When Dell EMC Networking OS switches the packets, the egress L3 ACL lters the packet.
For the following features, if you enable counters on rules that have already been congured 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)
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