Reference Guide
nine for DAI. L2Protocol can have a maximum of 100 entries; you must expand this region to capacity before you can
increase the size of L2SystemFlow. This is relevant when you are enabling DAI on VLANs. If, for example, you want to
enable DAI on 16 VLANs, you need seven more entries; in this case, reconfigure the SystemFlow region for 122 entries using
the layer-2 eg-acl value fib value frrp value ing-acl value learn value l2pt value qos
value system-flow 122 command.
The logic is as follows:
L2Protocol has 87 entries by default and must be expanded to its maximum capacity, 100 entries, before L2SystemFlow can
be increased; therefore, 13 more L2Protocol entries are required. L2SystemFlow has 15 entries by default, but only nine are
for DAI; to enable DAI on 16 VLANs, seven more entries are required. 87 L2Protocol + 13 additional L2Protocol + 15
L2SystemFlow + 7 additional L2SystemFlow equals 122.
Configuring Dynamic ARP Inspection
To enable dynamic ARP inspection, use the following commands.
1. Enable DHCP snooping.
2. Validate ARP frames against the DHCP snooping binding table.
INTERFACE VLAN mode
arp inspection
To view entries in the ARP database, use the show arp inspection database command.
Dell#show arp inspection database
Protocol Address Age(min) Hardware Address Interface VLAN CPU
---------------------------------------------------------------------
Internet 10.1.1.251 - 00:00:4d:57:f2:50 Te 0/2 Vl 10 CP
Internet 10.1.1.252 - 00:00:4d:57:e6:f6 Te 0/1 Vl 10 CP
Internet 10.1.1.253 - 00:00:4d:57:f8:e8 Te 0/3 Vl 10 CP
Internet 10.1.1.254 - 00:00:4d:69:e8:f2 Te 0/50 Vl 10 CP
Dell#
To see how many valid and invalid ARP packets have been processed, use the show arp inspection statistics
command.
Dell#show arp inspection statistics
Dynamic ARP Inspection (DAI) Statistics
---------------------------------------
Valid ARP Requests : 0
Valid ARP Replies : 1000
Invalid ARP Requests : 1000
Invalid ARP Replies : 0
Dell#
Bypassing the ARP Inspection
You can configure a port to skip ARP inspection by defining the interface as trusted, which is useful in multi-switch
environments.
ARPs received on trusted ports bypass validation against the binding table. All ports are untrusted by default.
To bypass the ARP inspection, use the following command.
● Specify an interface as trusted so that ARPs are not validated against the binding table.
INTERFACE mode
arp inspection-trust
DAI is supported on Layer 2 and Layer 3.
Dynamic Host Configuration Protocol (DHCP)
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