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NOTE:
Dynamic ARP inspection (DAI) uses entries in the L2SysFlow CAM region, a sub-region of
SystemFlow. One CAM entry is required for every DAI-enabled VLAN. You can enable DAI on up to 16
VLANs on a system. However, the default CAM profile allocates only nine entries to the L2SysFlow region
for DAI. You can configure 10 to 16 DAI-enabled VLANs by allocating more CAM space to the L2SysFlow
region before enabling DAI.
SystemFlow has 102 entries by default. This region is comprised of two sub-regions: L2Protocol and
L2SystemFlow. L2Protocol has 87 entries; L2SystemFlow has 15 entries. Six L2SystemFlow entries are used
by Layer 2 protocols, leaving 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
Examples of Viewing the ARP Information
To view entries in the ARP database, use the show arp inspection database command.
Dell#show arp inspection database
Protocol
Address
---------------------------------------------------------------------
Internet
10.1.1.251
Internet
10.1.1.252
Internet
10.1.1.253
Internet
10.1.1.254
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
Age(min) Hardware Address
-
00:00:4d:57:f2:50
-
00:00:4d:57:e6:f6
-
00:00:4d:57:f8:e8
-
00:00:4d:69:e8:f2
: 0
Interface VLAN
Te 0/2
Te 0/1
Te 0/3
Te 0/50
Dynamic Host Configuration Protocol (DHCP)
CPU
Vl 10
CP
Vl 10
CP
Vl 10
CP
Vl 10
CP
408
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Troubleshooting
