Dell S4048T-ON, Configuration Manual

Page: 311 / 1146

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 ExaScale 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 L2Pr 13 additional L2Pr 15 L2Syst 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 Age(min) Hardware Address Interface VLAN CPU
---------------------------------------------------------------------
Internet 10.1.1.251 - 00:00:4d:57:f2:50 Te 1/2 Vl 10 CP
Internet 10.1.1.252 - 00:00:4d:57:e6:f6 Te 1/1 Vl 10 CP
Internet 10.1.1.253 - 00:00:4d:57:f8:e8 Te 1/3 Vl 10 CP
Internet 10.1.1.254 - 00:00:4d:69:e8:f2 Te 1/5 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.
Dynamic Host Configuration Protocol (DHCP) 311