Dell PowerSwitch S4820T Configuration Guide for the S4820T System 9.14.1.0 - Page 316
Configuring Dynamic ARP Inspection, dynamic ARP inspection-limit
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Broadcast MAC flooding Denial of service An attacker can broadcast an ARP reply that specifies FF:FF:FF:FF:FF:FF as the gateway's MAC address, resulting in all clients broadcasting all internet-bound packets. An attacker can send fraudulent ARP messages to the gateway until the ARP cache is exhausted, after which, traffic from the gateway is broadcast. An attacker can send a fraudulent ARP messages to a client to associate a false MAC address with the gateway address, which would blackhole all internet-bound packets from the client. 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. 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. DellEMC#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 DellEMC# To see how many valid and invalid ARP packets have been processed, use the show arp inspection statistics command. DellEMC#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 DellEMC# Configuring dynamic ARP inspection-limit To configure dynamic ARP inspection rate limit on a port, perform the following task. 1 Enter into global configuration mode. EXEC Privilege mode configure terminal 2 Select the interface to be configured. CONFIGURATION mode 316 Dynamic Host Configuration Protocol (DHCP)
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