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20-2
Cisco Nexus 1000V Troubleshooting Guide, Release 5.2(1)SV3(1.1)
OL-31593-01
Chapter 20 DHCP, DAI, and IPSG
Information About Dynamic ARP Inspection
Information About Dynamic ARP Inspection
Dynamic ARP Instpection (DAI) is used to validate ARP requests and responses as follows:
•
Intercepts all ARP requests and responses on untrusted ports.
•
Verifies that a packet has a valid IP-to-MAC address binding before updating the ARP cache or
forwarding the packet.
•
Drops invalid ARP packets.
DAI can determine the validity of an ARP packet based on valid IP-to-MAC address bindings stored in
a Dynamic Host Configuration Protocol (DHCP) snooping binding database. This database is built by
DHCP snooping when it is enabled on the VLANs and on the device. It might also contain static entries
that you have created.
For detailed information about configuring DAI, see the
Cisco Nexus 1000V Security Configuration
Guide
.
Information About IP Source Guard
IP Source Guard is a per-interface traffic filter that permits IP traffic only when the IP address and MAC
address of each packet matches the IP and MAC address bindings of dynamic or static IP source entries
in the Dynamic Host Configuration Protocol (DHCP) snooping binding table.
For detailed information about configuring IP Source Guard, see the
Cisco Nexus 1000V Security
Configuration Guide
.
Guidelines and Limitations for Troubleshooting
The following guidelines and limitations apply when troubleshooting DHCP snooping, Dynamic ARP
Inspection, or IP Source Guard:
•
A maximum of 12,000 DHCP entries can be snooped and learned system-wide in the DVS. This
combined total is for both entries learned dynamically and entries configured statically.
•
Rate limits on interfaces must be set to high values for trusted interfaces such as VSD SVM ports
or vEthernet ports that connect to DHCP servers.
•
Rate limits for trusted interfaces will be ignored.
•
A maximum of 2000 DHCP entries per host can be learned dynamically and configured statically.
•
A maximum of 1000 static DHCP entries per interface can be configured.
For detailed guidelines and limitations used in configuring these features, see the
Cisco Nexus 1000V
Security Configuration Guide
.