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Filters and QOS Configuration for Ethernet Routing Switch 5500
Technical Configuration Guide
33
January 2013
avaya.com
8.2 Dynamic ARP Inspection
Dynamic ARP Inspection verifies the ARP packets to prevent man -in-the-middle (MITM) types of attacks.
Without dynamic ARP inspection, a malicious user can attack hosts in a local subnet by poisoning the
ARP cache of hosts connected to this subnet by intercepting traffic intended for other hosts on the subnet.
This normally takes place on VLA N with multiple hosts connec ted. Dynamic ARP inspection is used
together with DHCP snooping by using the binding table to validate the host MAC address to IP address
binding on untrusted ports. ARP packets on untrusted ports are only forward if they match the source
MAC to IP address in the binding table. DHCP snooping must be enable prior to enabling dynamic ARP
inspection.
8.2.1 Dynamic ARP Inspection Configuration
Assuming DHCP snooping is already enable for VLANs 100 and 200 and port 1/19 is the uplink port,
enter the following commands:
5500(config)#
ip arp-inspection vlan 100
5500(config)#
ip arp-inspection vlan 200
5500(config)#
interface fastEthernet 1/24
5500(config-if)#
ip arp-inspection trusted
5500(config-if)#
exit
8.3 IP Source Guard
IP source guard works toget her with the DHCP snooping binding table by providing security against
invalid sourc e IP addresses. If enabled, the source IP address is checked against the source IP address
in the binding table on untrusted ports. If the incoming source IP address does not match the IP addre ss
in the binding table, the packet is dropped. Please note that manual (static) assignment of IP addresses is
not allowed as DHCP snooping does not support static binding entries
8.3.1 IP Source Guard Configuration
Assuming DHCP snooping is already configured with untrusted port members 2-20, enter the following
commands:
5500(config)#
interface fastEthernet
2-20
5500(config-if)#
ip verify source
5500(config-if)#
exit