HP PROCURVE 2910AL, Access Security Manual

Page: 405 / 594

Configuring Advanced Threat Protection
Dynamic ARP Protection
Enabling Dynamic ARP Protection
To enable dynamic ARP protection for VLAN traffic on a routing switch, enter
the
arp protect vlan
command at the global configuration level.
Syntax: [no] arp protect vlan [ vlan-range ]
vlan-range Specifies a VLAN ID or a range of VLAN IDs from
one to 4094; for example, 1–200.
An example of the arp protect vlan command is shown here:
ProCurve(config)# arp protect vlan 1-101
Configuring Trusted Ports
In a similar way to DHCP snooping, dynamic ARP protection allows you to
configure VLAN interfaces in two categories: trusted and untrusted ports. ARP
packets received on trusted ports are forwarded without validation.
By default, all ports on a switch are untrusted. If a VLAN interface is untrusted:
■
The switch intercepts all ARP requests and responses on the port.
■ Each intercepted packet is checked to see if its IP-to-MAC binding is valid.
If a binding is invalid, the switch drops the packet.
You must configure trusted ports carefully. For example, in the topology in
Figure 10-9, Switch B may not see the leased IP address that Host 1 receives
from the DHCP server. If the port on Switch B that is connected to Switch A
is untrusted and if Switch B has dynamic ARP protection enabled, it will see
ARP packets from Host 1 as invalid, resulting in a loss of connectivity.
On the other hand, if Switch A does not support dynamic ARP protection and
you configure the port on Switch B connected to Switch A as trusted, Switch B
opens itself to possible ARP poisoning from hosts attached to Switch A.
10-17