This blog was originally started to better help me understand the technologies in the CCIE R&S blueprint; after completing the R&S track I have decided to transition the blog into a technology blog.

CCIE #29033

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Sunday, April 25, 2010

Question 27

How can I prevent ARP based attacks?

1 comments:

Packets Analyzed said...

DAI - Dynamic ARP inspection is a security features that validates the MAC to IP address using the DHCP snooping database. The packet will only be permitted once this validation occurs. If the validation fails the packet is dropped.

Must enable DHCP Snooping

To enable it per VLAN when using DHCP (global config)
"ip arp inspection vlan (#,#,#)"

To trust an interface and bypass the validation process.
interface fas 0/10
"ip arp inspection trust"

To enable DAI without DHCP - There is no DHCP binding database.

Create an arp access-list
"arp access-list ARP"
"permit ip host 10.1.1.2 mac host 1111.2222.3333"

Eanble inspection per VLAN
"ip arp inspection filter ARP vlan 10"

interface gig 0/1
"no ip arp inspection trust"

You can also rate limit the number of incoming arp packets
"ip arp inspection limit"

ARP validation checks do some extra validation against destination IP and/or mac
"ip arp inspection validate (src-mac|dst-mac|ip)"

"show ip arp inspection statistics"

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