Brocade Communications Systems 6650 manual Dynamic ARP inspection, ARP poisoning

	Chapter
DHCP	12

Table 69 lists the Dynamic Host Configuration Protocol (DHCP) packet inspection and tracking features supported in Brocade ICX 6650. These features are supported in the Layer 2, base Layer 3, edge Layer 3, and full Layer 3 software images, except where explicitly noted.

TABLE 69	Supported DHCP packet inspection and tracking features
Feature		Brocade ICX 6650
Dynamic ARP inspection		Yes
DHCP snooping		Yes
DHCP relay agent information (DHCP		Yes
Option 82)
IP source guard		Yes

Dynamic ARP inspection

For enhanced network security, you can configure the Brocade device to inspect and keep track of Dynamic Host Configuration Protocol (DHCP) assignments.

Dynamic ARP Inspection (DAI) enables the Brocade device to intercept and examine all ARP request and response packets in a subnet and discard those packets with invalid IP to MAC address bindings. DAI can prevent common man-in-the-middle (MiM) attacks such as ARP cache poisoning, and disallow mis-configuration of client IP addresses.

ARP poisoning

ARP provides IP communication within a Layer 2 broadcast domain by mapping an IP address to a MAC address. Before a host can talk to another host, it must map the IP address to a MAC address first. If the host does not have the mapping in its ARP table, it creates an ARP request to resolve the mapping. All computers on the subnet will receive and process the ARP requests, and the host whose IP address matches the IP address in the request will send an ARP reply.

An ARP poisoning attack can target hosts, switches, and routers connected to the Layer 2 network by poisoning the ARP caches of systems connected to the subnet and by intercepting traffic intended for other hosts on the subnet. For instance, a malicious host can reply to an ARP request with its own MAC address, thereby causing other hosts on the same subnet to store this information in their ARP tables or replace the existing ARP entry. Furthermore, a host can send gratuitous replies without having received any ARP requests. A malicious host can also send out ARP packets claiming to have an IP address that actually belongs to another host (e.g. the default router). After the attack, all traffic from the device under attack flows through the attacker computer and then to the router, switch, or host.

Brocade ICX 6650 Security Configuration Guide	279
53-1002601-01