NETGEAR ProSafe SRX5308 Reference Manual page 108

ProSafe Gigabit Quad WAN SSL VPN Firewall SRX5308
Table 20. Attack Checks screen settings (continued)
Setting
LAN Security Checks.
Block UDP flood
Disable Ping Reply
on LAN Ports
VPN Pass through
IPSec
PPTP
L2TP
Multicast Pass through
Enable IGMP
Pass through
3. Click Apply to save your settings.
Description
Select the Block UDP flood check box to prevent the VPN firewall from accepting
more than 20 simultaneous, active UDP connections from a single device on the
LAN. By default, the Block UDP flood check box is cleared.
A UDP flood is a form of denial of service attack that can be initiated when one
device sends a large number of UDP packets to random ports on a remote host. As
a result, the distant host does the following:
1. Checks for the application listening at that port.
2. Sees that no application is listening at that port.
3. Replies with an ICMP Destination Unreachable packet.
When the victimized system is flooded, it is forced to send many ICMP packets,
eventually making it unreachable by other clients. The attacker might also spoof the
IP address of the UDP packets, ensuring that the excessive ICMP return packets do
not reach him, thus making the attacker's network location anonymous.
Select the Disable Ping Reply on LAN Ports check box to prevent the VPN firewall
from responding to a ping on a LAN port. A ping can be used as a diagnostic tool.
Keep this check box cleared unless you have a specific reason to prevent the VPN
firewall from responding to a ping on a LAN port.
When the VPN firewall functions in NAT mode, all packets going to the remote VPN
gateway are first filtered through NAT and then encrypted per the VPN policy. For
example, if a VPN client or gateway on the LAN side of the VPN firewall wants to
connect to another VPN endpoint on the WAN side (placing the VPN firewall
between two VPN endpoints), encrypted packets are sent to the VPN firewall.
Because the VPN firewall filters the encrypted packets through NAT, the packets
become invalid unless you enable the VPN Pass through feature.
To enable the VPN tunnel to pass the VPN traffic without any filtering, select any or
all of the following check boxes:
• IPSec. Disables NAT filtering for IPSec tunnels.
• PPTP. Disables NAT filtering for PPTP tunnels.
• L2TP. Disables NAT filtering for L2TP tunnels.
By default, all three check boxes are selected.
IP multicast pass-through allows multicast packets that originate in the WAN subnet,
such as packets from a media streaming or gaming application, to be forwarded to
the LAN subnet. Internet Group Management Protocol (IGMP) is used to support
multicast between IP hosts and their adjacent neighbors.
Select the Enable IGMP Pass through check box to enable IP multicast
pass-through. By default, IP multicast pass-through is enabled.
Firewall Protection
108