NETGEAR SRX5308 - ProSafe® Quad WAN Gigabit SSL VPN Firewall Reference Manual page 118

ProSafe Gigabit Quad WAN SSL VPN Firewall SRX5308 Reference Manual
Table 4-4. Attack Checks Settings (continued)
Setting
LAN Security Checks.
Block UDP flood
Disable Ping Reply
on LAN Ports
VPN Pass through
IPSec
PPTP
L2TP
4. Click Apply to save your settings.
4-28
Description (or Subfield and 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.
v1.0, April 2010
Firewall Protection