Packet Filtering, Incoming Interface, Action | SnapGear 2.0.1

Packet Filtering

By default, your CyberGuard SG appliance allows network traffic as shown in the following table:

Incoming Interface

LAN/VPN/Dial-In

DMZ

DMZ

WAN

Outgoing Interface

Any

WAN

Any except WAN

Any

Action

Accept

Accept

Drop

Drop

You can configure your CyberGuard SG appliance with additional filter rules to allow or restrict network traffic. These rules can match traffic based on the source and destination address, the incoming and outgoing network port, and/or the services.

You can also configure your CyberGuard SG appliance to perform network address translation (NAT). This may be in the form of source address NAT, destination address NAT, or 1-to-1 NAT. Network address translation modifies the IP address and/or port of traffic traversing the CyberGuard SG appliance.

The most common use of this is for port forwarding (aka PAT/Port Address Translation) from ports on the CyberGuard SG appliance’s WAN interface to ports on machines on the LAN. This is the most common way for internal, masqueraded servers to offer services to the outside world. Destination NAT rules are used for port forwarding.

Source NAT rules are useful for masquerading one or more IP addresses behind a single other IP address. This is the type of NAT used by the CyberGuard SG appliance to masquerade your private network behind its public IP address.

1-to-1 NAT creates both Destination NAT and Source NAT rules for full IP address translation in both directions. This can be useful if you have a range of IP addresses that have been added as interface aliases on the CyberGuard SG appliance’s WAN interface, and want to associate one of these external alias IP addresses with a single internal, masqueraded computer. This effectively allocates the internal computer its own real world IP address, also known as a virtual DMZ.

Function	NAT Method

Port forwarding (PAT)	Destination NAT

Masquerading	Source NAT

Virtual DMZ	1-to-1 NAT

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SnapGear 2.0.1 user manual Packet Filtering, Incoming Interface, Outgoing Interface, Action, Function NAT Method

Contents

Revision June 7 Contents 104 Firewall 169 159170 177 Introduction IntroductionCyberGuard SG Gateway Appliances CyberGuard SG PCI Appliances Secure by default Bridged mode Document Conventions Text like this highlights important issues SG300 model includes two blue straight through UTP cables Your CyberGuard SG Gateway ApplianceFront panel LEDs Rear panel Virtual Private Networking is enabled Internet link features CyberGuard SG Gateway Appliance FeaturesLAN link features DMZ link features SG570, SG575 only LEDs Your CyberGuard SG PCI Appliance Environmental features CyberGuard SG PCI Appliance FeaturesNetwork link features Getting Started 255.255.255.0 192.168.0.1Page Right click on Local Area Connection and select Properties 192.168.0.100 Set up the Password and LAN Connection Settings Root Getting Started Getting Started Cable modem Set up Internet Connection SettingsAnalog modem DSL modem Set up the PCs on your LAN to Access the Internet LAN with no Dhcp server LAN with a Dhcp server To manually set up each Windows PC on your network Select Dhcp Server from the Networking menu Getting Started Set up your PC to Connect to the Web Management Console Install the Network Driver on your PC Select Use the following DNS server addresses and enter Select Internet Protocol TCP/IP and click Properties Set up the Password and Network Connection Settings Network Setup Connections page will display Ensure Dhcp assigned is unchecked Click Apply and Reboot Getting Started Click Apply and Reboot Getting Started Page Network Connections Network ConnectionsConnections Bridging LAN Internet Cable Internet Connection MethodsPhysically connect modem device Direct Internet Bridged Internet Dialout Internet COM/ModemFailover Direct/Cable/ADSL Internet Optional ISP. The Password and Confirm Password fields mustField Description Bridged DMZ Dialin accessDirect DMZ Direct LAN Services on the DMZ NetworkBridged LAN DMZ as a second Internet connection Internet Failover DMZ as a backup/failover Internet connectionLoad Balancing Set up a secondary backup Internet connection Enable the primary connection for failover Network Connections Route management RoutesAdditional routes DNS Proxy AdvancedHostname Network Address Translation NAT/masquerading Dynamic DNS Interface aliases Change MAC address QoS Traffic Shaping Dialin Setup Dialin Setup Dialin Setup Following table describes the fields on the Dial-In Setup Dialin User Accounts Account list Page Windows 95/98/Me Remote User Configuration Dialin Setup Windows 2000/XP Dialin Setup Page Dhcp Server Dhcp Server ConfigurationDhcp Server Dhcp Server Subnet List Enable/DisableInterface Subnet Dhcp Server Dhcp Proxy Firewall Incoming AccessFirewall Administration services CyberGuard SG Administrative Web Server SSL/HTTPS Secure Http Add Local and Private Certificates SSL Certificate Setup Incoming Interface Packet FilteringOutgoing Interface Action Addresses Service groups Rules Descriptive Name EnableDestination NAT/port forwarding Source NAT Destination ServicesSource Address Destination Address To-1 NAT Rules User authentication Access Control and Content FilteringPage Click Advanced Browser setup IP lists Web lists Content Categories Reports ZoneAlarm Intrusion Detection Intrusion Detection Benefits of using an IDS Basic Intrusion Detection and Blocking Page Advanced Intrusion Detection Advanced Intrusion Detection configuration Intrusion Detection Setting up the analysis server Page Web Cache Web CacheWeb cache is only available on SG575 models Cache size Web Cache Setup 100 Web Cache Network SharesCreate a new user account 101 Web Cache Create the network share 102 Web Cache Set the CyberGuard SG appliance to use the network share 103 Web Cache Set up LAN PCs to Use the Web CachePeers 104 Virtual Private Networking Virtual Private Networking Pptp Client Setup 106 Virtual Private Networking 107 Virtual Private Networking Pptp Server Setup 108 Virtual Private Networking Enable and configure the Pptp VPN server 109 Virtual Private Networking Data private as well as providing secure authenticationEncryption is strongly recommended. This keeps your Configuring user accounts for VPN server 111 Virtual Private Networking 112 Virtual Private Networking Configuring the remote VPN client Windows 95, Windows 98 and Windows Me 114 Virtual Private Networking Windows 115 Virtual Private Networking 116 Virtual Private Networking Windows XP 117 Virtual Private Networking Connecting the remote VPN client Set up the Branch Office IPSec SetupCyberGuard SG appliance to CyberGuard SG appliance Enabling IPSec 119 Virtual Private Networking 120 Virtual Private Networking Configure a tunnel to connect to the headquarters officeTunnel settings 121 Virtual Private Networking 122 Virtual Private Networking 123 Virtual Private Networking Local endpoint settings 124 Virtual Private Networking 125 Virtual Private Networking Other options 126 Virtual Private Networking 127 Virtual Private Networking 128 Virtual Private Networking Tcgid 129 Virtual Private Networking Phase 1 settingsKept confidential 130 Virtual Private Networking 131 Virtual Private Networking Phase 2 settings 132 Virtual Private Networking Configuring the Headquarters 133 Virtual Private Networking 134 Virtual Private Networking Remote endpoint settingsLeave the Enable IP Payload Compression checkbox unchecked 135 Virtual Private Networking Connection Tunnel ListRemote party 136 Virtual Private Networking 137 Virtual Private Networking Status 138 Virtual Private Networking 139 Virtual Private Networking 140 Virtual Private Networking NAT Traversal SupportDynamic DNS Support 141 Virtual Private Networking Certificate ManagementExtracting certificates 142 Virtual Private Networking Creating certificates 143 Virtual Private Networking Create the self-signed root CA certificate 144 Virtual Private Networking Adding certificates 145 Virtual Private Networking Adding a CA or CRL certificate 146 Virtual Private Networking Adding a local certificate 147 Virtual Private Networking Troubleshooting 148 Virtual Private Networking 149 Virtual Private Networking 150 Virtual Private Networking CyberGuard SG appliance in Brisbane Internet address Setting up a GRE tunnelLAN address CyberGuard SG appliance in Slough Internet address Remote subnet/netmask 10.1.0.0 GRE over IPSec 154 Virtual Private Networking 155 Virtual Private Networking Local Internal Address Place on Ethernet Bridge 156 Virtual Private Networking Troubleshooting 157 Virtual Private Networking L2TP VPN client 158 Virtual Private Networking L2TP server Date and Time SystemSet date and time NTP time server 160 System Locality 161 System Users Diagnostic AdministrationEncrypted save/restore all User settings Internet access via access controls DiagnosticsPassword Diagnostics 164 System Network tests 165 System Configuration filesSystem log Flash upgrade Reset button Reboot Technical Support 169 Appendix a IP Address Ranges Appendix a IP Address RangesB.c.d B.c.d-e B.c.d-e.f.g.h B.c.d/e 170 Appendix B Terminology Appendix B TerminologyTerm Meaning 171 Appendix B Terminology DNS 172 Appendix B Terminology IDB 173 Appendix B Terminology Isakmp 174 Appendix B Terminology NTP 175 Appendix B Terminology SHA 176 Appendix C System Log Access Logging Eth0 Default DenyEth1 Ppp 179 Appendix C System Log Creating Custom Log Rules 180 Appendix C System Log 181 Appendix C System Log Iptables -I Forward -j LOG -i eth0 -p tcp 182 Appendix C System Log Rate Limiting 183 Appendix C System Log Administrative Access LoggingBoot Log Messages 184 Appendix D Firmware Upgrade Practices and Precaut ions Appendix D Firmware Upgrade Practices and Precautions