D-Link DFL-2560 Product Manual - Page 271

Solution A - Using NAT, Destination Port, Service, TCP/UDP, Record-Route, source, Allow

Page 271 highlights

6.2.8. The SIP ALG Chapter 6. Security Mechanisms This scenario can be implemented in two ways: • Using NAT to hide the network topology. • Without NAT so the network topology is exposed. Solution A - Using NAT Here, the proxy and the local clients are hidden behind the IP address of the NetDefend Firewall. The setup steps are as follows: 1. Define a single SIP ALG object using the options described above. 2. Define a Service object which is associated with the SIP ALG object. The service should have: • Destination Port set to 5060 (the default SIP signalling port) • Type set to TCP/UDP 3. Define three rules in the IP rule set: • A NAT rule for outbound traffic from the local proxy and the clients on the internal network to the remote clients on, for example, the Internet. The SIP ALG will take care of all address translation needed by the NAT rule. This translation will occur both on the IP level and the application level. Neither the clients or the proxies need to be aware that the local clients are being NATed. If Record-Route is enabled on the SIP proxy, the source network of the NAT rule can include only the SIP proxy, and not the local clients. • A SAT rule for redirecting inbound SIP traffic to the private IP address of the NATed local proxy. This rule will have core as the destination interface (in other words NetDefendOS itself) since inbound traffic will be sent to the private IP address of the SIP proxy. • An Allow rule which matches the same type of traffic as the SAT rule defined in the previous step. OutboundFrom ProxyUsers InboundTo ProxyAndClients InboundTo ProxyAndClients Action NAT SAT SETDEST ip_proxy Allow Src Interface lan wan Src Network lannet (ip_proxy) all-nets Dest Interface Dest Network wan all-nets core wan_ip wan all-nets core wan_ip 271

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This scenario can be implemented in two ways:
Using NAT to hide the network topology.
Without NAT so the network topology is exposed.
Solution A - Using NAT
Here, the proxy and the local clients are hidden behind the IP address of the NetDefend Firewall.
The setup steps are as follows:
1.
Define a single SIP ALG object using the options described above.
2.
Define a
Service
object which is associated with the SIP ALG object. The service should have:
Destination Port
set to
5060
(the default SIP signalling port)
Type
set to
TCP/UDP
3.
Define three rules in the IP rule set:
A
NAT
rule for outbound traffic from the local proxy and the clients on the internal network
to the remote clients on, for example, the Internet. The SIP ALG will take care of all
address translation needed by the
NAT
rule. This translation will occur both on the IP level
and the application level. Neither the clients or the proxies need to be aware that the local
clients are being NATed.
If
Record-Route
is enabled on the SIP proxy, the
source
network of the
NAT
rule can
include only the SIP proxy, and not the local clients.
A
SAT
rule for redirecting inbound SIP traffic to the private IP address of the NATed local
proxy. This rule will have
core
as the destination interface (in other words NetDefendOS
itself) since inbound traffic will be sent to the private IP address of the SIP proxy.
An
Allow
rule which matches the same type of traffic as the
SAT
rule defined in the
previous step.
Action
Src Interface
Src Network
Dest Interface
Dest Network
OutboundFrom
ProxyUsers
NAT
lan
lannet
(ip_proxy)
wan
all-nets
InboundTo
ProxyAndClients
SAT
SETDEST
ip_proxy
wan
all-nets
core
wan_ip
InboundTo
ProxyAndClients
Allow
wan
all-nets
core
wan_ip
6.2.8. The SIP ALG
Chapter 6. Security Mechanisms
271