Telindus 1031, User And Reference Manual

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Telindus 1031 Router Chapter 7
User manual Configuring the router
122
7.4.5 PAT limitations
Example of PAT and multiple remote networks over Frame Relay
Suppose your network is connected to the Internet via a Frame Relay network and to another site that
does not have official IP addresses either.
Now you have to choose whether to apply PAT to:
• all traffic towards the Frame Relay network
or
• the traffic destined for the Internet only.
Suppose PAT is only used for the traffic destined for the Internet. In that case, the configuration of the
most relevant attributes of the Telindus 1031 Router is as follows:
• telindus1031/router/defaultRoute = { gateway = 195.7.12.254; interface = wan }
• telindus1031/router/routingTable = { network = 192.168.48.0; gateway = 195.7.12.23 }
• telindus1031/router/defaultNat/patAddress = 195.7.12.22
As you can see, the gateway attribute is not configured since the Internet traffic uses the default route.
Limitations
As seen from the previous, Port Address Translation has some limitations:
• Only outgoing sessions are supported. This implies that you can not access servers on your local net-
work over the Internet.
• Some TCP or UDP applications do not support port translation.
• Limited ICMP support.
Router
(+ modem)
modem
your site
ISP
Internet
IP subnet 192.168.47.0
mask 255.255.255.0
IP address WAN interface
= 195.7.12.254
Frame Relay or
PDH/SDH network
IP address WAN interface
= 195.7.12.22
IP address LAN interface
= 192.168.47.254
other site
IP subnet 192.168.48.0
mask 255.255.255.0
IP address WAN interface
= 195.7.12.23