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JunosE 11.2.x IP Services Configuration Guide
GRE Flows Through NAT
Monitoring NAT
Displaying the NAT License Key
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Figure 11: PPTP Tunnels on an Outside Network
The router has installed an inside source static simple translation in its translation table
as follows:
Inside Local Address
11.11.11.1
The PPTP client initiates its tunnels to the inside global address 20.0.0.1. The E Series
router translates packets destined for address 20.0.0.1 and forwards them to the inside
local address of 11.11.11.1. Because GRE traffic can pass through NAT, all matching PPTP
control packets are translated and forwarded to the destination.
Because PPTP requires the use of GRE flows, the examples in the previous section also
work for any GRE traffic flows that traverse NAT.
GRE flows can terminate at an E Series router if NAT is or is not enabled. When the router
receives locally terminating inbound GRE packets, the router transmits the packets to
the tunnel server module for GRE processing. If the packets require translating, they are
again sent through the tunnel server module.
NOTE: Only inner IP headers are translated for terminating GRE flows; outer IP headers
are never translated.
For outbound GRE packets, the process works in reverse. If the packets require translation,
the router transmits the packets to the tunnel server module for translation. If the packets
are destined for a GRE tunnel, they are again sent through the tunnel server module where
an outer header is prepended to the packet and the packet is then sent to the appropriate
GRE tunnel.
This section explains how to view NAT license information, NAT statistics, NAT translation
entries, NAT address pool information, and NAT inside and outside rule settings.
The show license nat command displays the NAT license key.
Inside Global Address
20.0.0.1
Copyright © 2010, Juniper Networks, Inc.
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