Cisco Cisco Expressway
n
Dual interfaces are selected and the external LAN interface is set to LAN2
n
Configuration > IPv4 gateway is set to 10.0.10.1, the local IP address of the NAT router
n
LAN1 > IPv4 address is set to 10.0.20.2
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LAN1 > IPv4 static NAT mode is set to Off
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LAN2 > IPv4 address is set to 10.0.10.2
n
LAN2 > IPv4 static NAT mode is set to On
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LAN2 > IPv4 static NAT address is set to 64.100.0.10, the public NAT address of the NAT router
When enabling IPv4 static NAT mode on an interface (LAN2 in our example), the Expressway-E will modify
the payload of H.323 and SIP messages sent out via this interface, so that references to the LAN2 interface
address (10.0.10.2) are replaced with the IPv4 static NAT address configured for this interface (64.100.0.10).
This means that when looking at the payload of SIP and H.323 messages sent out via this interface, it will
appear as if the LAN2 interface has an IP address of 64.100.0.10.
the payload of H.323 and SIP messages sent out via this interface, so that references to the LAN2 interface
address (10.0.10.2) are replaced with the IPv4 static NAT address configured for this interface (64.100.0.10).
This means that when looking at the payload of SIP and H.323 messages sent out via this interface, it will
appear as if the LAN2 interface has an IP address of 64.100.0.10.
It is important to note that the Expressway-E will not modify the layer 3 source address of outgoing H.323
and SIP packets sent out of this interface, as this will be done by the NAT router.
and SIP packets sent out of this interface, as this will be done by the NAT router.
With this configuration in place, the SIP INVITE shown in Figure 4 will now look as follows as it arrives at
endpoint B:
endpoint B:
Packet header:
Source IP: 64.100.0.10
Destination IP: 64.100.0.20
SIP payload:
INVITE sip: 64.100.0.20 SIP/2.0
Cisco Expressway Basic Configuration Deployment Guide (X8.5)
Page 48 of 56
Appendix 4: Advanced network deployments