Cisco Cisco Expressway
This deployment consists of:
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DMZ subnet 1 – 10.0.10.0/24, containing:
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the internal interface of Firewall A – 10.0.10.1
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the LAN2 interface of the Expressway-E – 10.0.10.2
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DMZ subnet 2 – 10.0.20.0/24, containing:
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the external interface of Firewall B – 10.0.20.1
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the LAN1 interface of the Expressway-E – 10.0.20.2
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LAN subnet – 10.0.30.0/24, containing:
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the internal interface of Firewall B – 10.0.30.1
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the LAN1 interface of the Expressway-C – 10.0.30.2
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Firewall A is the ouward-facing firewall; it is configured with a NAT IP (public IP) of 64.100.0.10 which is statically
NATed to 10.0.10.2 (the LAN2 interface address of the Expressway-E)
NATed to 10.0.10.2 (the LAN2 interface address of the Expressway-E)
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Firewall B is the internally-facing firewall
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Expressway-E LAN1 has static NAT mode disabled
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Expressway-E LAN2 has static NAT mode enabled with Static NAT address 64.100.0.10
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Expressway-C has a traversal client zone pointing to 10.0.20.2 (LAN1 of the Expressway-E)
With the above deployment, there is no regular routing between the 10.0.20.0/24 and 10.0.10.0/24 subnets. The
Expressway-E bridges these subnets and acts as a proxy for SIP/H.323 signaling and RTP /RTCP media.
Expressway-E bridges these subnets and acts as a proxy for SIP/H.323 signaling and RTP /RTCP media.
Static Routes Towards the Internal Network
, you would typically configure the
private address of the external firewall (10.0.10.1 in the diagram) as the default gateway of the Expressway-E. Traffic that
has no more specific route is sent out from either Expressway-E interface to 10.0.10.1.
has no more specific route is sent out from either Expressway-E interface to 10.0.10.1.
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If the internal firewall (B) is doing NAT for traffic from the internal network (subnet 10.0.30.0 in diagram) to LAN1
of the Expressway-E (for example traversal client traffic from Expressway-C), that traffic is recognized as being
from the same subnet (10.0.20.0 in diagram) as it reaches LAN1 of the Expressway-E. The Expressway-E will
therefore be able to reply to this traffic through its LAN1 interface.
of the Expressway-E (for example traversal client traffic from Expressway-C), that traffic is recognized as being
from the same subnet (10.0.20.0 in diagram) as it reaches LAN1 of the Expressway-E. The Expressway-E will
therefore be able to reply to this traffic through its LAN1 interface.
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If the internal firewall (B) is not doing NAT for traffic from the internal network (subnet 10.0.30.0 in diagram) to
LAN1 of the Expressway-E (for example traversal client traffic from Expressway-C), that traffic still has the
originating IP address (for example, 10.0.30.2 for traffic from Expressway-C in the diagram). You must create a
static route towards that source from LAN1 on the Expressway-E, or the return traffic will go to the default gateway
(10.0.10.1). You can do this on the web UI (System > Network interfaces > Static routes) or using
LAN1 of the Expressway-E (for example traversal client traffic from Expressway-C), that traffic still has the
originating IP address (for example, 10.0.30.2 for traffic from Expressway-C in the diagram). You must create a
static route towards that source from LAN1 on the Expressway-E, or the return traffic will go to the default gateway
(10.0.10.1). You can do this on the web UI (System > Network interfaces > Static routes) or using
xCommand
RouteAdd
at the CLI.
If the Expressway-E needs to communicate with other devices behind the internal firewall (eg. for reaching
network services such as NTP, DNS, LDAP/AD and syslog servers), you also need to add static routes from
Expressway-E LAN1 to those devices/subnets.
network services such as NTP, DNS, LDAP/AD and syslog servers), you also need to add static routes from
Expressway-E LAN1 to those devices/subnets.
In this particular example, we want to tell the Expressway-E that it can reach the 10.0.30.0/24 subnet behind the
10.0.20.1 firewall (router), which is reachable via the LAN1 interface. This is accomplished using the following
10.0.20.1 firewall (router), which is reachable via the LAN1 interface. This is accomplished using the following
xCommand
RouteAdd
syntax:
xCommand RouteAdd Address: 10.0.30.0 PrefixLength: 24 Gateway: 10.0.20.1 Interface: LAN1
In this example, the
Interface
parameter could also be set to
Auto
as the gateway address (10.0.20.1) is only reachable
via LAN1.
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Cisco Expressway-E and Expressway-C - Basic Configuration Deployment Guide