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Internet-based WAN Backup Solutions using NetVanta The Internet as an Alternative
61200890L1-29.4A Copyright © 2005 ADTRAN, Inc. 9
Solution 3 - Primary = ISP via PPPoE/DSL-Cable, Alternate = ISP via Dial-up
In this scenario (see Figure 3), the remote site has two ISP accounts, one via PPPoE using a DSL or cable
modem and another via dial-up. Both are protected by the NetVanta firewall. This PPPoE connection is
always on and is used for local Internet access (if the corporate security policy allows such connectivity) as
well as being used as the primary path to the central site. The central site has a protected Internet
connection and an IPSec VPN gateway for Internet-based access to the central site network. The remote
site uses IPSec VPN to connect to the central VPN gateway over its PPPoE interface as a primary. Should
the PPPoE link fail, a dial-up connection is invoked to a local ISP. Another IPSec VPN connection is
negotiated across the Internet to the central site VPN gateway, re-establishing connectivity between the
two sites.
If the remote router accesses the central VPN gateway on the same IP address no matter which remote
router interface is active, it is important that both devices support IKE dead peer detection. Otherwise,
when the remote site switches to the other interface, the IPSec and/or IKE SA (depending on the exact
configuration) have to age out naturally before a new VPN connection is established. Dead peer detection
expedites this process, allowing the alternate VPN connection to be established more quickly.
Note that this configuration is shown using the NetVanta DIM Carrier Module (1200877L1), which allows
the dial backup interface module (DIM) to be used without a network interface module (NIM) installed.
Figure 3. Primary WAN Connectivity via IPsec VPN over PPPoE/DSL-Cable ISP Connection, Backup
Connectivity via IPsec VPN Dialup ISP Connection
Remote NetVanta Router Configuration:
!
hostname "NV_Remote"
!
ip routing
!
ip firewall
!
!
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