ADTRAN NetVanta Internet-Based WAN Backup Manuale utente

61200890L1-29.4A

May 2005

Configuration Guide

Internet-based WAN Backup Solutions

using NetVanta

Overview

This configuration guide delineates the advantages of using the NetVanta

product line and the Internet for wide area network (WAN) connectivity. It

includes example scenarios using Internet-based backup solutions.

Introduction Internet-based WAN Backup Solutions using NetVanta

Introduction

WAN communication links are traditionally the weakest component in computer networking. Unlike LAN

components, which are typically in the owner's direct physical and administrative control, the facilities that

make up the WAN link belong to and are controlled by a third party. These facilities also cover wide

geographic areas, making them more susceptible to physical harm. Such characteristics make WAN links

the single largest contributor to network downtime.

When the WAN link is critical to a network's operation, it is wise to design towards WAN resiliency. In

some cases, the volume and criticality of the WAN might dictate the need to completely duplicate the

WAN with redundant and independent facilities. The cost of this solution can be quite high, so the benefit

must be carefully weighed.

Another common solution, especially in large hub and spoke networks, is to use dial backup around the

WAN provider. In this solution, should a spoke lose its WAN connectivity to the hub, it will place a call to

a dial-up server located at the hub, completely bypassing the WAN. While this is a well known solution

that has been used for many years, the cost of dial-up server ownership, maintenance, and long distance

toll charges can be quite high.

The Internet as an Alternative

Using the stateful inspection firewall and powerful IPSec VPN capabilities provided in the NetVanta router

product line, the Internet can be a useful and low cost alternative for WAN connectivity -- as a backup or

even as a primary connection. Internet use eliminates the dial-up server and its ownership and maintenance

expenses, in effect outsourcing management of the modem bank to local ISPs at each location. It also

eliminates toll charges since each location can connect via a local ISP. A site can remain connected

indefinitely for a flat fee in many areas, incurring no toll charges.

Following are descriptions and detailed examples of several Internet-based backup solutions. These

solutions have been tested with AOS Version 8.0.22E.

Note that detailed firewall design and VPN design are dependent on each network's unique requirements.

The examples shown here are simpified to focus on the mechanics of using a primary and backup

connection.

Also note that in these examples, the NetVanta is the remote site router. A NetVanta or a third party device

can be used as the central router and the central FW/VPN gateway.

Internet-based WAN Backup Solutions using NetVanta The Internet as an Alternative

Solution 1 - Primary = Frame Relay Service Provider, Alternate = ISP via Dial-up

In this scenario (see Figure 1), a Frame Relay service provider supplies the Frame Relay access line and

virtual circuit that connects a NetVanta remote site directly to the central site. Since this link is entirely

over a provider's Frame Relay network, no firewall or VPN is required to protect the customer's network.

The central site also has a protected Internet connection and an IPSec VPN gateway for Internet-based

access to the central site network. The remote site has a dial-up resource (analog modem or ISDN) and an

account at a local ISP. Should the remote's Frame Relay link fail, a dial-up connection is invoked to a local

ISP. An IPSec VPN connection is established across the Internet to the central site VPN gateway,

re-establishing connectivity between the two sites. The NetVanta uses its stateful inspection firewall to

protect the remote network while connected to the ISP. When the Frame Relay connection is

re-established, the dial backup connection is dropped and the IPSec connection ages out. The dial

connection to the Internet is used solely as a backup link, and general Internet access is not provided.

Figure 1. Primary WAN Connectivity via Frame Relay Service Provider, Backup Connectivity via

IPsec VPN over Dial-up Internet Connection

Remote NetVanta Router Configuration:

hostname "NV_Remote"

ip routing

ip firewall

ip crypto

crypto ike policy 100

initiate aggressive

no respond

10.254.255.25/28

10.254.255.85/28

10.254.255.26/28

10.1.1.240/24

172.31.4.0/24

The Internet as an Alternative Internet-based WAN Backup Solutions using NetVanta

local-id fqdn REMOTE

peer 10.254.255.85

attribute 10

authentication pre-share

group 2

lifetime 300

crypto ike remote-id fqdn CENTRAL. preshared-key 1234567890

crypto ipsec transform-set dessha esp-des esp-sha-hmac

mode tunnel

crypto map HOSTviaDIAL 100 ipsec-ike

match address REMOTE_to_CENTRAL

set peer 10.254.255.85

set transform-set dessha

set security-association lifetime seconds 600

set pfs group2

interface eth 0/1

ip address

access-policy LOCALLAN

no shutdown

interface t1 1/1

clock source internal

tdm-group 1 timeslots 1-24 speed 64

no shutdown

interface bri 1/3

description ISDN link to local PSTN

isdn spid1 11111

isdn spid2 11112

no shutdown

interface fr 1 point-to-point

description Interface to FR Service Provider - PRIMARY

frame-relay lmi-type ansi

no shutdown

cross-connect 1 t1 1/1 1 frame-relay 1

interface fr 1.1 point-to-point

description VC to CENTRAL

frame-relay interface-dlci 100

Internet-based WAN Backup Solutions using NetVanta The Internet as an Alternative

ip address 10.254.255.26 255.255.255.252

access-policy FR

dial-backup number 2222 digital-64k 1 1 ppp 2

! link interface ppp 2/ISDN for dial backup in case this VC is lost

interface ppp 2

description Dial Backup Interface to ISP with Firewall, VPN to CENTRAL Gateway

ip address negotiated

access-policy DIAL

crypto map HOSTviaDIAL

ppp authentication chap

username ISP_Dial_Srv password a

ppp chap hostname ISP_Customer_Dial

ppp chap password a

no shutdown

ip access-list extended REMOTE_to_CENTRAL

remark permits local lan subnet to central subnet

permit ip 10.1.1.240 0.0.0.15 172.31.4.0 0.0.0.255

! each interface has its own policy class to allow for

! discrete destination policy control if needed

ip policy-class DIAL ! inbound on dial only allows sessions from CENTRAL

allow reverse list REMOTE_to_CENTRAL

ip policy-class FR ! inbound on FR allows any session from CENTRAL

allow reverse list REMOTE_to_CENTRAL

ip policy-class LOCALLAN ! outbound on LAN allows any session to CENTRAL

allow list REMOTE_to_CENTRAL

ip route 0.0.0.0 0.0.0.0 fr 1.1 ! static to primary.

ip route 0.0.0.0 0.0.0.0 ppp 2 3 ! floating static to the dial backup link should the

! fr iface go down.

end

The Internet as an Alternative Internet-based WAN Backup Solutions using NetVanta

Solution 2 - Primary = Frame Relay Service Provider, Alternate = ISP via

PPPoE/DSL-Cable

In this scenario (see Figure 2), a Frame Relay service provider supplies the Frame Relay access line and

virtual circuit that connects a NetVanta remote site directly to the central site. Since this link is entirely

over a provider's Frame Relay network, no firewall or VPN is required to protect the customer's network.

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 also has a PPPoE over DSL or cable modem to a local ISP. This

connection is always on and is used for local Internet access (if the corporate security policy allows such

connectivity) while providing an alternate path to the central site. This link is protected by the NetVanta

firewall. Should the NetVanta's Frame Relay link fail, an IPSec VPN connection is established over the

PPPoE connection across the Internet to the central site's VPN gateway, re-establishing connectivity

between the two sites. The NetVanta uses its stateful inspection firewall to protect the PPPoE connection to

the Internet.

Figure 2. Primary WAN Connectivity via Frame Relay Service Provider, Backup Connectivity via

IPsec VPN over PPPoE/DSL-Cable ISP Connection

Remote NetVanta Router Configuration:

hostname "NV_Remote"

ip routing

ip firewall

ip crypto

crypto ike policy 100

initiate aggressive

no respond

10.254.255.25/28

10.254.255.85/28

10.254.255.26/28

10.1.1.240/24

172.31.4.0/24

Internet-based WAN Backup Solutions using NetVanta The Internet as an Alternative

local-id fqdn REMOTE

peer 10.254.255.85

attribute 10

authentication pre-share

group 2

lifetime 300

crypto ike remote-id fqdn CENTRAL. preshared-key 1234567890

crypto ipsec transform-set dessha esp-des esp-sha-hmac

mode tunnel

crypto map HOSTviaPoE 100 ipsec-ike

match address REMOTE_to_CENTRAL

set peer 10.254.255.85

set transform-set dessha

set security-association lifetime seconds 600

set pfs group2

interface eth 0/1

description Local Lan Interface

ip address 10.1.1.254 255.255.255.240

access-policy LOCALLAN

no shutdown

interface eth 0/2

description Ethernet to DSL/Cable Modem

no ip address

no shutdown

interface t1 1/1

clock source internal

tdm-group 1 timeslots 1-24 speed 64

no shutdown

interface fr 1 point-to-point

description Interface to FR Service Provider - PRIMARY

frame-relay lmi-type ansi

no shutdown

cross-connect 1 t1 1/1 1 frame-relay 1

interface fr 1.1 point-to-point

description VC to Central

frame-relay interface-dlci 100

ip address 10.254.255.26 255.255.255.252

The Internet as an Alternative Internet-based WAN Backup Solutions using NetVanta

access-policy FR

interface ppp 1

description PPPoE Interface to ISP with Firewall, VPN to CENTRAL Gateway

ip address negotiated

access-policy PoE

crypto map HOSTviaPoE

ppp authentication chap

username ISP_PPPoE_Srv password a

ppp chap hostname ISP_Customer_PPPoE

ppp chap password a

mtu 1492

no shutdown

cross-connect 2 eth 0/2 ppp 1

ip access-list extended Internet

permit ip 10.1.1.240 0.0.0.15 any

ip access-list extended REMOTE_to_CENTRAL

remark permits local lan subnet to central sub

permit ip 10.1.1.240 0.0.0.15 172.31.4.0 0.0.0.255

! each interface has its own policy class to allow for

! discrete destination policy control if needed

ip policy-class FR ! inbound on FR allows any session from CENTRAL

allow reverse list REMOTE_to_CENTRAL

ip policy-class LOCALLAN ! outbound on LAN allows any session to CENTRAL

! and outbound Internet access (with nat)

allow list REMOTE_to_CENTRAL

nat source list Internet interface ppp 1 overload policy PoE! Internet sessions are limited to egress

! interfaces with the PoE policy class

ip policy-class PoE ! inbound on PoE allows any session from CENTRAL

allow reverse list REMOTE_to_CENTRAL

Ip route 0.0.0.0 0.0.0.0 ppp 1 ! Internet traffic

ip route 172.31.4.0 255.255.255.0 fr 1.1 ! traffic to central over primary

ip route 172.31.4.0 255.255.255.0 ppp 1 3 ! traffic to central over backup

end

Internet-based WAN Backup Solutions using NetVanta The Internet as an Alternative

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

10.254.255.85/28

10.254.255.26/28

10.1.1.240/24

172.31.4.0/24

The Internet as an Alternative Internet-based WAN Backup Solutions using NetVanta

ip firewall fast-nat-failover

! If using the PPPoE and Dial-up ISP connections for local Internet access

! and using 'NAT source' with the address of the currently active interface, the

! previous command is necessary to allow sessions started on one interface to be

! terminated when the route to the destination switches to the other interface.

ip crypto

crypto ike policy 100

initiate aggressive

no respond

local-id fqdn REMOTE

peer 10.254.255.85

attribute 10

authentication pre-share

group 2

lifetime 300

crypto ike remote-id fqdn CENTRAL. preshared-key 1234567890

crypto ipsec transform-set dessha esp-des esp-sha-hmac

mode tunnel

! separate crypto maps are used to allow for future customization of

! individual VPN connections if needed

crypto map HOSTviaDIAL 100 ipsec-ike

match address REMOTE_to_CENTRAL

set peer 10.254.255.85

set transform-set dessha

set security-association lifetime seconds 600

set pfs group2

crypto map HOSTviaPoE 100 ipsec-ike

match address REMOTE_to_CENTRAL

set peer 10.254.255.85

set transform-set dessha

set security-association lifetime seconds 600

set pfs group2

interface eth 0/1

description Local Lan Interface

ip address 10.1.1.254 255.255.255.240

access-policy LOCALLAN

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