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Primary backup mode ISP internet links (ILL, PPPOE) configuration using IP SLA monitor

I am posting an article for circuit redundancy used in working scenario.

Router is Cisco 1841 with IOS image c1841-spservicesk9-mz.124-15.T12.bin.

Router has three Fast Ethernet interfaces, each one for ISP1, ISP2 and customer LAN.

Router is connected with two Internet circuits.

Primary as internet lease line (ILL) with static IP and Tunnel config and NATed with IP POOL connected to ISP1.

Backup as PPPOE broadband with dynamic IP address connected to ISP2.

Tokai Rubber_Bangalore1.jpg

Router#sh run
Building configuration...

Current configuration : 2653 bytes
version 12.4
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
hostname Router
enable password XXXXXXX
no aaa new-model
dot11 syslog
ip cef
no ip dhcp use vrf connected
ip dhcp excluded-address
ip dhcp excluded-address 192.168.1.X
ip dhcp pool Customer_LAN
   dns-server 218.248.x.x 203.124.16.x.x
   lease 2
ip name-server 203.124.x.x
ip name-server 218.248.x.x
multilink bundle-name authenticated
vpdn enable
vpdn-group 1
  protocol pppoe
l2tp tunnel receive-window 1024
log config
track 1 rtr 1 reachability
bba-group pppoe global
interface Tunnel1
description ISP1 - Tunnel
ip address 10.x.x.4
ip nat outside
ip virtual-reassembly
tunnel source 71.x.x.2
tunnel destination 71.x.x.10
interface FastEthernet0/0

description ISP1 - Internet lease line
ip address 71.x.x.2
duplex auto
speed auto
interface FastEthernet0/1
description ISP2 DSL interface for Internet
no ip address
ip virtual-reassembly
duplex auto
speed auto
pppoe enable group global
pppoe-client dial-pool-number 1
interface FastEthernet0/0/0

description Customer LAN
ip address 110.x.x.205 secondary
ip address
ip nat inside
ip virtual-reassembly
duplex auto
speed auto
interface Dialer1
ip address negotiated
ip mtu 1492
ip nat outside
ip virtual-reassembly
encapsulation ppp
dialer pool 1
dialer-group 1
no cdp enable
ppp authentication chap callin
ppp chap hostname xxxxxxx (username given by ISP)
ppp chap password 0 xxxxxxxxx (Password given by ISP)

ip forward-protocol nd
ip route Tunnel1 track 1
ip route 71.x.x.1 track 1
ip route Dialer1 200
ip http server
no ip http secure-server
ip nat pool ISP1-Pool 110.x.x.205 110.x.x.205 netmask
ip nat inside source route-map ISP1-NAT pool ISP1-Pool overload

ip nat inside source route-map ISP2-NAT interface Dialer1 overload
ip sla 1
icmp-echo 71.x.x.1 source-interface FastEthernet0/0
timeout 1000
threshold 40
frequency 3
ip sla schedule 1 life forever start-time now

access-list 1 permit

no cdp run

route-map ISP1-NAT permit 10
match ip address 1
set interface FastEthernet0/0
route-map ISP2-NAT permit 10
match ip address 1
match interface Dialer1
line con 0
line aux 0
line vty 0 4
password XXXXXX
scheduler allocate 20000 1000

Router#sh ver
Cisco IOS Software, 1841 Software (C1841-SPSERVICESK9-M), Version 12.4(15)T12, RELEASE SOFTWARE (fc3)
Technical Support:
Copyright (c) 1986-2010 by Cisco Systems, Inc.
Compiled Fri 22-Jan-10 00:40 by prod_rel_team

ROM: System Bootstrap, Version 12.4(13r)T, RELEASE SOFTWARE (fc1)

Router uptime is 17 hours, 21 minutes
System returned to ROM by reload at 11:24:31 UTC Mon Oct 11 2010
System image file is "flash:c1841-spservicesk9-mz.124-15.T12.bin"

This product contains cryptographic features and is subject to United
States and local country laws governing import, export, transfer and
use. Delivery of Cisco cryptographic products does not imply
third-party authority to import, export, distribute or use encryption.
Importers, exporters, distributors and users are responsible for
compliance with U.S. and local country laws. By using this product you
agree to comply with applicable laws and regulations. If you are unable
to comply with U.S. and local laws, return this product immediately.

A summary of U.S. laws governing Cisco cryptographic products may be found at:

If you require further assistance please contact us by sending email to

Cisco 1841 (revision 7.0) with 235520K/26624K bytes of memory.
Processor board ID FHKXXXXXXXX
3 FastEthernet interfaces
DRAM configuration is 64 bits wide with parity disabled.
191K bytes of NVRAM.
62720K bytes of ATA CompactFlash (Read/Write)

Configuration register is 0x2102


Version history
Revision #:
1 of 1
Last update:
‎10-11-2010 10:16 PM
Updated by:
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