Cisco 2600 ADSL with failover to Ethernet with NAT

Good afternoon everyone,

I am having trouble setting up a simple failover configuration.

We have 2 connections (one is Fiber @ 10Mbit, other is ADSL @ 6Mbit).

The Fiber usage is expensive, so for client usage I was looking at
using our ADSL as a base, but failover to the Fiber if the DSL
disconnects / goes down. My servers are running on other routers, so
this router is strictly for client NAT.

The problem:
If I start this configuration up fresh it works. The system will NAT
through the ADSL connection and all is well. I then do a “shutdown” on
Dialer1. It continues to work fine and automatically switches to the
Fiber connection. I then do a “no shutdown” on Dialer1 and the whole
thing stops working. The ADSL connection gets an IP, but something
seems to be messed up with the NAT part. I can’t even traceroute from
the router. Everything times out.


My current setup:
eth0/0: fiber connection {static IP}
eth0/1: LAN
Dialer1: PPPOE ADSL {dynamic IP}

My running config:
version 12.3

memory-size iomem 15
clock timezone EST -5
aaa new-model
aaa session-id common
ip subnet-zero
no ip source-route
no ip cef
no ip ftp passive
no ip bootp server
ip audit po max-events 100
ip ssh time-out 60
ip ssh authentication-retries 2

interface ATM0/0
no ip address
no atm ilmi-keepalive
bundle-enable
dsl operating-mode auto

interface ATM0/0.1 point-to-point
pvc 0/35
pppoe-client dial-pool-number 1

interface Ethernet0/0
bandwidth 5000
ip address [OurExternalFiberIP] 255.255.255.248
no ip proxy-arp
ip nat outside
no ip route-cache
half-duplex
no cdp enable

interface Ethernet0/1
ip address 192.168.0.1 255.255.255.0
no ip proxy-arp
ip nat inside
no ip route-cache
half-duplex
no cdp enable

interface Dialer1
bandwidth 7000
ip address negotiated
ip mtu 1492
ip nat outside
encapsulation ppp
no ip route-cache
ip tcp adjust-mss 1452
dialer pool 1
no cdp enable
ppp chap hostname [Login]
ppp chap password 0 [Password]
ppp pap sent-username [Login] password 0 [Password]

ip nat inside source route-map Fiber interface Ethernet0/0 overload
ip nat inside source route-map ADSL interface Dialer1 overload

no ip http server
no ip http secure-server

ip classless

ip route 0.0.0.0 0.0.0.0 Dialer1 10
ip route 0.0.0.0 0.0.0.0 [OurFiberGatewayAddress] 20

ip route 192.168.0.0 255.255.255.0 Ethernet0/1
ip route [OurFiberStaticNetworkAddress] 255.255.255.248 Ethernet0/0

access-list 1 permit 0.0.0.0
access-list 1 permit 192.168.0.0 0.0.0.255

no cdp run

route-map Fiber permit 10
match ip address 1
match interface Ethernet0/0
!
route-map ADSL permit 10
match ip address 1
match interface Dialer1

Thanks,
Jack
jbaker (at) neustyle [dot] com
.

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