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Cisco – Two LAN, Two WAN ISP and NAT

We recently received a request from a rural customer who was tired of their unreliable 1Mbps ADSL line to add a second ADSL line to their network. The line was ordered and installed and we then added a second ADSL wic interface to their router and set to work making it work. Our brief was to make it work so that each LAN was associated with one WAN link and only used that WAN link. This is how we went about it.

Clearly the second interface needed to be associated with a second dialer created to log in and manage the second connection. Furthermore, we needed to add a second DHCP pool. This new config is shown as follows:

DHCP config:-

ip dhcp pool pollux
   network 192.168.200.0 255.255.255.0
   default-router 192.168.200.1 
   dns-server 62.6.40.178 62.6.40.162 

As you can see this connection is using BT DNS servers.

Dialer config:-

interface Dialer1
 description btbusiness
 ip address negotiated
 ip mtu 1492
 ip nat outside
 ip virtual-reassembly
 encapsulation ppp
 dialer pool 2
 no cdp enable
 ppp authentication chap pap callin
 ppp chap hostname xxxxxxx
 ppp chap password xxxxxxx

We then needed to allocate a second default route to the router and this was achieved by means of the following command:-
ip route 0.0.0.0 0.0.0.0 Dialer1

We created an access list to handle the new traffic relating to the new DHCP network as follows:-
access-list 22 permit 192.168.200.0 0.0.0.255

and then we added a new access list to ensure that the traffic on each LAN network remained segregated from the other LAN. This was done as follows:-

access-list 112 deny   ip 192.168.1.0 0.0.0.255 10.0.0.0 0.255.255.255
access-list 112 deny   ip 192.168.1.0 0.0.0.255 172.16.0.0 0.15.255.255
access-list 112 deny   ip 192.168.1.0 0.0.0.255 192.168.0.0 0.0.255.255
access-list 112 permit ip 192.168.1.0 0.0.0.255 any
access-list 122 deny   ip 192.168.200.0 0.0.0.255 10.0.0.0 0.255.255.255
access-list 122 deny   ip 192.168.200.0 0.0.0.255 172.16.0.0 0.15.255.255
access-list 122 deny   ip 192.168.200.0 0.0.0.255 192.168.0.0 0.0.255.255
access-list 122 permit ip 192.168.200.0 0.0.0.255 any

Finally we needed to apply route maps to mechanise the access lists, putting them to work maintaining segregation and ensuring correct operation. The following two route maps were configured:-
route-map pollux permit 22
 match ip address 122
 set interface Dialer1
!
route-map castor permit 12
 match ip address 112
 set interface Dialer0

Putting it all together our new configuration was as follows:-

version 12.4
no service pad
service tcp-keepalives-in
service tcp-keepalives-out
service timestamps debug datetime msec
service timestamps log datetime msec
service password-encryption
service sequence-numbers
!
hostname xxx-core-router
!
boot-start-marker
boot-end-marker
!
security authentication failure rate 3 log
security passwords min-length 6
logging buffered 512000 debugging
enable secret xxxxxxx
!
no aaa new-model
no network-clock-participate slot 1 
no network-clock-participate wic 0 
ip cef
!
!
ip auth-proxy max-nodata-conns 3
ip admission max-nodata-conns 3
no ip dhcp use vrf connected
!
ip dhcp pool pollux
   network 192.168.200.0 255.255.255.0
   default-router 192.168.200.1 
   dns-server 62.6.40.178 62.6.40.162 
!
ip dhcp pool castor
   network 192.168.1.0 255.255.255.0
   default-router 192.168.1.1 
   dns-server 62.6.40.178 62.6.40.162 
!
!
ip flow-cache timeout active 1
ip name-server 212.159.13.49
ip name-server 212.159.13.50
ip name-server 141.1.1.1
!
!
!
archive
 log config
  hidekeys
!
!
! 
!
!
!
interface ATM0/0
 description btbusiness
 no ip address
 no ip redirects
 no ip unreachables
 no ip proxy-arp
 no atm ilmi-keepalive
 dsl operating-mode itu-dmt 
 pvc 0/38 
  encapsulation aal5mux ppp dialer
  dialer pool-member 1
 !
!
interface FastEthernet0/0
 ip address 192.168.1.1 255.255.255.0
 ip flow ingress
 ip flow egress
 ip nat inside
 ip virtual-reassembly
 ip route-cache flow
 ip policy route-map castor
 duplex auto
 speed auto
!
interface ATM0/1
 no ip address
 no ip redirects
 no ip unreachables
 no ip proxy-arp
 no atm ilmi-keepalive
 dsl operating-mode itu-dmt 
 pvc 0/38 
  encapsulation aal5mux ppp dialer
  dialer pool-member 2
 !
!
interface FastEthernet0/1
 ip address 192.168.200.1 255.255.255.0
 ip nat inside
 ip virtual-reassembly
 ip policy route-map pollux
 duplex auto
 speed auto
!
interface Dialer0
 ip address negotiated
 ip mtu 1492
 ip nat outside
 ip virtual-reassembly
 encapsulation ppp
 dialer pool 1
 no cdp enable
 ppp authentication chap pap callin
 ppp chap hostname xxxxxxx
 ppp chap password xxxxxxx
!
interface Dialer1
 description btbusiness
 ip address negotiated
 ip mtu 1492
 ip nat outside
 ip virtual-reassembly
 encapsulation ppp
 dialer pool 2
 no cdp enable
 ppp authentication chap pap callin
 ppp chap hostname xxxxxxx
 ppp chap password xxxxxxx
!
router rip
 version 2
 network 192.168.1.0
 network 192.168.200.0
!
ip forward-protocol nd
ip route 0.0.0.0 0.0.0.0 Dialer0
ip route 0.0.0.0 0.0.0.0 Dialer1
ip route 192.168.88.0 255.255.255.0 192.168.200.2
ip route 212.159.13.49 255.255.255.255 Dialer1
ip route 212.159.13.50 255.255.255.255 Dialer1
!
no ip http server
no ip http secure-server
ip nat inside source list 12 interface Dialer0 overload
ip nat inside source list 22 interface Dialer1 overload
ip nat inside source route-map castor interface Dialer1 overload
ip nat inside source route-map pollux interface Dialer0 overload
!
access-list 12 permit 192.168.1.0 0.0.0.255
access-list 22 permit 192.168.200.0 0.0.0.255
access-list 112 deny   ip 192.168.1.0 0.0.0.255 10.0.0.0 0.255.255.255
access-list 112 deny   ip 192.168.1.0 0.0.0.255 172.16.0.0 0.15.255.255
access-list 112 deny   ip 192.168.1.0 0.0.0.255 192.168.0.0 0.0.255.255
access-list 112 permit ip 192.168.1.0 0.0.0.255 any
access-list 122 deny   ip 192.168.200.0 0.0.0.255 10.0.0.0 0.255.255.255
access-list 122 deny   ip 192.168.200.0 0.0.0.255 172.16.0.0 0.15.255.255
access-list 122 deny   ip 192.168.200.0 0.0.0.255 192.168.0.0 0.0.255.255
access-list 122 permit ip 192.168.200.0 0.0.0.255 any
route-map pollux permit 22
 match ip address 122
 set interface Dialer1
!
route-map castor permit 12
 match ip address 112
 set interface Dialer0
!
!
!
control-plane
!
!
!
alias exec arp tclsh flash:arp.tcl
alias exec shutnoshut tclsh flash:shutnoshut.tcl
!
line con 0
line aux 0
line vty 0 4
 access-class 12 in
 password xxxxx
 login
 transport input telnet
!
ntp clock-period 17207966
ntp server 85.119.80.233
!
end

 

The network worked beautifully. Another elegant solution from Rustyice Solutions.

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