Hello,
here is a sample configuration for 4 links on the same router configured for load balancing. At the bottom of this post, you can find a couple remarks regarding this configuration:
R1 Configuration
ip cef
!
interface FastEthernet0/1
ip address 192.168.1.1 255.255.255.0
ip nat inside
!
interface ATM0
no ip address
no ip route-cache
no atm ilmi-keepalive
dsl operating-mode auto
!
interface ATM0.1 point-to-point
no ip route-cache
pvc 0/38
encapsulation aal5mux ppp dialer
dialer pool-member 1
!
interface ATM0.2 point-to-point
no ip route-cache
pvc 0/38
encapsulation aal5mux ppp dialer
dialer pool-member 2
!
interface ATM0.3 point-to-point
no ip route-cache
pvc 0/38
encapsulation aal5mux ppp dialer
dialer pool-member 3
!
interface ATM0.4 point-to-point
no ip route-cache
pvc 0/38
encapsulation aal5mux ppp dialer
dialer pool-member 4
!
interface Dialer1
description ISP1_Connection_1
ip address dhcp
ip mtu 1452
encapsulation ppp
dialer pool 1
dialer-group 1
ppp authentication chap pap callin
ppp chap hostname USERNAME
ppp chap password 0 PASSWORD
ppp pap sent-username USERNAME password PASSWORD
!
interface Dialer2
description ISP1_Connection_2
ip address dhcp
ip mtu 1452
encapsulation ppp
dialer pool 2
dialer-group 1
ppp authentication chap pap callin
ppp chap hostname USERNAME
ppp chap password 0 PASSWORD
ppp pap sent-username USERNAME password PASSWORD
!
interface Dialer3
description ISP1_Connection_3
ip address dhcp
ip mtu 1452
encapsulation ppp
dialer pool 3
dialer-group 1
ppp authentication chap pap callin
ppp chap hostname USERNAME
ppp chap password 0 PASSWORD
ppp pap sent-username USERNAME password PASSWORD
interface Dialer4
description ISP1_Connection_4
ip address dhcp
ip mtu 1452
encapsulation ppp
dialer pool 4
dialer-group 1
ppp authentication chap pap callin
ppp chap hostname USERNAME
ppp chap password 0 PASSWORD
ppp pap sent-username USERNAME password PASSWORD
!
ip nat inside source route-map ISP1_Connection_1 interface Dialer1 overload
ip nat inside source route-map ISP1_Connection_2 interface Dialer2 overload
ip nat inside source route-map ISP1_Connection_3 interface Dialer3 overload
ip nat inside source route-map ISP1_Connection_4 interface Dialer4 overload
!
access-list 1 permit 192.168.1.0
!
route-map ISP1_Connection_1 permit 10
match ip address 1
match interface Dialer1
!
route-map ISP1_Connection_2 permit 10
match ip address 1
match interface Dialer2
!
route-map ISP1_Connection_3 permit 10
match ip address 1
match interface Dialer3
!
route-map ISP1_Connection_4 permit 10
match ip address 1
match interface Dialer4
!
ip route 0.0.0.0 0.0.0.0 Dialer1
ip route 0.0.0.0 0.0.0.0 Dialer2
ip route 0.0.0.0 0.0.0.0 Dialer3
ip route 0.0.0.0 0.0.0.0 Dialer4
!
dialer-list 1 protocol ip permit
The following applies:
- the use of four static routes will allow load-balancing over the four links and provide redundancy at the same time
- the NAT configuration will dynamically choose the NAT'ed address depending on which interface CEF has been chosen to send the packet out of
- enabling CEF with four default routes will by default load balance per-destination, which means for every source and destination address pair, CEF creates a hash and chooses one of the routes in the routing table.
- enabling CEF on a router will load balance outgoing traffic only, not incoming traffic. If your ISP uses Cisco, you could ask for the ISP to enable CEF on their end as well, which would result in inbound load balancing.
To verify load balancing, use the EXEC command:
sh ip cef 0.0.0.0
HTH,
GNT
