ISDN Backup

[dredoggg]

Hey all,
when setting up a isdn backup (for a T1 in this case) we have it so the remote site will dial in to the main office.
So, in the main office I shouldn't have to configure the dialer interface at all.... cause it don't dial just receives.
is this right?

 

[tschouten]

Here are some sample configs from some manual or another with some explenations. This should help you out a little bit. I went with floating static routes as the backup method as I am unsure which you are using.


First Router (This Router calls to Router2)

Current configuration:

version 12.2
!
hostname Router1
!

!--- This username password pair is used for PPP CHAP authentication

username Router2 password 0 letmein
ip subnet-zero
no ip domain-lookup
!
isdn switch-type basic-5ess
!
interface Ethernet0
ip address 172.16.1.1 255.255.255.0
no ip route-cache
no ip mroute-cache
!
interface Serial0

!--- Primary Link.
!--- The bandwidth is adjusted to allow for rapid backup of the link.


!--- This adjusts the EIGRP Hello interval and Hold time for rapid convergence.
!--- The bandwidth command does not actually change the bandwidth of the link,
!--- it only adjusts the routing protocol bandwidth parameter.

bandwidth 2048
ip address 172.16.2.1 255.255.255.128
encapsulation frame-relay
no ip route-cache
no ip mroute-cache
clockrate 64000
!
interface Serial1
no ip address
no ip route-cache
no ip mroute-cache
shutdown
!
interface BRI0

! -- Backup link.

ip address 172.16.3.1 255.255.255.0

! -- The backup link is in a different subnet.
! -- The BRI interface on the peer should also be in this subnet.

encapsulation ppp
no ip route-cache
no ip mroute-cache
dialer map ip 172.16.3.2 name Router2 broadcast 5552000

! -- Dialer map for the peer. Note the IP address and name.
! -- The name must match the authenticated username of the peer.

dialer load-threshold 5 either
dialer-group 1

! -- Apply interesting traffic definition.
! -- Interesting traffic definition is defined in dialer-list 1.

isdn switch-type basic-5ess
ppp authentication chap
ppp multilink
!
router eigrp 100

!--- This example uses eigrp. You can use any routing protocol instead.

network 172.16.0.0
auto-summary
no eigrp log-neighbor-changes
!
ip classless
ip route 172.16.4.0 255.255.255.0 172.16.3.2 200

!--- The floating static route is defined.
!--- Note the administrative distance of the route is 200.
!--- Hence it is only used when all other routes for 172.16.4.0/24
!--- are lost. Note that the next hop for the floating static route
!--- matches the dialer map ip. If the nexthop is not the same as
!--- in the dialer map then the router will no dial.

!
access-list 100 deny eigrp any any
access-list 100 permit ip any any

!--- EIGRP routing packets are denied in the dialer-list.


!--- This prevents eigrp packets from keeping the link up.
!--- Adjust the interesting traffic depending on your traffic definitions.

!
dialer-list 1 protocol ip list 100

!--- Interesting traffic defintion. Use access-list 100.
!--- The interesting traffic is applied to BRI interface using dialer-group 1.

!
line con 0
line aux 0
transport input all
line vty 0 4
login
!
end





Second Router (This Router recieves the call from Router1)


Current configuration:

version 12.2
!
!
hostname Router2
!
username Router1 password 0 letmein
ip subnet-zero
no ip domain-lookup
!
isdn switch-type basic-5ess
!
!
interface Ethernet0
ip address 172.16.4.1 255.255.255.0
!
interface Serial0
bandwidth 2048
ip address 172.16.2.2 255.255.255.128
encapsulation frame-relay
clockrate 64000
!
interface Serial1
no ip address
shutdown
clockrate 64000
!
interface BRI0
ip address 172.16.3.2 255.255.255.0

! -- IP address of backup interface.
! -- This router accepts the call. Note the IP address matches both the
! -- dialer map floating static router nexthop on the peer.

encapsulation ppp
dialer-group 1
isdn switch-type basic-5ess
ppp authentication chap
ppp multilink

!--- The missing dialer map command disables this router from making the call.

!
router eigrp 100
network 172.16.0.0
auto-summary
no eigrp log-neighbor-changes
!
ip classless
ip route 172.16.1.0 255.255.255.0 172.16.3.1 200
!
access-list 100 deny eigrp any any
access-list 100 permit ip any any
dialer-list 1 protocol ip list 100
!
!
line con 0
line aux 0
line vty 0 4
!
end