NAT from ISDN (Inside) to ethernet (outside)

[tmontestrucq]

I am trying to build a configuration on a cisco 1603 to allow people to reach our network with an isdn connection and with only one ip adress for all these people.
People have ISDN modem and Win98 OS.

I have done a configuration (see below).
1/ With this configuration I can get a connection with my network but NAT
doesn't work and I can't ping my network.
2/ Once the connection is established if I place the dialer in " ip nat
inside" I can ping and everything seems OK.
3/ Unfortunately if I keep this configuration (with dialer1/ip nat inside)
everytime I can not get a connection.

Does anybody have an idea ???
Thank's

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NET#sh run
Building configuration...

Current configuration:
!
version 11.2
no service password-encryption
no service udp-small-servers
no service tcp-small-servers
!
hostname NET
!
enable password cisco
!
username TOTO password 0 TITI
ip subnet-zero
ip nat inside source list 1 interface Ethernet0 overload
no ip domain-lookup
isdn switch-type basic-net3
!
interface Ethernet0
ip address 144.99.87.8 255.0.0.0
no ip directed-broadcast
ip nat outside
no cdp enable
!
interface BRI0
no ip address
no ip directed-broadcast
ip nat inside
encapsulation ppp
bandwidth 64
no keepalive
dialer pool-member 1
no fair-queue
no cdp enable
ppp authentication chap callin
!
interface Dialer1
description Connexion User TOTO
ip unnumbered Ethernet0
ip access-group 101 in
no ip directed-broadcast
encapsulation ppp
dialer remote-name TOTO
dialer idle-timeout 360
dialer pool 1
dialer-group 1
peer default ip address pool NETGROUP1
no fair-queue
no cdp enable
ppp authentication chap callin
!
ip local pool NETGROUP1 192.168.1.1 192.168.1.10
no ip classless
access-list 1 permit any
access-list 101 permit ip 192.168.1.0 0.0.0.255 any
access-list 101 permit icmp any any
no cdp run
dialer-list 1 protocol ip permit
!
line con 0
line vty 0 4
password cisco
login
!
end