I've been working across many sites around the world with ADSL. The first output below is the one I've used many many times & I'm therefore most familiar with. It's from a site in the UK.
interface ATM0 no ip address no atm ilmi-keepalive pvc 0/38 encapsulation aal5mux ppp dialer dialer pool-member 1 ! interface Dialer1 ip address negotiated encapsulation ppp dialer pool 1 dialer-group 1 ppp chap hostname xxxxxx ppp chap password xxxxxx ppp authentication chap callin
I understand how this works. Now the stuff I don't understand. This config below has been taken from a site in Turin in Italy.
interface ATM0/1/0 no ip address ip mtu 1492 atm bandwidth dynamic no atm ilmi-keepalive ! interface ATM0/1/0.1 point-to-point ip address xxxxx xxxxxx ip mtu 1492 pvc 8/35 vbr-nrt 896 896 1 encapsulation aal5snap max-reserved-bandwidth 97
This is the only stuff in the config to get it working. There is no dialer, no ppp username or password. This is literally all the config (except obviously a default route) required to get it working. So please may someone explain to me how this works?
The way I've been taught is that you get your sync (basically a physically good network to the ISP, i.e. layer 1 connectivity). Next you get a session, which is where you create your PPP session to the ISP, who authenticates you (this is layer2). Finally, at layer 3 you can then get to the internet (i.e. beyond the ISP's network). So how does this aal5snap work, and how does this config work to get them to the internet?