ATM PVC configuration requires you to enter a map for the remote end. A map statement must be entered before you can even ping your own atm interface.

Router#conf ter
Enter configuration commands, one per line.  End with CNTL/Z.
Router(config)#hostname R1
R1(config)#line con 0
R1(config-line)#logg syn
R1(config-line)#exec-time 0 0
R1(config-line)#exit
R1(config)#no ip domain loo
R1(config)#int a1/0
R1(config-if)#ip add 10.1.12.1 255.255.255.0
R1(config-if)#pvc 1/102
R1(config-if-atm-vc)#protocol 10.1.12.2 br
 

Do not forget the broadcast parameter
for routing protocols and/or multicast traffic, To be able to ping your own interface.

R1(config-if-atm-vc)#protocol 10.1.12.1
R1(config-if-atm-vc)#encap ?
aal5mux    AAL5+MUX Encapsulation
aal5nlpid  AAL5+NLPID Encapsulation
aal5snap   AAL5+LLC/SNAP Encapsulation
 

AAL5Mux can only run one protocol while AAL5Snap can run multiple protocols.

R1(config-if-atm-vc)#encap aal5mux    ?
fr-atm-srv   Frame Relay/ATM service interworking
frame-relay  Frame Relay/ATM network interworking
ip           IP
voice        Voice over ATM
 

R1(config-if-atm-vc)#encap aal5nlpid ?

R1(config-if-atm-vc)#encap aal5snap
R1(config-if-atm-vc)#
 

Cisco Documentation:

aal5mux: AAL and encapsulation type for multiplex (MUX)-type VCs. A protocol must be specified when using this encapsulation type.

•appletalk—AppleTalk protocol.

•decnet—DECnet protocol.

•frame-relay—Frame Relay-ATM Network Interworking (FRF.5) on the Cisco MC3810.

•fr-atm-srv—Frame Relay-ATM Service Interworking (FRF.8) on the Cisco MC3810.

•ip—IP protocol.

•ipx—IPX protocol.

•ppp virtual-template number—Internet Engineering Task Force (IETF)-compliant PPP over ATM. Use the virtual-template number options to identify the virtual template. Supported on ATM PVCs only.

•voice—Voice over ATM.

aal5nlpid: AAL and encapsulation type that allows ATM interfaces to interoperate with High-Speed Serial Interfaces (HSSIs) that are using an ATM data service unit (ADSU) and running ATM-Data Exchange Interface (DXI). Supported on ATM PVCs only.

aal5snap: AAL and encapsulation type that supports Inverse ARP. Logical Link Control/Subnetwork Access Protocol (LLC/SNAP) precedes the protocol datagra

Final Configuration:

R1(config-if)#do show run int a1/0
Building configuration...

Current configuration : 181 bytes
!
interface ATM1/0
 ip address 10.1.12.1 255.255.255.0
 no atm ilmi-keepalive
 pvc 1/102
 protocol ip 10.1.12.1
 protocol ip 10.1.12.2 broadcast
 encapsulation aal5snap
 !
end
 

@R2 this is the configuration:

Router#conf ter
Enter configuration commands, one per line.  End with CNTL/Z.
Router(config)#hostname R2
R2(config)#line con 0
R2(config-line)#logg syn
R2(config-line)#exec-time 0 0
R2(config-line)#exit
R2(config)#no ip domain loo
R2(config)#int lo0
R2(config-if)#ip add 150.2.2.
*Oct 13 12:28:02.639: %LINEPROTO-5-UPDOWN: Line protocol on Interface Loopback0,
 changed state to up
R2(config-if)#ip add 150.2.2.2 255.255.255.255
R2(config-if)#exit
R2(config)#int a1/0
R2(config-if)#ip add 10.1.12.2 255.255.255.0
R2(config-if)#pvc 1/201
R2(config-if-atm-vc)#protoco 10.1.12.1 b
R2(config-if-atm-vc)#protoco 10.1.12.2
R2(config-if-atm-vc)#encap aal5snap
R2(config-if-atm-vc)#exit
R2(config-if)#no sh
R2(config-if)#do show run int a1/0
Building configuration...

Current configuration : 181 bytes
!
interface ATM1/0
 ip address 10.1.12.2 255.255.255.0
 no atm ilmi-keepalive
 pvc 1/201
 protocol ip 10.1.12.1 broadcast
 protocol ip 10.1.12.2
 encapsulation aal5snap
 !
end

R1#ping 10.1.12.1

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.1.12.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 16/86/168 ms</pre>

Ping to the remote device

R1#ping 10.1.12.2

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.1.12.2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 8/72/164 ms
R1#