!debug nhrp all
interface r4-gre0
 ip nhrp holdtime 10
 ip nhrp network-id 42
 ip nhrp registration no-unique
 ip nhrp nhs dynamic nbma 192.168.1.1 
 ip nhrp nhs dynamic nbma 192.168.1.2
 ip nhrp nhs dynamic nbma 192.168.1.3
 ip nhrp shortcut
 tunnel source r4-eth0
exit