Dynamic GRE

Based upon mGRE information.

Hub (3745)

interface Loopback0
 description SprintTunnel
 ip address  <hub-loopback-ip  255.255.255.255

interface Tunnel8
 ip address  <tunnel-interface-ip>  255.255.255.252
 no ip redirects
 ip nhrp authentication cisco
 ip nhrp map multicast dynamic
 ip nhrp network-id 123
 tunnel source Loopback0
 tunnel mode gre multipoint
 tunnel key 123

Spoke (871W)

interface Dialer0
 description WAN_PPP
 ip dhcp client update dns server none
 ip ddns update hostname host.domain.com
 ip ddns update sdm_ddns1
 ip address negotiated
 ip mtu 1452
 ip nat outside
 ip inspect sip in
 ip virtual-reassembly
 encapsulation ppp
 carrier-delay msec 0
 dialer pool 1
 dialer-group 1
 keepalive 1
 ppp authentication chap pap callin
 ppp chap hostname username@qwest.net
 ppp chap password 7 1335407E73
 ppp pap sent-username username@qwest.net password 7 01263C5B79
 crypto map l2tpmap

interface Tunnel8
 ip address  <tunnel-interface-ip>  255.255.255.252
 no ip redirects
 ip nhrp authentication cisco
 ip nhrp map <hub-tunnel-interface-ip> <hub-loopback-ip> 
 ip nhrp map multicast <hub-tunnel-interface-ip> 
 ip nhrp network-id 123
 ip nhrp nhs <hub-tunnel-interface-ip> 
 tunnel source Dialer0
 tunnel mode gre multipoint
 tunnel key 123
 tunnel path-mtu-discovery