Abrer_Wiki

GRE tunnels, but dynamic, yanno?

Going to skip the explanation until I hit this part in the books, but until then - a refresher on quick Phase 2 configuration from a Hub/spoke topology with one HUB. And excuse the terrible diagram, I'll build a better one one I'm not pressed for time!

REFER TO THE ABOVE DIAGRAM AND NOTE THE CONFIGS BELOW!

interface Tunnel10
 ip address 192.168.1.1 255.255.255.0  <-- Tun Addr
 no ip redirects
 ip nhrp network-id 1         <-- Activates NHRP
 tunnel source Loopback0
 tunnel mode gre multipoint   <-- Enable DMVPN
end

interface Tunnel10
 ip address 192.168.1.3 255.255.255.0    <-- Set IP for Tun INT
 no ip redirects
 ip nhrp map 192.168.1.1 1.1.1.1         <-- Map Phys address for NHS aka How do I get to 192.168.1.1?
 ip nhrp network-id 3                    <-- Useful for multi-hub environments. Details later...
 ip nhrp nhs 192.168.1.1                 <-- Specify NHS for tunnel traffic to traverse.
 tunnel source Loopback0                
 tunnel mode gre multipoint              <-- Enable Dynamic Multipoint VPN
end

interface Tunnel10
 ip address 192.168.1.5 255.255.255.0
 no ip redirects
 ip nhrp map 192.168.1.1 1.1.1.1
 ip nhrp network-id 5
 ip nhrp nhs 192.168.1.1
 tunnel source Loopback0
 tunnel mode gre multipoint
end

Tracing the route to 192.168.1.5
VRF info: (vrf in name/id, vrf out name/id)
  1 192.168.1.5 88 msec 76 msec 76 msec
R3#sh dmvpn | b Type     
Type:Spoke, NHRP Peers:2, 

 # Ent  Peer NBMA Addr Peer Tunnel Add State  UpDn Tm Attrb
 ----- --------------- --------------- ----- -------- -----
     1 1.1.1.1             192.168.1.1    UP 00:01:24     S
     1 5.5.5.5             192.168.1.5    UP 00:01:23     D