===== DMVPN w/ GRE =====
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!
{{:ccnp:dmvpn.png?600|}}
REFER TO THE ABOVE DIAGRAM AND NOTE THE CONFIGS BELOW!
==== CONFIGS ====
=== R1 the HUB ===
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
=== R3 Spoke ===
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/NBMA 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
=== R5 Spoke ===
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
==== Verification and Flow ====
R3#traceroute 5.5.5.5 <-- Loop to Loop
Type escape sequence to abort.
Tracing the route to 5.5.5.5
VRF info: (vrf in name/id, vrf out name/id)
1 10.2.3.2 36 msec 52 msec 48 msec
2 10.1.2.1 52 msec 56 msec 48 msec
3 10.1.4.4 76 msec 72 msec 68 msec
4 10.4.5.5 72 msec 56 msec 76 msec
Tracing the route to 192.168.1.5 <-- Tun to Tun
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
R3#sh ip nhrp
192.168.1.1/32 via 192.168.1.1
Tunnel10 created 00:05:46, never expire
Type: static, Flags: used
NBMA address: 1.1.1.1
192.168.1.5/32 via 192.168.1.5
Tunnel10 created 00:04:05, expire 01:56:06
Type: dynamic, Flags: router used
NBMA address: 5.5.5.5