DYNAMIC MULTI POINT VIRTUAL NETWORK (DMVPN)

What is DMVPN
The DMVPN solution uses Multi point GRE (mGRE) and Next Hop Resolution Protocol (NHRP),A DMVPN is a Secure network that exchange data between sites without needing to pass traffic through an organisation headquarters's private network server or routers

DMVPN relies on two proven technologies:


Next Hop Resolution Protocol (NHRP): Creates a distributed
(NHRP) mapping database of all the spoke tunnels to real
(public interface) addresses
Multipoint GRE Tunnel Interface: Single GRE interface to
support multiple GRE and IPsec tunnels; simplifies size and

complexity of configuration
Next Hop Resolution Protocol (NHRP):
Creates a distributed (NHRP) mapping database of all the spoke tunnels to real (public interface) addresses.
Multipoint GRE Tunnel Interface: Single GRE interface to support multiple GRE and IPsec tunnels; simplifies size and complexity of configuration


DMVPN Components: NHRP

NHRP registration
Spoke dynamically registers its mapping with NHS
Supports spokes with dynamic NBMA addresses or NAT

 NHRP resolutions and redirects
Supports building dynamic spoke-to-spoke tunnels
Control and IP Multicast traffic still through hub
Unicast data traffic direct; reduced load on hub routers


DMVPN Components:Multipoint GRE Tunnels



Single tunnel interface (multipoint)
Non-Broadcast Multi-Access (NBMA) network
Smaller hub configuration
Multicast and broadcast support
Dynamic tunnel destination
Next Hop Resolution Protocol (NHRP)
VPN IP-to-NBMA IP address mapping
Short-cut forwarding
Direct support for dynamic addresses and NAT


NETWORK DESIGN 



(1)Hub-and-spoke
Spoke-to-spoke traffic through hub; requires about the same
number of tunnels as spokes
– Hub bandwidth and CPU limit VPN
– Server Load Balancing: Many “identical” hubs increase
CPU power; spoke-to-spoke design under consideration

(2)Spoke-to-spoke: Dynamic spoke-to-spoke tunnels
Control traffic: Hub-and-spoke; hub to hub
– Hub-and-spoke single-layer
– Hierarchical hub-and-spoke layers
Unicast data traffic: Dynamic mesh
– Spoke routers support spoke-to-hub and spoke-to-spoke tunnels
Number of tunnels falls between the number of spokes n and n2
where n is the number of spokes (full-mesh)



LAB SESSION :

OBJECTIVE : SPOKE 1 and SPOKE 2 Will directly communicate with each other. NHRP protocol will dynamically discovered the route

TOPOLOGY 


R1 CONFIGURATION 
interface FastEthernet0/0
 ip address 10.1.1.1 255.255.255.0
 no shutdown
 interface Serial1/0
 ip address 50.10.1.2 255.255.255.252
 no ip split-horizon
 no shutdown

 interface Tunnel0
 ip address 192.168.1.1 255.255.255.248
 no ip redirects
 ip nhrp authentication aosl
 ip nhrp map multicast dynamic
 ip nhrp network-id 1
 no ip split-horizon
 tunnel source Serial1/0
 tunnel mode gre multipoint
 tunnel key 1234

router rip
 version 2
 network 10.0.0.0
 network 192.168.1.0
 no auto-summary

ip route 0.0.0.0 0.0.0.0 50.10.1.1

R2: ISP CONFIGURATION
interface Serial1/0
 ip address 50.10.1.1 255.255.255.252
  no shutdown
interface Serial1/1
 ip address 50.10.1.9 255.255.255.252
 no shutdown
interface Serial1/2
 ip address 50.10.1.5 255.255.255.252
 no shutdown
R3 CONFIGURATION 

nterface FastEthernet0/0
 ip address 10.1.3.1 255.255.255.0
 no shutdown
interface Serial1/0
 ip address 50.10.1.10 255.255.255.252
 no shutdown
interface Tunnel0
 ip address 192.168.1.3 255.255.255.248
 no ip redirects
 ip nhrp authentication aosl
 ip nhrp map multicast dynamic
 ip nhrp map 192.168.1.1 50.10.1.2
 ip nhrp map multicast 50.10.1.2
 ip nhrp network-id 1
 ip nhrp nhs 192.168.1.1
 no ip split-horizon
 tunnel source Serial1/0
 tunnel mode gre multipoint
 tunnel key 1234

router rip
 version 2
 network 10.0.0.0
 network 192.168.1.0
 no auto-summary


ip route 0.0.0.0 0.0.0.0 50.10.1.9


R4 CONFIGURATION 

interface FastEthernet0/0
 ip address 10.1.2.1 255.255.255.0
 no shutdown
interface Serial1/0
 ip address 50.10.1.6 255.255.255.252
 no shutdown
interface Tunnel0
 ip address 192.168.1.2 255.255.255.248
 no ip redirects
 ip nhrp authentication aosl
 ip nhrp map multicast dynamic
 ip nhrp map 192.168.1.1 50.10.1.2
 ip nhrp map multicast 50.10.1.2
 ip nhrp network-id 1
 ip nhrp nhs 192.168.1.1
 no ip split-horizon
 tunnel source Serial1/0
 tunnel mode gre multipoint
 tunnel key 1234

router rip
 version 2
 network 10.0.0.0
 network 192.168.1.0

 no auto-summary

ip route 0.0.0.0 0.0.0.0 50.10.1.5

Out put To Veryfy the DMPVN :

Go to R3 Console and 

R3#ping 10.1.2.1

192.168.1.2/32 via 192.168.1.2, Tunnel0 created 22:36:56, expire 01:50:45
  Type: dynamic, Flags: router nat 
  NBMA address: 50.10.1.6 
192.168.1.3/32 via 192.168.1.3, Tunnel0 created 22:36:55, expire 01:58:03
  Type: dynamic, Flags: unique nat registered 
  NBMA address: 50.10.1.10 



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