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Redundant DMVPN network

Today I looked at the configuration DMVPN (Dynamic Multipoint VPN). A Dynamic Multipoint Virtual Private Network is an enhancement of the virtual private network (VPN) configuration process of Cisco IOS-based routers. DMVPN prevents the need for pre-configured (static) IPsec peers in crypto-map configurations and ISAKMP peer statements. This feature of Cisco IOS allows greater scalability over previous IPsec configurations. An IPsec tunnel between two Cisco routers may be created on an as needed basis.

I have created a situation with GNS3, where I have two hub routers and one spoke router. This situation creates extra redundancy when connecting to the hub location. There are two ways to configure redundancy in DMVPN:

  1. Dual hub-dual DMVPN cloud
  2. Dual hub-single DMVPN cloud

In the first scenario the hub routers are connecting to there own DMVPN network. This means that the spoke need to configure two tunnel interfaces to connect to two different DMVPN networks. In the second scenario both hub routers connect to the same DMVPN network. I configured the second scenario using GNS3. The figure below shows my practice setup.

redundant_dmvpn

The configuration from the three routers can be found below.

router R0

key chain authen-hsrp
key 1
key-string hsrp@test
key chain authen-eigrp
key 1
key-string eigrp@test
!
crypto isakmp policy 10
encr aes 256
authentication pre-share
group 5
crypto isakmp key pr3sh@r3d-k3y address 0.0.0.0 0.0.0.0
crypto isakmp invalid-spi-recovery
crypto isakmp keepalive 120 30 periodic
!
!
crypto ipsec transform-set stong-ts esp-aes 256 esp-sha-hmac
!
crypto ipsec profile dmvpn
set transform-set strong-ts
set pfs group5
!
interface Tunnel0
ip address 192.168.255.1 255.255.255.0
no ip redirects
ip mtu 1440
ip hello-interval eigp 1024 15
ip hold-time eigrp 1024 45
no ip next-hop-self eigrp 1024
ip authentication mode eigrp 1024 md5
ip authentication key-chain eigrp 1024 authen-eigrp
ip nhrp authentication nhrp@booches
ip nhrp map multicast dynamic
ip nhrp network-id 1
ip nhrp holdtime 600
no ip split-horizon eigrp 1024
tunnel source FastEthernet0/0
tunnel mode gre multipoint
tunnel key 1
tunnel protection ipsec profile dmvpn
!
interface FastEthernet0/0
description outside
ip address 80.80.10.2 255.255.255.0
duplex auto
speed auto
!
interface FastEthernet0/1
description inside
ip address 10.10.13.2 255.255.255.0
duplex auto
speed auto
standby 1 ip 10.10.13.1
standby 1 priority 200
standby 1 preempt
standby 1 authentication md5 key-chain authen-hsrp
!
router eigrp 1024
network 10.10.13.2 0.0.0.0
network 192.168.255.1 0.0.0.0
no auto-summary

router R1

key chain authen-hsrp
key 1
key-string hsrp@test
key chain authen-eigrp
key 1
key-string eigrp@test
!
crypto isakmp policy 10
encr aes 256
authentication pre-share
group 5
crypto isakmp key pr3sh@r3d-k3y address 0.0.0.0 0.0.0.0
crypto isakmp invalid-spi-recovery
crypto isakmp keepalive 120 30 periodic
!
crypto ipsec transform-set strong-ts esp-aes 256 esp-sha-hmac
!
crypto ipsec profile dmvpn
set transform-set strong-ts
set pfs group5
!
interface Tunnel0
ip address 192.168.255.2 255.255.255.0
no ip redirects
ip mtu 1440
ip hello-interval eigrp 1024 15
ip hold-time eigrp 1024 45
no ip next-hop-self eigrp 1024
ip authentication mode eigrp 1024 md5
ip authentication key-chain eigrp 1024 authen-eigrp
ip nhrp authentication nhrp@booces
ip nhrp map multicast dynamic
ip nhrp network-id 1
ip nhrp holdtime 600
no ip split-horizon eigrp 1024
tunnel source FastEthernet0/0
tunnel mode gre multipoint
tunnel key 1
tunnel protection ipsec profile dmvpn
!
interface FastEthernet0/0
description outside
ip address 50.50.1.3 255.255.255.0
duplex auto
speed auto
!
interface FastEthernet0/1
description inside
ip address 10.10.13.3 255.255.255.0
duplex auto
speed auto
standby 1 ip 10.10.13.1
standby 1 priority 100
standby 1 preempt
standby 1 authentication md5 key-chain authen-hsrp
!
router eigrp 1024
network 10.10.13.3 0.0.0.0
network 192.168.255.2 0.0.0.0
no auto-summary

router R3

key chain authen-eigrp
key 1
key-string eigrp@booches
!
crypto isakmp policy 10
encr aes 256
authentication pre-share
group 5
crypto isakmp key pr3sh@r3d-k3y address 0.0.0.0 0.0.0.0
crypto isakmp invalid-spi-recovery
crypto isakmp keepalive 120 30 periodic
!
crypto ipsec transform-set strong-ts esp-aes 256 esp-sha-hmac
!
crypto ipsec profile dmvpn
set transform-set strong-ts
set pfs group
!
interface Tunnel0
ip address 192.168.255.3 255.255.255.0
no ip redirects
ip mtu 1440
ip hello-interval eigrp 1024 15
ip hold-time eigrp 1024 45
ip authentication mode eigrp 1024 md5
ip authentication key-chain eigrp 1024 authen-eigrp
ip nhrp authentication nhrp@booches
ip nhrp map multicast dynamic
ip nhrp map 192.168.255.1 80.80.10.2
ip nhrp map multicast 80.80.10.2
ip nhrp map 192.168.255.2 50.50.1.3
ip nhrp map multicast 50.50.1.3
ip nhrp network-id 1
ip nhrp holdtime 600
ip nhrp nhs 192.168.255.1
ip nhrp nhs 192.168.255.2
no ip route-cache cef
no ip route-cache
no ip mroute-cache
tunnel source FastEthernet0/0
tunnel mode gre multipoint
tunnel key 1
tunnel protection ipsec profile dmvpn shared
!
interface FastEthernet0/0
description outside
ip address 40.40.10.4 255.255.255.0
speed auto
duplex auto
!
interface FastEthernet0/1
description inside
ip address 192.168.1.1 255.255.255.0
speed auto
duplex auto
!
router eigrp 1024
network 192.168.1.1 0.0.0.0
network 192.168.255.3 0.0.0.0
no auto-summary

I configured EIGRP authentication as an extra feature. This setup was configured with GNS3, so I guess it needs more tweaking to implement it in a real network. It should however provide a solid base for configuring a redundant DMVPN solution.

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René Jorissen

Co-owner and Solution Specialist at 4IP Solutions
René Jorissen works as Solution Specialist for 4IP in the Netherlands. Network Infrastructures are the primary focus. René works with equipment of multiple vendors, like Cisco, Aruba Networks, FortiNet, HP Networking, Juniper Networks, RSA SecurID, AeroHive, Microsoft and many more. René is Aruba Certified Edge Expert (ACEX #26), Aruba Certified Mobility Expert (ACMX #438), Aruba Certified ClearPass Expert (ACCX #725), Aruba Certified Design Expert (ACDX #760), CCNP R&S, FCNSP and Certified Ethical Hacker (CEF) certified. You can follow René on Twitter and LinkedIn.

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