CCIE Study Notes

Cisco IOS DMVPN Overview is a good place to start for conceptual information about DMVPN. For configuration information, you should look at DMVPN Configuration Guide, IOS 15M&T.

This is the one with hub and spoke and NHRP with mGRE interfaces. Don't forget vrf-aware DMVPN and MP-BGP.

Example hub configuration:

crypto isakmp policy 1
encr aes
authentication pre-share
group 14
crypto isakmp key cisco47 address 0.0.0.0
!
crypto ipsec transform-set trans2 esp-aes esp-sha-hmac
mode transport
!
crypto ipsec profile vpnprof
set transform-set trans2
!
interface Tunnel0
bandwidth 1000
ip address 10.0.0.1 255.255.255.0
! Ensures longer packets are fragmented before they are encrypted; otherwise, the receiving router would have to do the reassembly.
ip mtu 1400
! The following line must match on all nodes that “want to use” this mGRE tunnel:
ip nhrp authentication donttell
! Note that the next line is required only on the hub.
ip nhrp map multicast dynamic
! The following line must match on all nodes that want to use this mGRE tunnel:
ip nhrp network-id 99
ip nhrp holdtime 300
! Turns off split horizon on the mGRE tunnel interface; otherwise, EIGRP will not advertise routes that are learned via the mGRE interface back out that interface.
no ip split-horizon eigrp 1
! Enables dynamic, direct spoke-to-spoke tunnels when using EIGRP.
no ip next-hop-self eigrp 1
ip tcp adjust-mss 1360
delay 1000
! Sets IPsec peer address to Ethernet interface’s public address.
tunnel source Ethernet0
tunnel mode gre multipoint
! The following line must match on all nodes that want to use this mGRE tunnel.
tunnel key 100000
tunnel protection ipsec profile vpnprof
!
interface Ethernet0
ip address 172.17.0.1 255.255.255.0
!
interface Ethernet1
ip address 192.168.0.1 255.255.255.0
!
router eigrp 1
network 10.0.0.0 0.0.0.255
network 192.168.0.0 0.0.0.255
!

Example spoke configuration:

crypto isakmp policy 1
encr aes
authentication pre-share
group 14
crypto isakmp key cisco47 address 0.0.0.0
!
crypto ipsec transform-set trans2 esp-aes esp-sha-hmac
mode transport
!
crypto ipsec profile vpnprof
set transform-set trans2
!
interface Tunnel0
bandwidth 1000
ip address 10.0.0.2 255.255.255.0
ip mtu 1400
! The following line must match on all nodes that want to use this mGRE tunnel:
ip nhrp authentication donttell
! Definition of NHRP server at the hub (10.0.0.1), which is permanently mapped to the static public address of the hub (172.17.0.1).
ip nhrp map 10.0.0.1 172.17.0.1
! Sends multicast packets to the hub router, and enables the use of a dynamic routing protocol between the spoke and the hub.
ip nhrp map multicast 172.17.0.1
! The following line must match on all nodes that want to use this mGRE tunnel:
ip nhrp network-id 99
ip nhrp holdtime 300
! Configures the hub router as the NHRP next-hop server.
ip nhrp nhs 10.0.0.1
ip tcp adjust-mss 1360
delay 1000
tunnel source Ethernet0
tunnel mode gre multipoint
! The following line must match on all nodes that want to use this mGRE tunnel:
tunnel key 100000
tunnel protection ipsec profile vpnprof
!
! This is a spoke, so the public address might be dynamically assigned via DHCP.
interface Ethernet0
ip address dhcp hostname Spoke1
!
interface Ethernet1
ip address 192.168.1.1 255.255.255.0
!
! EIGRP is configured to run over the inside physical interface and the tunnel.
router eigrp 1
network 10.0.0.0 0.0.0.255
network 192.168.1.0 0.0.0.255