DMVPN Phase 1:
R1配置:
R1_HUB#show run int tunnel 0
Building configuration...
Current configuration : 219 bytes
!
interface Tunnel0
ip address 172.168.123.1 255.255.255.0
no ip redirects
ip nhrp map multicast dynamic
ip nhrp network-id 1
tunnel source Ethernet0/0
tunnel mode gre multipoint
end
R2 / R3 配置:
R2_spoke#show run int tunnel 0
Building configuration...
Current configuration : 241 bytes
!
interface Tunnel0
ip address 172.168.123.2 255.255.255.0
ip nhrp map 172.168.123.1 10.1.14.1
ip nhrp map multicast 10.1.14.1
ip nhrp network-id 1
ip nhrp nhs 172.168.123.1
tunnel source Ethernet0/0
tunnel destination 10.1.14.1
end
至此R1 和 R2， R1和R3 之间的tunnel就建立起来， DMVPN phase 1 Spoke 之间不会有直连的tunnel.
R1_HUB#show dmvpn
Legend: Attrb --> S - Static, D - Dynamic, I - Incomplete
N - NATed, L - Local, X - No Socket
T1 - Route Installed, T2 - Nexthop-override
C - CTS Capable
# Ent --> Number of NHRP entries with same NBMA peer
NHS Status: E --> Expecting Replies, R --> Responding, W --> Waiting
UpDn Time --> Up or Down Time for a Tunnel
==========================================================================
Interface: Tunnel0, IPv4 NHRP Details
Type:Hub, NHRP Peers:2,
# Ent Peer NBMA Addr Peer Tunnel Add State UpDn Tm Attrb
----- --------------- --------------- ----- -------- -----
1 10.1.24.2 172.168.123.2 UP 1w3d D
1 10.1.34.3 172.168.123.3 UP 1w3d D
R1_HUB#show ip nhr
R1_HUB#show ip nhrp
172.168.123.2/32 via 172.168.123.2
Tunnel0 created 1w3d, expire 01:37:11
Type: dynamic, Flags: unique registered used nhop
NBMA address: 10.1.24.2
172.168.123.3/32 via 172.168.123.3
Tunnel0 created 1w3d, expire 01:55:34
Type: dynamic, Flags: unique registered used nhop
NBMA address: 10.1.34.3
Spoke之间需要互相访问， 需要经过HUB, 所以在起路由协议后， 需要在HUB侧关闭水平分割，发布summary路由以减少spoke router的路由数量.
DMVPN Phase 1 一定要保证Hub端作为Spoke访问其他Spoke路由的下一跳，如果使用EIGRP需要在Hub端关闭水平分割；如果使用OSPF需要在Hub使用点到多点的网络接口类型；如果使用BGP建议使用eBGP。
R1_HUB(config)#int tu0
R1_HUB(config-if)#no ip split-horizon eigrp 1
R1_HUB(config-if)#ip summary-address eigrp 1 192.168.0.0 255.255.255.0
R1_HUB#show ip route eigrp 1
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP
a - application route
+ - replicated route, % - next hop override
Gateway of last resort is not set
D 192.168.0.0/16 is a summary, 00:01:04, Null0
D 192.168.2.0/24 [90/27008000] via 172.168.123.2, 1w3d, Tunnel0
D 192.168.3.0/24 [90/27008000] via 172.168.123.3, 1w3d, Tunnel0
R2_spoke#show ip route eigrp 1
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP
a - application route
+ - replicated route, % - next hop override
Gateway of last resort is not set
D 192.168.0.0/16 [90/27008000] via 172.168.123.1, 00:01:09, Tunnel0
R2_spoke#
R2_spoke#traceroute 192.168.3.3 source 192.168.2.2
Type escape sequence to abort.
Tracing the route to 192.168.3.3
VRF info: (vrf in name/id, vrf out name/id)
1 172.168.123.1 5 msec 5 msec 0 msec
2 172.168.123.3 1 msec 1 msec *
DMVPN Phase 2:
Hub和Spoke都配置mGRE，这样Spoke可以自动建立到其他Spoke的隧道。
R2_spoke(config)#in tunnel 0
R2_spoke(config-if)#no tunnel destination 10.1.14.1
R2_spoke(config-if)#tunnel mode gre multipoint
如果使用EIGRP需要在Hub端不仅需要关闭水平分割，还要关闭下一跳自我(Disable next-hop-self)；如果使用OSPF，需要使用broadcast的接口网络类型，同时要保证Hub端为DR，所有的Spoke端要配置端口priority为0；使用BGP的话，用iBGP或eBGP中的next-hop-unchanged。
R1_HUB(config)#int tunnel 0
R1_HUB(config-if)#no ip summary-address eigrp 1 192.168.0.0 255.255.0.0
R1_HUB(config-if)#no ip next-hop-self eigrp 1
运行DMVPN的阶段二以后，会发现阶段二的问题在于Hub端不能汇总，因为汇总后的路由下一跳在Hub上，那这样Spoke去往Spoke的话，首先会发包给Hub端，就又有了次优路径好增大了延迟。
R2_spoke# show ip route eigrp 1
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP
a - application route
+ - replicated route, % - next hop override
Gateway of last resort is not set
D 192.168.1.0/24 [90/27008000] via 172.168.123.1, 00:01:29, Tunnel0
D 192.168.3.0/24 [90/28288000] via 172.168.123.3, 00:01:29, Tunnel0
R2_spoke#ping 192.168.3.3 source 192.168.2.2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.3.3, timeout is 2 seconds:
Packet sent with a source address of 192.168.2.2
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/13/65 ms
R2_spoke#
R2_spoke#
R2_spoke#show dmvpn
Legend: Attrb --> S - Static, D - Dynamic, I - Incomplete
N - NATed, L - Local, X - No Socket
T1 - Route Installed, T2 - Nexthop-override
C - CTS Capable
# Ent --> Number of NHRP entries with same NBMA peer
NHS Status: E --> Expecting Replies, R --> Responding, W --> Waiting
UpDn Time --> Up or Down Time for a Tunnel
==========================================================================
Interface: Tunnel0, IPv4 NHRP Details
Type:Spoke, NHRP Peers:2,
# Ent Peer NBMA Addr Peer Tunnel Add State UpDn Tm Attrb
----- --------------- --------------- ----- -------- -----
1 10.1.14.1 172.168.123.1 UP 00:01:52 S
1 10.1.34.3 172.168.123.3 UP 00:00:06 D
R2_spoke#
R2_spoke#trac
R2_spoke#traceroute 192.168.3.3 source 192.168.2.2
Type escape sequence to abort.
Tracing the route to 192.168.3.3
VRF info: (vrf in name/id, vrf out name/id)
1 172.168.123.3 0 msec 1 msec *
R2_spoke#
DMVPN Phase 3:
在阶段三中同样有阶段二的功能，也就是支持Spoke到Spoke直接的隧道，但是并不是用路由协议来解决Spoke学到其他Spoke路由下一跳的问题，而是使用NHRP的重定向来解决。
当Spoke1要访问Spoke2的路由时，假如下一跳在Hub上，第一个包会发往Hub，Hub会转发这个数据包给Spoke2，同时会发送一个NHRP的重定向消息给Spoke1，Spoke1收到后，会储存重定向消息并向Spoke2发送NHRP query消息，Spoke2收到NHRP query会存储Spoke1的信息，Spoke1和Spoke2之间会自动建立隧道，后续的数据包会直接从Spoke1发往Spoke2,不经过Hub。
这样的优化的好处是Spoke学习到其他Spoke的路由下一跳不需要在Spoke上了，这样Hub就可以只发送汇总路由和默认路由给Spoke端，可以解决阶段二的可伸缩性问题。
在阶段三中运行路由协议时，不需要保留下一跳信息，EIGRP关闭水平分割就可以；OSPF运行P2MP的接口网络类型就可以，不需要broadcast了.
R1_HUB(config)#int tunnel 0
R1_HUB(config-if)#ip next-hop-self eigrp 1
R1_HUB(config-if)#ip summary-address eigrp 1 192.168.0.0 255.255.0.0
R1_HUB(config-if)#ip nhrp redirect
R1_HUB#show run int tunnel 0
Building configuration...
Current configuration : 289 bytes
!
interface Tunnel0
ip address 172.168.123.1 255.255.255.0
no ip redirects
no ip split-horizon eigrp 1
ip nhrp map multicast dynamic
ip nhrp network-id 1
ip nhrp redirect
ip summary-address eigrp 1 192.168.0.0 255.255.0.0
tunnel source Ethernet0/0
tunnel mode gre multipoint
R2_spoke(config)#int tunnel 0
R2_spoke(config-if)#ip nhrp shortcut
R2_spoke#show run int tunnel 0
Building configuration...
Current configuration : 274 bytes
!
interface Tunnel0
ip address 172.168.123.2 255.255.255.0
no ip redirects
ip nhrp map 172.168.123.1 10.1.14.1
ip nhrp map multicast 10.1.14.1
ip nhrp network-id 1
ip nhrp nhs 172.168.123.1
ip nhrp shortcut
tunnel source Ethernet0/0
tunnel mode gre multipoint
end
R2_spoke#show ip route eigrp 1
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP
a - application route
+ - replicated route, % - next hop override
Gateway of last resort is not set
D 192.168.0.0/16 [90/27008000] via 172.168.123.1, 00:00:12, Tunnel0
R2_spoke#tr
R2_spoke#traceroute 192.168.3.3 so
R2_spoke#traceroute 192.168.3.3 source 192.168.2.2
Type escape sequence to abort.
Tracing the route to 192.168.3.3
VRF info: (vrf in name/id, vrf out name/id)
1 172.168.123.1 5 msec 5 msec 0 msec
2 172.168.123.3 5 msec 6 msec *
R2_spoke#show ip nhrp
172.168.123.1/32 via 172.168.123.1
Tunnel0 created 00:01:08, never expire
Type: static, Flags: used
NBMA address: 10.1.14.1
172.168.123.3/32 via 172.168.123.3
Tunnel0 created 00:00:18, expire 01:59:41
Type: dynamic, Flags: router used nhop rib
NBMA address: 10.1.34.3
192.168.3.0/24 via 172.168.123.3
Tunnel0 created 00:00:18, expire 01:59:41
Type: dynamic, Flags: router rib
NBMA address: 10.1.34.3
R2_spoke#traceroute 192.168.3.3 source 192.168.2.2
Type escape sequence to abort.
Tracing the route to 192.168.3.3
VRF info: (vrf in name/id, vrf out name/id)
1 172.168.123.3 1 msec 71 msec *
R2_spoke#
R2_spoke#show dm
R2_spoke#show dmvpn
Legend: Attrb --> S - Static, D - Dynamic, I - Incomplete
N - NATed, L - Local, X - No Socket
T1 - Route Installed, T2 - Nexthop-override
C - CTS Capable
# Ent --> Number of NHRP entries with same NBMA peer
NHS Status: E --> Expecting Replies, R --> Responding, W --> Waiting
UpDn Time --> Up or Down Time for a Tunnel
==========================================================================
Interface: Tunnel0, IPv4 NHRP Details
Type:Spoke, NHRP Peers:2,
# Ent Peer NBMA Addr Peer Tunnel Add State UpDn Tm Attrb
----- --------------- --------------- ----- -------- -----
1 10.1.14.1 172.168.123.1 UP 00:01:37 S
2 10.1.34.3 172.168.123.3 UP 00:00:48 DT1
172.168.123.3 UP 00:00:48 DT1
总结
阶段一：Hub配置mGRE，Spoke端配置P2P GRE，Spoke到Spoke没有直接的隧道；
阶段二：Hub和Spoke端全部配置mGRE，使用路由协议的方法解决Spoke学到Spoke路由的下一跳问题；
阶段三：Hub和Spoke端全部配置mGRE，使用NHRP解决下一跳解析问题，这样Hub端可以汇总路由，解决了扩展性问题
OSPF的配置案例：
HUB1
R1#show run int tunnel 0
Building configuration...
Current configuration : 301 bytes
!
interface Tunnel0
ip address 10.1.1.1 255.255.255.0
no ip redirects
ip nhrp authentication xuxing
ip nhrp map multicast dynamic
ip nhrp map 10.1.1.2 26.1.1.2
ip nhrp network-id 100
ip nhrp redirect
ip ospf network point-to-multipoint
tunnel source 16.1.1.1
tunnel mode gre multipoint
end
Spoke3
R3#show run int tunnel 0
Building configuration...
Current configuration : 377 bytes
!
interface Tunnel0
ip address 10.1.1.3 255.255.255.0
no ip redirects
ip nhrp authentication xuxing
ip nhrp map multicast 16.1.1.1
ip nhrp map 10.1.1.1 16.1.1.1
! ip nhrp map 10.1.1.2 26.1.1.2
ip nhrp network-id 100
ip nhrp nhs 10.1.1.1
! ip nhrp nhs 10.1.1.2
ip nhrp shortcut
ip ospf network point-to-multipoint
tunnel source 36.1.1.3
tunnel mode gre multipoint
end
R3#
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