summaryrefslogtreecommitdiff
path: root/docs/configexamples/dmvpn-dualhub-dualcloud.rst
blob: eb34d7e8d936b2712b0b42f1c89cb42f63e60699 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
:lastproofread: 2024-02-21

.. _examples-dmvpn-dualhub-dualcloud:

#########################
DMVPN Dual HUB Dual Cloud
#########################

This document is to describe a basic setup to build DVMPN network with two Hubs and two clouds using DMVPN Phase3.
OSPF is used as routing protocol inside DMVPN.

In this example we use VyOS 1.5 as HUBs and Spokes (HUB-1, HUB-2, SPOKE-2, SPOKE-3) and Cisco IOSv 15.5(3)M (SPOKE-1)
as a Spoke.

Network Topology
================

.. image:: /_static/images/dual-hub-DMVPN.png
   :width: 80%
   :align: center
   :alt: DMVPN Network Topology

Configurations
==============

Underlay configuration
______________________

Networks 192.168.X.0/24 are used as LANs for every spoke.

HUB-1

.. code-block:: none

    set interfaces ethernet eth0 address '10.0.0.2/30'
    set protocols static route 0.0.0.0/0 next-hop 10.0.0.1

HUB-2

.. code-block:: none

    set interfaces ethernet eth0 address '10.0.1.2/30'
    set protocols static route 0.0.0.0/0 next-hop 10.0.1.1

Spoke-1

.. code-block:: none

    interface GigabitEthernet0/0
     ip address 10.0.11.2 255.255.255.252
     duplex auto
     speed auto
     media-type rj45
    !
    interface GigabitEthernet0/1
     ip address 192.168.11.1 255.255.255.0
     ip ospf 1 area 0
     duplex auto
     speed auto
     media-type rj45
    !
    ip route 0.0.0.0 0.0.0.0 10.0.11.1

Spoke-2

.. code-block:: none

    set interfaces ethernet eth0 address '10.0.12.2/30'
    set interfaces ethernet eth1 address '192.168.12.1/24'
    set protocols static route 0.0.0.0/0 next-hop 10.0.12.1

Spoke-3

.. code-block:: none

    set interfaces ethernet eth0 address '10.0.13.2/30'
    set interfaces ethernet eth1 address '192.168.13.1/24'
    set protocols static route 0.0.0.0/0 next-hop 10.0.13.1

NHRP configuration
__________________

The next step is to configure the NHRP protocol. In a Dual cloud network, every HUB has to be configured with one GRE
multipoint tunnel interface and every spoke has to be configured with two tunnel interfaces, one tunnel to each hub.
In this example tunnel networks are 10.100.100.0/32 for the first cloud and 10.100.100.0/32 for the second cloud.
But VyOS uses FRR for NHRP, that is why the tunnel address mask must be /32.

HUB-1

.. code-block:: none

    set interfaces tunnel tun100 address '10.100.100.1/32'
    set interfaces tunnel tun100 enable-multicast
    set interfaces tunnel tun100 encapsulation 'gre'
    set interfaces tunnel tun100 ip adjust-mss '1360'
    set interfaces tunnel tun100 mtu '1436'
    set interfaces tunnel tun100 parameters ip key '42'
    set interfaces tunnel tun100 source-interface 'eth0'
    set protocols nhrp tunnel tun100 authentication 'vyos'
    set protocols nhrp tunnel tun100 holdtime '300'
    set protocols nhrp tunnel tun100 multicast 'dynamic'
    set protocols nhrp tunnel tun100 network-id '1'
    set protocols nhrp tunnel tun100 redirect
    set protocols nhrp tunnel tun100 registration-no-unique

HUB-2

.. code-block:: none

    set interfaces tunnel tun101 address '10.100.101.1/32'
    set interfaces tunnel tun101 enable-multicast
    set interfaces tunnel tun101 encapsulation 'gre'
    set interfaces tunnel tun101 ip adjust-mss '1360'
    set interfaces tunnel tun101 mtu '1436'
    set interfaces tunnel tun101 parameters ip key '43'
    set interfaces tunnel tun101 source-interface 'eth0'
    set protocols nhrp tunnel tun101 authentication 'vyos'
    set protocols nhrp tunnel tun101 holdtime '300'
    set protocols nhrp tunnel tun101 multicast 'dynamic'
    set protocols nhrp tunnel tun101 network-id '2'
    set protocols nhrp tunnel tun101 redirect
    set protocols nhrp tunnel tun101 registration-no-unique

Spoke-1

.. code-block:: none

    interface Tunnel100
     ip address 10.100.100.11 255.255.255.0
     no ip redirects
     ip mtu 1436
     ip nhrp authentication vyos
     ip nhrp map multicast 10.0.0.2
     ip nhrp network-id 1
     ip nhrp holdtime 300
     ip nhrp nhs 10.100.100.1 nbma 10.0.0.2
     ip nhrp shortcut
     ip tcp adjust-mss 1360
     tunnel source GigabitEthernet0/0
     tunnel mode gre multipoint
     tunnel key 42
    !
    interface Tunnel101
     ip address 10.100.101.11 255.255.255.0
     no ip redirects
     ip mtu 1436
     ip nhrp authentication vyos
     ip nhrp map multicast 10.0.1.2
     ip nhrp network-id 2
     ip nhrp holdtime 300
     ip nhrp nhs 10.100.101.1 nbma 10.0.1.2
     ip nhrp shortcut
     ip tcp adjust-mss 1360
     tunnel source GigabitEthernet0/0
     tunnel mode gre multipoint
     tunnel key 43


Spoke-2

.. code-block:: none

    set interfaces tunnel tun100 address '10.100.100.12/32'
    set interfaces tunnel tun100 enable-multicast
    set interfaces tunnel tun100 encapsulation 'gre'
    set interfaces tunnel tun100 ip adjust-mss '1360'
    set interfaces tunnel tun100 mtu '1436'
    set interfaces tunnel tun100 parameters ip key '42'
    set interfaces tunnel tun100 source-interface 'eth0'
    set interfaces tunnel tun101 address '10.100.101.12/32'
    set interfaces tunnel tun101 enable-multicast
    set interfaces tunnel tun101 encapsulation 'gre'
    set interfaces tunnel tun101 ip adjust-mss '1360'
    set interfaces tunnel tun101 mtu '1436'
    set interfaces tunnel tun101 parameters ip key '43'
    set interfaces tunnel tun101 source-interface 'eth0'
    set protocols nhrp tunnel tun100 authentication 'vyos'
    set protocols nhrp tunnel tun100 holdtime '300'
    set protocols nhrp tunnel tun100 multicast '10.0.0.2'
    set protocols nhrp tunnel tun100 network-id '1'
    set protocols nhrp tunnel tun100 nhs tunnel-ip dynamic nbma '10.0.0.2'
    set protocols nhrp tunnel tun100 registration-no-unique
    set protocols nhrp tunnel tun100 shortcut
    set protocols nhrp tunnel tun101 authentication 'vyos'
    set protocols nhrp tunnel tun101 holdtime '300'
    set protocols nhrp tunnel tun101 multicast '10.0.1.2'
    set protocols nhrp tunnel tun101 network-id '2'
    set protocols nhrp tunnel tun101 nhs tunnel-ip dynamic nbma '10.0.1.2'
    set protocols nhrp tunnel tun101 registration-no-unique
    set protocols nhrp tunnel tun101 shortcut

Spoke-3

.. code-block:: none

    set protocols nhrp tunnel tun100 authentication 'vyos'
    set protocols nhrp tunnel tun100 holdtime '300'
    set protocols nhrp tunnel tun100 multicast '10.0.0.2'
    set protocols nhrp tunnel tun100 network-id '1'
    set protocols nhrp tunnel tun100 nhs tunnel-ip dynamic nbma '10.0.0.2'
    set protocols nhrp tunnel tun100 registration-no-unique
    set protocols nhrp tunnel tun100 shortcut
    set protocols nhrp tunnel tun101 authentication 'vyos'
    set protocols nhrp tunnel tun101 holdtime '300'
    set protocols nhrp tunnel tun101 multicast '10.0.1.2'
    set protocols nhrp tunnel tun101 network-id '2'
    set protocols nhrp tunnel tun101 nhs tunnel-ip dynamic nbma '10.0.1.2'
    set protocols nhrp tunnel tun101 registration-no-unique
    set protocols nhrp tunnel tun101 shortcut

Overlay configuration
_____________________

The last step is to configure the routing protocol. In this scenario, OSPF was chosen as the dynamic routing protocol.
But you can use iBGP or eBGP. To form fast convergence it is possible to use BFD protocol.


HUB-1

.. code-block:: none

    set protocols ospf interface tun100 area '0'
    set protocols ospf interface tun100 network 'point-to-multipoint'
    set protocols ospf interface tun100 passive disable
    set protocols ospf passive-interface 'default'

HUB-2

.. code-block:: none

    set protocols ospf interface tun101 area '0'
    set protocols ospf interface tun101 network 'point-to-multipoint'
    set protocols ospf interface tun101 passive disable
    set protocols ospf passive-interface 'default'

Spoke-1

.. code-block:: none

    interface Tunnel100
     ip ospf network point-to-multipoint
     ip ospf dead-interval 40
     ip ospf hello-interval 10
     ip ospf 1 area 0
    !
    interface Tunnel101
     ip ospf network point-to-multipoint
     ip ospf dead-interval 40
     ip ospf hello-interval 10
     ip ospf 1 area 0
    !
    router ospf 1
     passive-interface default
     no passive-interface Tunnel100
     no passive-interface Tunnel101

Spoke-2

.. code-block:: none

    set protocols ospf interface eth1 area '0'
    set protocols ospf interface tun100 area '0'
    set protocols ospf interface tun100 network 'point-to-multipoint'
    set protocols ospf interface tun100 passive disable
    set protocols ospf interface tun101 area '0'
    set protocols ospf interface tun101 network 'point-to-multipoint'
    set protocols ospf interface tun101 passive disable
    set protocols ospf passive-interface 'default'

Spoke-3

.. code-block:: none

    set protocols ospf interface eth1 area '0'
    set protocols ospf interface tun100 area '0'
    set protocols ospf interface tun100 network 'point-to-multipoint'
    set protocols ospf interface tun100 passive disable
    set protocols ospf interface tun101 area '0'
    set protocols ospf interface tun101 network 'point-to-multipoint'
    set protocols ospf interface tun101 passive disable
    set protocols ospf passive-interface 'default'

Security configuration
______________________

Tunnels can be encrypted by IPSEC for security.

HUB-1

 .. code-block:: none

    set vpn ipsec esp-group ESP-HUB lifetime '1800'
    set vpn ipsec esp-group ESP-HUB mode 'transport'
    set vpn ipsec esp-group ESP-HUB pfs 'disable'
    set vpn ipsec esp-group ESP-HUB proposal 1 encryption 'aes256'
    set vpn ipsec esp-group ESP-HUB proposal 1 hash 'sha1'
    set vpn ipsec ike-group IKE-HUB key-exchange 'ikev1'
    set vpn ipsec ike-group IKE-HUB lifetime '3600'
    set vpn ipsec ike-group IKE-HUB proposal 1 dh-group '2'
    set vpn ipsec ike-group IKE-HUB proposal 1 encryption 'aes256'
    set vpn ipsec ike-group IKE-HUB proposal 1 hash 'sha1'
    set vpn ipsec interface 'eth0'
    set vpn ipsec profile NHRPVPN authentication mode 'pre-shared-secret'
    set vpn ipsec profile NHRPVPN authentication pre-shared-secret 'secret'
    set vpn ipsec profile NHRPVPN bind tunnel 'tun100'
    set vpn ipsec profile NHRPVPN esp-group 'ESP-HUB'
    set vpn ipsec profile NHRPVPN ike-group 'IKE-HUB'

HUB-2

 .. code-block:: none

    set vpn ipsec esp-group ESP-HUB lifetime '1800'
    set vpn ipsec esp-group ESP-HUB mode 'transport'
    set vpn ipsec esp-group ESP-HUB pfs 'disable'
    set vpn ipsec esp-group ESP-HUB proposal 1 encryption 'aes256'
    set vpn ipsec esp-group ESP-HUB proposal 1 hash 'sha1'
    set vpn ipsec ike-group IKE-HUB key-exchange 'ikev1'
    set vpn ipsec ike-group IKE-HUB lifetime '3600'
    set vpn ipsec ike-group IKE-HUB proposal 1 dh-group '2'
    set vpn ipsec ike-group IKE-HUB proposal 1 encryption 'aes256'
    set vpn ipsec ike-group IKE-HUB proposal 1 hash 'sha1'
    set vpn ipsec interface 'eth0'
    set vpn ipsec profile NHRPVPN authentication mode 'pre-shared-secret'
    set vpn ipsec profile NHRPVPN authentication pre-shared-secret 'secret'
    set vpn ipsec profile NHRPVPN bind tunnel 'tun101'
    set vpn ipsec profile NHRPVPN esp-group 'ESP-HUB'
    set vpn ipsec profile NHRPVPN ike-group 'IKE-HUB'

VyOS Spokes have the same configuration

 .. code-block:: none

    set vpn ipsec esp-group ESP-HUB lifetime '1800'
    set vpn ipsec esp-group ESP-HUB mode 'transport'
    set vpn ipsec esp-group ESP-HUB pfs 'disable'
    set vpn ipsec esp-group ESP-HUB proposal 1 encryption 'aes256'
    set vpn ipsec esp-group ESP-HUB proposal 1 hash 'sha1'
    set vpn ipsec ike-group IKE-HUB key-exchange 'ikev1'
    set vpn ipsec ike-group IKE-HUB lifetime '3600'
    set vpn ipsec ike-group IKE-HUB proposal 1 dh-group '2'
    set vpn ipsec ike-group IKE-HUB proposal 1 encryption 'aes256'
    set vpn ipsec ike-group IKE-HUB proposal 1 hash 'sha1'
    set vpn ipsec interface 'eth0'
    set vpn ipsec profile NHRPVPN authentication mode 'pre-shared-secret'
    set vpn ipsec profile NHRPVPN authentication pre-shared-secret 'secret'
    set vpn ipsec profile NHRPVPN bind tunnel 'tun100'
    set vpn ipsec profile NHRPVPN bind tunnel 'tun101'
    set vpn ipsec profile NHRPVPN esp-group 'ESP-HUB'
    set vpn ipsec profile NHRPVPN ike-group 'IKE-HUB'

SPOKE-1

 .. code-block:: none

    crypto isakmp policy 1
     encr aes 256
     authentication pre-share
     group 2
     lifetime 3600
    crypto isakmp key secret address 0.0.0.0
    !
    !
    crypto ipsec transform-set ESP_TRANSFORMSET esp-aes 256 esp-sha-hmac
     mode transport
    !
    !
    crypto ipsec profile gre_protection
     set security-association lifetime seconds 1800
     set transform-set ESP_TRANSFORMSET
    !
    interface Tunnel100
     tunnel protection ipsec profile gre_protection shared
    !
    interface Tunnel101
     tunnel protection ipsec profile gre_protection shared

Monitoring
==========

All spokes created IPSec tunnels to Hubs, are registered on Hubs using NHRP protocol and formed adjacency in OSPF.

.. code-block:: none

    vyos@HUB-1:~$ show vpn ipsec sa
    Connection                  State    Uptime    Bytes In/Out    Packets In/Out    Remote address    Remote ID    Proposal
    --------------------------  -------  --------  --------------  ----------------  ----------------  -----------  ------------------------
    dmvpn-NHRPVPN-tun100-child  up       6m1s      4K/5K           51/56             10.0.13.2         10.0.13.2    AES_CBC_256/HMAC_SHA1_96
    dmvpn-NHRPVPN-tun100-child  up       6m36s     4K/6K           56/65             10.0.12.2         10.0.12.2    AES_CBC_256/HMAC_SHA1_96
    dmvpn-NHRPVPN-tun100-child  up       8m49s     6K/6K           73/77             10.0.11.2         10.0.11.2    AES_CBC_256/HMAC_SHA1_96

    vyos@HUB-1:~$ show ip nhrp cache
    Iface    Type     Protocol                 NBMA                     Claimed NBMA             Flags  Identity
    tun100   dynamic  10.100.100.12            10.0.12.2                10.0.12.2                 T     10.0.12.2
    tun100   dynamic  10.100.100.13            10.0.13.2                10.0.13.2                 T     10.0.13.2
    tun100   dynamic  10.100.100.11            10.0.11.2                10.0.11.2                 T     10.0.11.2
    tun100   local    10.100.100.1             10.0.0.2                 10.0.0.2                        -

    vyos@HUB-1:~$ show ip ospf neighbor

    Neighbor ID     Pri State           Up Time         Dead Time Address         Interface                        RXmtL RqstL DBsmL
    192.168.11.1      1 Full/DROther    17m01s            36.201s 10.100.100.11   tun100:10.100.100.1                  0     0     0
    192.168.12.1      1 Full/DROther    9m42s             37.443s 10.100.100.12   tun100:10.100.100.1                  0     0     0
    192.168.13.1      1 Full/DROther    9m15s             35.053s 10.100.100.13   tun100:10.100.100.1                  0     0     0


First, we see that LANs are accessible through hubs using OSPF routes.

.. code-block:: none

    SPOKE-1#show ip route
    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, p - overrides from PfR

    Gateway of last resort is 10.0.11.1 to network 0.0.0.0
    .....
          192.168.11.0/24 is variably subnetted, 2 subnets, 2 masks
    C        192.168.11.0/24 is directly connected, GigabitEthernet0/1
    L        192.168.11.1/32 is directly connected, GigabitEthernet0/1
    O     192.168.12.0/24 [110/1002] via 10.100.101.1, 00:14:36, Tunnel101
                          [110/1002] via 10.100.100.1, 00:16:13, Tunnel100
    O     192.168.13.0/24 [110/1002] via 10.100.101.1, 00:14:36, Tunnel101
                          [110/1002] via 10.100.100.1, 00:15:45, Tunnel100


    vyos@SPOKE-2:~$ show ip route
    Codes: K - kernel route, C - connected, L - local, S - static,
           R - RIP, O - OSPF, I - IS-IS, B - BGP, E - EIGRP, N - NHRP,
           T - Table, v - VNC, V - VNC-Direct, A - Babel, F - PBR,
           f - OpenFabric, t - Table-Direct,
           > - selected route, * - FIB route, q - queued, r - rejected, b - backup
           t - trapped, o - offload failure

    ......
    O>* 192.168.11.0/24 [110/3] via 10.100.100.1, tun100 onlink, weight 1, 00:12:36
      *                         via 10.100.101.1, tun101 onlink, weight 1, 00:12:36
    O   192.168.12.0/24 [110/1] is directly connected, eth1, weight 1, 01:24:40
    C>* 192.168.12.0/24 is directly connected, eth1, weight 1, 01:24:43
    L>* 192.168.12.1/32 is directly connected, eth1, weight 1, 01:24:43
    O>* 192.168.13.0/24 [110/3] via 10.100.100.1, tun100 onlink, weight 1, 00:12:36
      *                         via 10.100.101.1, tun101 onlink, weight 1, 00:12:36

After initiating traffic between SPOKES sites, Phase 3 of DMVPN will work.
For instance, traceroute was generated from PC-SPOKE-2 to PC-SPOKE-1

.. code-block:: none

    PC-SPOKE-2 : 192.168.12.2 255.255.255.0 gateway 192.168.12.1

    PC-SPOKE-2> trace 192.168.11.2
    trace to 192.168.11.2, 8 hops max, press Ctrl+C to stop
     1   192.168.12.1   0.558 ms  0.378 ms  0.561 ms
     2   10.100.101.1   1.768 ms  1.158 ms  1.744 ms
     3   10.100.101.11   7.196 ms  4.971 ms  4.793 ms
     4   *192.168.11.2   7.747 ms (ICMP type:3, code:3, Destination port unreachable)

    PC-SPOKE-2> trace 192.168.11.2
    trace to 192.168.11.2, 8 hops max, press Ctrl+C to stop
     1   192.168.12.1   0.562 ms  0.396 ms  0.364 ms
     2   10.100.100.11   4.401 ms  4.399 ms  4.174 ms
     3   *192.168.11.2   3.241 ms (ICMP type:3, code:3, Destination port unreachable)

First trace goes via HUB but the second goes directly from  SPOKE-1 to SPOKE-2.
Now routing tables are changed. LAN networks 192.168.12.0/24 and 192.168.11.0/24 available directly via SPOKES.

.. code-block:: none

    vyos@SPOKE-2:~$ show ip route
    Codes: K - kernel route, C - connected, L - local, S - static,
           R - RIP, O - OSPF, I - IS-IS, B - BGP, E - EIGRP, N - NHRP,
           T - Table, v - VNC, V - VNC-Direct, A - Babel, F - PBR,
           f - OpenFabric, t - Table-Direct,
           > - selected route, * - FIB route, q - queued, r - rejected, b - backup
           t - trapped, o - offload failure

    N>* 192.168.11.0/24 [10/0] via 10.100.100.11, tun100 onlink, weight 1, 00:00:14
    O   192.168.11.0/24 [110/3] via 10.100.100.1, tun100 onlink, weight 1, 00:00:54
                                via 10.100.101.1, tun101 onlink, weight 1, 00:00:54


    SPOKE-1# show ip route next-hop-override
    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, p - overrides from PfR

    Gateway of last resort is 10.0.11.1 to network 0.0.0.0

    O   % 192.168.12.0/24 [110/1002] via 10.100.101.1, 00:24:09, Tunnel101
                          [110/1002] via 10.100.100.1, 00:25:46, Tunnel100
                          [NHO][110/1] via 10.100.100.12, 00:00:03, Tunnel100

NHRP shows shortcuts on Spokes

.. code-block:: none

    vyos@SPOKE-2:~$ show ip nhrp shortcut
    Type     Prefix                   Via                      Identity
    dynamic  192.168.11.0/24          10.100.100.11            10.0.11.2

    SPOKE-1# show ip nhrp shortcut
    10.100.100.12/32 via 10.100.100.12
       Tunnel100 created 00:09:59, expire 00:02:21
       Type: dynamic, Flags: router nhop rib nho
       NBMA address: 10.0.12.2
    192.168.12.0/24 via 10.100.100.12
       Tunnel100 created 00:02:38, expire 00:02:21
       Type: dynamic, Flags: router rib nho
       NBMA address: 10.0.12.2

A new Spoke to Spoke IPSec tunnel is created

.. code-block:: none

    SPOKE-1#show crypto isakmp sa
    IPv4 Crypto ISAKMP SA
    dst             src             state          conn-id status
    10.0.0.2        10.0.11.2       QM_IDLE           1002 ACTIVE
    10.0.12.2       10.0.11.2       QM_IDLE           1004 ACTIVE
    10.0.1.2        10.0.11.2       QM_IDLE           1003 ACTIVE

    vyos@SPOKE-2:~$ show vpn ipsec sa
    Connection                  State    Uptime    Bytes In/Out    Packets In/Out    Remote address    Remote ID    Proposal
    --------------------------  -------  --------  --------------  ----------------  ----------------  -----------  ------------------------
    dmvpn-NHRPVPN-tun100-child  up       7m26s     4K/4K           57/53             10.0.0.2          10.0.0.2     AES_CBC_256/HMAC_SHA1_96
    dmvpn-NHRPVPN-tun100-child  up       11m48s    316B/1K         3/15              10.0.11.2         10.0.11.2    AES_CBC_256/HMAC_SHA1_96
    dmvpn-NHRPVPN-tun101-child  up       5m58s     5K/4K           62/51             10.0.1.2          10.0.1.2     AES_CBC_256/HMAC_SHA1_96

Summary
=======

If one of the Hubs loses connectivity to the Internet, the other Hub will be available and take the main role.
This is a simple example where only one internet connection is used. But in the real world, there can be two
connections to the Internet. In this case, there is a recommendation to build each tunnel via each Internet connection,
choose the main cloud, and manipulate traffic via a routing protocol. It allows the creation failover on link-level
connections too.