Hierarchical DMVPN Phase 3 Introduction to Scalable Designs
Table of Contents
- What is hierarchical DMVPN? ‹
- Configuring multi-region hierarchical DMVPN Phase 3 ‹
- Configuring multi-region scalable DMVPN without direct spoke-to-spoke communication ‹
- Download section ‹
What is hierarchical DMVPN?
Hierarchical DMVPN is a solution designed for scalability in order to connect a very large number of spoke routers in diverse geographical regions. A single hub router can handle a finite number of DMVPN spokes, and hierarchical DMVPN provides a layered mechanism to enable direct site-to-site connectivity but without each spoke connecting to the same hub.
Configuring multi-region hierarchical DMVPN Phase 3
In the following example topology a hierarchical DMVPN network is configured with direct spoke-to-spoke connectivity between each site. The design is purely for educational purposes in order to practice a scalable DMVPN architecture using IOS XE on the Regional Hub and Central Hub routers. The following list highlights several aspects of this example network.
- Between the Regional Hub and the Central Hub there is a DMVPN Phase 1 network using EIGRP. Here, the Regional Hubs act as spoke routers using interface Tunnel100 to establish a point-to-point GRE tunnel with the CHub router.
- Between the Regional Hubs and the Spoke routers R1, R2 and R3 there is a DMVPN Phase 3 network using iBGP. Here, the Regional Hubs use the interface Tunnel200.
- On each Regional Hub prefixes learned through iBGP are redistributed into EIGRP. The command bgp redistribute-internal configured under the BGP process on the Regional Hubs ensures that iBGP prefixes can be redistributed into EIGRP.
- The Spoke routers R1, R2 and R3 prioritize each Regional Hub router. The local preference value 200 is assigned to the default route advertised from Hub1 by issuing the command bgp default local-preference 200 under the BGP process.
Configuration:
CHub
CHub#show run int Gi0/0 | sec int interface GigabitEthernet0/0 description ** Underlay network to Regional DMVPN Hubs ** ip address 172.16.0.1 255.255.255.252 duplex auto speed auto media-type rj45 CHub#show run int Tu100 | sec int interface Tunnel100 description ** DMVPN Phase 1 overlay network ** ip address 10.100.0.1 255.255.255.0 no ip redirects ip nhrp authentication AUTH100 ip nhrp network-id 1000 tunnel source 172.16.0.1 tunnel mode gre multipoint tunnel key 100 CHub#show run all | inc ^interface Tunnel100|ip nhrp map interface Tunnel100 ip nhrp map multicast dynamic CHub#show run | sec ^router router eigrp EXAMPLE-EIGRP ! address-family ipv4 unicast autonomous-system 10 ! af-interface Tunnel100 summary-address 192.168.0.0 255.255.0.0 no split-horizon exit-af-interface ! topology base exit-af-topology network 10.100.0.0 0.0.0.255 eigrp router-id 10.10.10.10 exit-address-family CHub#show run | sec ^ip route ip route 0.0.0.0 0.0.0.0 GigabitEthernet0/0 172.16.0.2
Hub1
Hub1#show run int Gi1 | sec int interface GigabitEthernet1 description ** Underlay network to Spoke Sites ** ip address 172.17.1.1 255.255.255.252 negotiation auto no mop enabled no mop sysid Hub1#show run int Gi2 | sec int interface GigabitEthernet2 description ** Underlay network to Central DMVPN Hubs ** ip address 172.16.1.1 255.255.255.252 negotiation auto no mop enabled no mop sysid Hub1#show run int Tu100 | sec int interface Tunnel100 description ** DMVPN Phase 1 overlay network (CHub) ** ip address 10.100.0.2 255.255.255.0 ip nhrp authentication AUTH100 ip nhrp map 10.100.0.1 172.16.0.1 ip nhrp map multicast 172.16.0.1 ip nhrp network-id 1000 ip nhrp nhs 10.100.0.1 tunnel source GigabitEthernet2 tunnel destination 172.16.0.1 tunnel key 100 Hub1#show run int Tu200 | sec int interface Tunnel200 description ** DMVPN Phase 3 overlay network (Spokes) ** ip address 10.200.0.1 255.255.255.0 no ip redirects ip nhrp authentication AUTH200 ip nhrp network-id 1000 ip nhrp redirect bfd interval 1000 min_rx 1000 multiplier 3 tunnel source 172.17.1.1 tunnel mode gre multipoint tunnel key 200 Hub1#show run | sec ^router eigrp router eigrp EXAMPLE-EIGRP ! address-family ipv4 unicast autonomous-system 10 ! topology base redistribute bgp 65001 route-map RMAP-REDIST-BGP exit-af-topology network 10.100.0.0 0.0.0.255 eigrp router-id 1.1.1.1 exit-address-family Hub1#show run | sec ^route-map route-map RMAP-REDIST-BGP permit 10 set metric 1000 10 100 1 1500 Hub1#show run | sec ^router bgp router bgp 65001 bgp router-id 10.10.10.10 bgp log-neighbor-changes bgp default local-preference 200 bgp redistribute-internal neighbor 10.200.0.5 remote-as 65001 neighbor 10.200.0.5 fall-over bfd neighbor 10.200.0.5 default-originate Hub1#show run | sec ^ip route ip route 172.16.0.0 255.255.0.0 GigabitEthernet2 172.16.1.2 ip route 172.17.0.0 255.255.0.0 GigabitEthernet1 172.17.1.2
Hub2
Hub2#show run int Gi1 | sec int interface GigabitEthernet1 description ** Underlay network to Spoke Sites ** ip address 172.17.2.1 255.255.255.252 negotiation auto no mop enabled no mop sysid Hub2#show run int Gi2 | sec int interface GigabitEthernet2 description ** Underlay network to Central DMVPN Hubs ** ip address 172.16.2.1 255.255.255.252 negotiation auto no mop enabled no mop sysid Hub2#show run int Tu100 | sec int interface Tunnel100 description ** DMVPN Phase 1 overlay network (CHub) ** ip address 10.100.0.3 255.255.255.0 ip nhrp authentication AUTH100 ip nhrp map 10.100.0.1 172.16.0.1 ip nhrp map multicast 172.16.0.1 ip nhrp network-id 1000 ip nhrp nhs 10.100.0.1 tunnel source GigabitEthernet2 tunnel destination 172.16.0.1 tunnel key 100 Hub2#show run int Tu200 | sec int interface Tunnel200 description ** DMVPN Phase 3 overlay network (Spokes) ** ip address 10.200.0.2 255.255.255.0 no ip redirects ip nhrp authentication AUTH200 ip nhrp network-id 1000 ip nhrp redirect bfd interval 1000 min_rx 1000 multiplier 3 tunnel source 172.17.2.1 tunnel mode gre multipoint tunnel key 200 Hub2#show run | sec ^router eigrp router eigrp EXAMPLE-EIGRP ! address-family ipv4 unicast autonomous-system 10 ! topology base redistribute bgp 65001 route-map RMAP-REDIST-BGP exit-af-topology network 10.100.0.0 0.0.0.255 eigrp router-id 2.2.2.2 exit-address-family Hub2#show run | sec ^route-map route-map RMAP-REDIST-BGP permit 10 set metric 1000 10 100 1 1500 Hub2#show run | sec ^router bgp router bgp 65001 bgp router-id 20.20.20.20 bgp log-neighbor-changes bgp default local-preference 175 bgp redistribute-internal neighbor 10.200.0.5 remote-as 65001 neighbor 10.200.0.5 fall-over bfd neighbor 10.200.0.5 default-originate Hub2#show run | sec ^ip route ip route 172.16.0.0 255.255.0.0 GigabitEthernet2 172.16.2.2 ip route 172.17.0.0 255.255.0.0 GigabitEthernet1 172.17.2.2
Hub3
Hub3#show run int Gi1 | sec int interface GigabitEthernet1 description ** Underlay network to Spoke Sites ** ip address 172.17.3.1 255.255.255.252 negotiation auto no mop enabled no mop sysid Hub3#show run int Gi2 | sec int interface GigabitEthernet2 description ** Underlay network to Central DMVPN Hubs ** ip address 172.16.3.1 255.255.255.252 negotiation auto no mop enabled no mop sysid Hub3#show run int Tu100 | sec int interface Tunnel100 description ** DMVPN Phase 1 overlay network (CHub) ** ip address 10.100.0.4 255.255.255.0 ip nhrp authentication AUTH100 ip nhrp map 10.100.0.1 172.16.0.1 ip nhrp map multicast 172.16.0.1 ip nhrp network-id 1000 ip nhrp nhs 10.100.0.1 tunnel source GigabitEthernet2 tunnel destination 172.16.0.1 tunnel key 100 Hub3#show run int Tu200 | sec int interface Tunnel200 description ** DMVPN Phase 3 overlay network (Spokes) ** ip address 10.200.0.3 255.255.255.0 no ip redirects ip nhrp authentication AUTH200 ip nhrp network-id 1000 ip nhrp redirect bfd interval 1000 min_rx 1000 multiplier 3 tunnel source 172.17.3.1 tunnel mode gre multipoint tunnel key 200 Hub3#show run | sec ^router eigrp router eigrp EXAMPLE-EIGRP ! address-family ipv4 unicast autonomous-system 10 ! topology base redistribute bgp 65001 route-map RMAP-REDIST-BGP exit-af-topology network 10.100.0.0 0.0.0.255 eigrp router-id 3.3.3.3 exit-address-family Hub3#show run | sec ^route-map route-map RMAP-REDIST-BGP permit 10 set metric 1000 10 100 1 1500 Hub3#show run | sec ^router bgp router bgp 65001 bgp router-id 30.30.30.30 bgp log-neighbor-changes bgp default local-preference 150 bgp redistribute-internal neighbor 10.200.0.6 remote-as 65001 neighbor 10.200.0.6 fall-over bfd neighbor 10.200.0.6 default-originate neighbor 10.200.0.7 remote-as 65001 neighbor 10.200.0.7 fall-over bfd neighbor 10.200.0.7 default-originate Hub3#show run | sec ^ip route ip route 172.16.0.0 255.255.0.0 GigabitEthernet2 172.16.3.2 ip route 172.17.0.0 255.255.0.0 GigabitEthernet1 172.17.3.2
Hub4
Hub4#show run int Gi1 | sec int interface GigabitEthernet1 description ** Underlay network to Spoke Sites ** ip address 172.17.4.1 255.255.255.252 negotiation auto no mop enabled no mop sysid Hub4#show run int Gi2 | sec int interface GigabitEthernet2 description ** Underlay network to Central DMVPN Hubs ** ip address 172.16.4.1 255.255.255.252 negotiation auto no mop enabled no mop sysid Hub4#show run int Tu100 | sec int interface Tunnel100 description ** DMVPN Phase 1 overlay network (CHub) ** ip address 10.100.0.5 255.255.255.0 ip nhrp authentication AUTH100 ip nhrp map 10.100.0.1 172.16.0.1 ip nhrp map multicast 172.16.0.1 ip nhrp network-id 1000 ip nhrp nhs 10.100.0.1 tunnel source GigabitEthernet2 tunnel destination 172.16.0.1 tunnel key 100 Hub4#show run int Tu200 | sec int interface Tunnel200 description ** DMVPN Phase 3 overlay network (Spokes) ** ip address 10.200.0.4 255.255.255.0 no ip redirects ip nhrp authentication AUTH200 ip nhrp network-id 1000 ip nhrp redirect bfd interval 1000 min_rx 1000 multiplier 3 tunnel source 172.17.4.1 tunnel mode gre multipoint tunnel key 200 Hub4#show run | sec ^router eigrp router eigrp EXAMPLE-EIGRP ! address-family ipv4 unicast autonomous-system 10 ! topology base redistribute bgp 65001 route-map RMAP-REDIST-BGP exit-af-topology network 10.100.0.0 0.0.0.255 eigrp router-id 4.4.4.4 exit-address-family Hub4#show run | sec ^route-map route-map RMAP-REDIST-BGP permit 10 set metric 1000 10 100 1 1500 Hub4#show run | sec ^router bgp router bgp 65001 bgp router-id 40.40.40.40 bgp log-neighbor-changes bgp default local-preference 125 bgp redistribute-internal neighbor 10.200.0.6 remote-as 65001 neighbor 10.200.0.6 fall-over bfd neighbor 10.200.0.6 default-originate neighbor 10.200.0.7 remote-as 65001 neighbor 10.200.0.7 fall-over bfd neighbor 10.200.0.7 default-originate Hub4#show run | sec ^ip route ip route 172.16.0.0 255.255.0.0 GigabitEthernet2 172.16.4.2 ip route 172.17.0.0 255.255.0.0 GigabitEthernet1 172.17.4.2
R1 (Spoke)
R1#show run int Gi0/0 | sec int interface GigabitEthernet0/0 description ** to Host1 ** ip address 192.168.1.2 255.255.255.0 duplex auto speed auto media-type rj45 R1#show run int Gi0/1 | sec int interface GigabitEthernet0/1 description ** to Internet Provider ** ip address 172.17.5.1 255.255.255.252 duplex auto speed auto media-type rj45 R1#show run int Tu200 | sec int interface Tunnel200 description ** DMVPN Phase 3 tunnel overlay (Hub1 + Hub2) ** ip address 10.200.0.5 255.255.255.0 no ip redirects ip nhrp authentication AUTH200 ip nhrp map 10.200.0.1 172.17.1.1 ip nhrp map 10.200.0.2 172.17.2.1 ip nhrp network-id 1000 ip nhrp nhs 10.200.0.1 ip nhrp nhs 10.200.0.2 bfd interval 1000 min_rx 1000 multiplier 3 tunnel source GigabitEthernet0/1 tunnel mode gre multipoint tunnel key 200 R1#show run all | inc interface Tunnel200|ip nhrp shortcut interface Tunnel200 ip nhrp shortcut R1#show run | sec ^router router bgp 65001 template peer-session EXAMPLE-TEMPLATE remote-as 65001 fall-over bfd exit-peer-session ! bgp router-id 1.1.1.1 bgp log-neighbor-changes network 192.168.1.0 neighbor 10.200.0.1 inherit peer-session EXAMPLE-TEMPLATE neighbor 10.200.0.2 inherit peer-session EXAMPLE-TEMPLATE R1#show run | sec ^ip route ip route 172.17.0.0 255.255.0.0 GigabitEthernet0/1 172.17.5.2
R2 (Spoke)
R2#show run int Gi0/0 | sec int interface GigabitEthernet0/0 description ** to Host2 ** ip address 192.168.2.2 255.255.255.0 duplex auto speed auto media-type rj45 R2#show run int Gi0/1 | sec int interface GigabitEthernet0/1 description ** to Internet Provider ** ip address 172.17.6.1 255.255.255.252 duplex auto speed auto media-type rj45 R2#show run int Tu200 | sec int interface Tunnel200 description ** DMVPN Phase 3 tunnel overlay (Hub3 + Hub4) ** ip address 10.200.0.6 255.255.255.0 no ip redirects ip nhrp authentication AUTH200 ip nhrp map 10.200.0.3 172.17.3.1 ip nhrp map 10.200.0.4 172.17.4.1 ip nhrp network-id 1000 ip nhrp nhs 10.200.0.3 ip nhrp nhs 10.200.0.4 bfd interval 1000 min_rx 1000 multiplier 3 tunnel source GigabitEthernet0/1 tunnel mode gre multipoint tunnel key 200 R2#show run all | inc interface Tunnel200|ip nhrp shortcut interface Tunnel200 ip nhrp shortcut R2#show run | sec ^router router bgp 65001 template peer-session EXAMPLE-TEMPLATE remote-as 65001 fall-over bfd exit-peer-session ! bgp router-id 2.2.2.2 bgp log-neighbor-changes network 192.168.2.0 neighbor 10.200.0.3 inherit peer-session EXAMPLE-TEMPLATE neighbor 10.200.0.4 inherit peer-session EXAMPLE-TEMPLATE R2#show run | sec ^ip route ip route 172.17.0.0 255.255.0.0 GigabitEthernet0/1 172.17.6.2
R3 (Spoke)
R3#show run int Gi0/0 | sec int interface GigabitEthernet0/0 description ** to Host3 ** ip address 192.168.3.2 255.255.255.0 duplex auto speed auto media-type rj45 R3#show run int Gi0/1 | sec int interface GigabitEthernet0/1 description ** to Internet Provider ** ip address 172.17.7.1 255.255.255.252 duplex auto speed auto media-type rj45 R3#show run int Tu200 | sec int interface Tunnel200 description ** DMVPN Phase 3 tunnel overlay (Hub3 + Hub4) ** ip address 10.200.0.7 255.255.255.0 no ip redirects ip nhrp authentication AUTH200 ip nhrp map 10.200.0.3 172.17.3.1 ip nhrp map 10.200.0.4 172.17.4.1 ip nhrp network-id 1000 ip nhrp nhs 10.200.0.3 ip nhrp nhs 10.200.0.4 bfd interval 1000 min_rx 1000 multiplier 3 tunnel source GigabitEthernet0/1 tunnel mode gre multipoint tunnel key 200 R3#show run all | inc interface Tunnel200|ip nhrp shortcut interface Tunnel200 ip nhrp shortcut R3#show run | sec ^router router bgp 65001 template peer-session EXAMPLE-TEMPLATE remote-as 65001 fall-over bfd exit-peer-session ! bgp router-id 3.3.3.3 bgp log-neighbor-changes network 192.168.3.0 neighbor 10.200.0.3 inherit peer-session EXAMPLE-TEMPLATE neighbor 10.200.0.4 inherit peer-session EXAMPLE-TEMPLATE R3#show run | sec ^ip route ip route 172.17.0.0 255.255.0.0 GigabitEthernet0/1 172.17.7.2
Host1
Host1#show run int Gi0/0 | sec int interface GigabitEthernet0/0 description ** to Spoke R1 ** ip address 192.168.1.1 255.255.255.0 duplex auto speed auto media-type rj45 Host1#show run | sec ^ip route ip route 0.0.0.0 0.0.0.0 GigabitEthernet0/0 192.168.1.2
Host1#trace 192.168.2.1 probe 1 Type escape sequence to abort. Tracing the route to 192.168.2.1 VRF info: (vrf in name/id, vrf out name/id) 1 192.168.1.2 11 msec 2 10.200.0.1 3 msec 3 10.100.0.1 4 msec « From Site 1 to Site 2 first packet goes through CHub 4 10.100.0.5 7 msec 5 10.200.0.6 33 msec 6 192.168.2.1 35 msec Host1#trace 192.168.2.1 probe 1 Type escape sequence to abort. Tracing the route to 192.168.2.1 VRF info: (vrf in name/id, vrf out name/id) 1 192.168.1.2 1 msec 2 10.200.0.6 3 msec « Second packet goes directly from Site 1 to Site 2 3 192.168.2.1 3 msec Host1#trace 192.168.3.1 probe 1 Type escape sequence to abort. Tracing the route to 192.168.3.1 VRF info: (vrf in name/id, vrf out name/id) 1 192.168.1.2 2 msec 2 10.200.0.1 3 msec 3 10.100.0.1 5 msec « From Site 1 to Site 3 first packet goes through CHub 4 10.100.0.5 5 msec 5 10.200.0.7 6 msec 6 192.168.3.1 9 msec Host1#trace 192.168.3.1 probe 1 Type escape sequence to abort. Tracing the route to 192.168.3.1 VRF info: (vrf in name/id, vrf out name/id) 1 192.168.1.2 1 msec 2 10.200.0.7 3 msec « Second packet goes directly from Site 1 to Site 3 3 192.168.3.1 4 msec Host2#trace 192.168.3.1 probe 1 Type escape sequence to abort. Tracing the route to 192.168.3.1 VRF info: (vrf in name/id, vrf out name/id) 1 192.168.2.2 1 msec 2 10.200.0.3 3 msec « From Site 2 to Site 3 first packet goes through Regional Hub3 3 10.200.0.7 3 msec 4 192.168.3.1 7 msec Host2#trace 192.168.3.1 probe 1 Type escape sequence to abort. Tracing the route to 192.168.3.1 VRF info: (vrf in name/id, vrf out name/id) 1 192.168.2.2 1 msec 2 10.200.0.7 2 msec « Second packet goes directly from Site 2 to Site 3 3 192.168.3.1 4 msec
In the above outputs it is visible that DMVPN Phase 3 spoke-to-spoke direct connectivity works betwen each site. This is possible because the Spoke routers R1, R2 and R3 install shortcut routes into their routing tables through NHRP. The following outputs show these shortcut routes.
R1#show ip route nhrp | beg Ga Gateway of last resort is 10.200.0.1 to network 0.0.0.0 10.0.0.0/8 is variably subnetted, 4 subnets, 2 masks H 10.200.0.6/32 is directly connected, 00:04:05, Tunnel200 H 10.200.0.7/32 is directly connected, 00:02:54, Tunnel200 H 192.168.2.0/24 [250/255] via 10.200.0.6, 00:04:05, Tunnel200 « NHRP route to Site 2 installed on Site 1 Spoke R1 H 192.168.3.0/24 [250/255] via 10.200.0.7, 00:02:54, Tunnel200 R1#show ip nhrp brief **************************************************************************** NOTE: Link-Local, No-socket and Incomplete entries are not displayed **************************************************************************** Legend: Type --> S - Static, D - Dynamic Flags --> u - unique, r - registered, e - temporary, c - claimed a - authoritative, t - route ============================================================================ Intf NextHop Address NBMA Address Target Network T/Flag -------- ------------------------------------------- ------ ---------------- Tu200 10.200.0.1 172.17.1.1 10.200.0.1/32 S/ Tu200 10.200.0.2 172.17.2.1 10.200.0.2/32 S/ Tu200 10.200.0.6 172.17.6.1 192.168.2.0/24 D/t « Dynamic routes installed in NHRP cache and in routing table 10.200.0.6/32 D/t Tu200 10.200.0.7 172.17.7.1 192.168.3.0/24 D/t 10.200.0.7/32 D/t R2#show ip route nhrp | beg Ga Gateway of last resort is 10.200.0.3 to network 0.0.0.0 10.0.0.0/8 is variably subnetted, 4 subnets, 2 masks H 10.200.0.5/32 is directly connected, 00:06:08, Tunnel200 H 10.200.0.7/32 is directly connected, 00:03:30, Tunnel200 H 192.168.1.0/24 [250/255] via 10.200.0.5, 00:06:08, Tunnel200 H 192.168.3.0/24 [250/255] via 10.200.0.7, 00:03:30, Tunnel200
An important aspect of this design is the NHRP message exchange. With DMVPN Phase 2 and Phase 3 the NHRP Resolution Requests are forwarded by the Hub router to the destination Spoke. This also happens in the current example topology, the Regional Hub and the CHub router forward the NHRP Resolution Requests, and eventually the destination Spoke directly replies to the originator Spoke.
The DMVPN Phase 3 Redirect message (Traffic Indication) is originated by the Regional Hub routers and sent to the Spokes. This is shown in the following packet capture.
Furthermore, the following outputs provide information about the routing implemented with this example topology. Note that the DMVPN Phase 1 cloud uses EIGRP so multicast mapping needs to be configured. The DMVPN Phase 3 network's iBGP routes appear as EIGRP external routes. And in fact, the CHub router only advertises a single summary route to the Regional Hub routers.
Hub1#show ip route | beg Ga Gateway of last resort is not set 10.0.0.0/8 is variably subnetted, 4 subnets, 2 masks C 10.100.0.0/24 is directly connected, Tunnel100 L 10.100.0.2/32 is directly connected, Tunnel100 C 10.200.0.0/24 is directly connected, Tunnel200 L 10.200.0.1/32 is directly connected, Tunnel200 172.16.0.0/16 is variably subnetted, 3 subnets, 3 masks S 172.16.0.0/16 [1/0] via 172.16.1.2, GigabitEthernet2 C 172.16.1.0/30 is directly connected, GigabitEthernet2 L 172.16.1.1/32 is directly connected, GigabitEthernet2 172.17.0.0/16 is variably subnetted, 3 subnets, 3 masks S 172.17.0.0/16 [1/0] via 172.17.1.2, GigabitEthernet1 C 172.17.1.0/30 is directly connected, GigabitEthernet1 L 172.17.1.1/32 is directly connected, GigabitEthernet1 D 192.168.0.0/16 [90/102451200] via 10.100.0.1, 01:21:17, Tunnel100 « EIGRP summary route originated by CHub B 192.168.1.0/24 [200/0] via 10.200.0.5, 01:36:56 « DMVPN Phase 3 Site-specific prefix Hub3#show ip route | beg Ga Gateway of last resort is not set 10.0.0.0/8 is variably subnetted, 4 subnets, 2 masks C 10.100.0.0/24 is directly connected, Tunnel100 L 10.100.0.4/32 is directly connected, Tunnel100 C 10.200.0.0/24 is directly connected, Tunnel200 L 10.200.0.3/32 is directly connected, Tunnel200 172.16.0.0/16 is variably subnetted, 3 subnets, 3 masks S 172.16.0.0/16 [1/0] via 172.16.3.2, GigabitEthernet2 C 172.16.3.0/30 is directly connected, GigabitEthernet2 L 172.16.3.1/32 is directly connected, GigabitEthernet2 172.17.0.0/16 is variably subnetted, 3 subnets, 3 masks S 172.17.0.0/16 [1/0] via 172.17.3.2, GigabitEthernet1 C 172.17.3.0/30 is directly connected, GigabitEthernet1 L 172.17.3.1/32 is directly connected, GigabitEthernet1 D 192.168.0.0/16 [90/102451200] via 10.100.0.1, 01:22:01, Tunnel100 B 192.168.2.0/24 [200/0] via 10.200.0.6, 01:36:37 B 192.168.3.0/24 [200/0] via 10.200.0.7, 01:36:37 CHub#show dmvpn | beg Int Interface: Tunnel100, IPv4 NHRP Details Type:Hub, NHRP Peers:4, # Ent Peer NBMA Addr Peer Tunnel Add State UpDn Tm Attrb ----- --------------- --------------- ----- -------- ----- 1 172.16.1.1 10.100.0.2 UP 01:22:20 D « Regional Hubs are registered with the CHub 1 172.16.2.1 10.100.0.3 UP 01:21:46 D 1 172.16.3.1 10.100.0.4 UP 01:22:22 D 1 172.16.4.1 10.100.0.5 UP 01:22:19 D CHub#show ip route eigrp | beg Ga « Site prefixes are received on CHub router Gateway of last resort is 172.16.0.2 to network 0.0.0.0 D 192.168.0.0/16 is a summary, 01:23:51, Null0 D EX 192.168.1.0/24 [170/76851200] via 10.100.0.3, 01:23:12, Tunnel100 [170/76851200] via 10.100.0.2, 01:23:12, Tunnel100 D EX 192.168.2.0/24 [170/76851200] via 10.100.0.5, 01:23:49, Tunnel100 [170/76851200] via 10.100.0.4, 01:23:49, Tunnel100 D EX 192.168.3.0/24 [170/76851200] via 10.100.0.5, 01:23:49, Tunnel100 [170/76851200] via 10.100.0.4, 01:23:49, Tunnel100 Hub1#show dmvpn | beg Int Interface: Tunnel100, IPv4 NHRP Details Type:Spoke, NHRP Peers:1, # Ent Peer NBMA Addr Peer Tunnel Add State UpDn Tm Attrb ----- --------------- --------------- ----- -------- ----- 1 172.16.0.1 10.100.0.1 UP 01:23:10 S « Regional Hub is spoke of CHub Interface: Tunnel200, IPv4 NHRP Details Type:Hub, NHRP Peers:1, # Ent Peer NBMA Addr Peer Tunnel Add State UpDn Tm Attrb ----- --------------- --------------- ----- -------- ----- 1 172.17.5.1 10.200.0.5 UP 01:38:59 D « Regional Hub is hub of Spoke routers R1#show ip route bgp | beg Ga Gateway of last resort is 200.0.0.1 to network 0.0.0.0 B* 0.0.0.0/0 [200/0] via 200.0.0.1, 00:54:09 « Spoke receives single BGP default route from Regional Hub R1#show ip route bgp | beg Ga Gateway of last resort is 10.200.0.1 to network 0.0.0.0 B* 0.0.0.0/0 [200/0] via 10.200.0.1, 01:40:09 « Spoke receives single BGP default route from Regional Hub R1#show ip bgp | beg Ne Network Next Hop Metric LocPrf Weight Path * i 0.0.0.0 10.200.0.2 0 175 0 i « Spoke receives multiple BGP default routes with different local preference *>i 10.200.0.1 0 200 0 i *> 192.168.1.0 0.0.0.0 0 32768 i
The above outputs show why this design is scalable. Namely, not all spoke routers need to be connected to each Regional Hub router in order to have direct spoke-to-spoke connectivity. For example, Spoke R1 is only connected to Hub1, but can still reach Site 2 and Site 3 with a direct tunnel using DMVPN Phase 3.
Configuring multi-region scalable DMVPN without direct spoke-to-spoke communication
In the following example topology two regional DMVPN networks are connected with a backbone transport link. The design configured in this scenario is intended as a study note for informational purposes only and to practice OSPFv3, DMVPN with iBGP, redistribution, and route filtering.
Within each region DMVPN Phase 3 is configured, so there is direct spoke-to-spoke communication between Site 2 and Site 3. But inter-regional traffic must transit the backbone cloud between Datacenter 1 and 2. The following list highlights several aspects of this example scenario.
- The Datacenters share IPv4 routes using OSPFv3. Datacenter 1 is in OSPF area 1, DC 2 is in area 2, the backbone transport is in area 0. OSPFv3 route filtering is configured on the GW devices so only Spoke Site routes are advertised into each DC.
- Site prefixes are learned through each DMVPN cloud using iBGP. However, in order to redistribute iBGP routes into OSPFv3 on the hub routers the command bgp redistribute-internal is added under the BGP process.
- Each hub router only advertises a single default route through iBGP. To assign a different priority for each hub router the local preference value of the default route is adjusted with the bgp default local-preference 200 example command taken from Hub1.
- Each hub router learns Site-specific prefixes through iBGP and also through OSPFv3. The OSPF Administrative Distance (AD) is increased so that the hub routers always prefer iBGP when a prefix is originated from the local DMVPN cloud. This enables the NHRP Redirect message and direct spoke-to-spoke communication for traffic that stays within a single region (intra-regional).
Configuration:
Hub1
Hub1#show run int Gi0/0 | sec int interface GigabitEthernet0/0 description ** to Internet Provider ** ip address 172.16.1.2 255.255.255.252 duplex auto speed auto media-type rj45 Hub1#show run int Gi0/1 | sec int interface GigabitEthernet0/1 description ** to GW1 ** ip address 192.168.10.2 255.255.255.0 duplex auto speed auto media-type rj45 ipv6 address FE80::2 link-local ospfv3 10 ipv4 area 1 ospfv3 10 ipv4 priority 0 Hub1#show run int Tu10 | sec int interface Tunnel10 description ** DMVPN Phase 3 tunnel overlay (left side cloud) ** ip address 10.10.0.1 255.255.255.0 no ip redirects ip nhrp authentication AUTH10 ip nhrp network-id 100 ip nhrp redirect bfd interval 1000 min_rx 1000 multiplier 3 tunnel source 172.16.1.2 tunnel mode gre multipoint tunnel key 10 Hub1#show run | sec ^router ospf router ospfv3 10 router-id 1.1.1.1 ! address-family ipv4 unicast redistribute bgp 65001 route-map RM-REDIST-DMVPN distance 210 exit-address-family Hub1#show run | sec ^route-map route-map RM-REDIST-DMVPN permit 10 match ip address prefix-list PL-REDIST-DMVPN Hub1#show run | sec ^ip prefix ip prefix-list PL-REDIST-DMVPN seq 5 permit 192.168.1.0/24 Hub1#show run | sec ^router bgp router bgp 65001 bgp router-id 10.10.10.10 bgp log-neighbor-changes bgp default local-preference 200 bgp redistribute-internal neighbor 10.10.0.3 remote-as 65001 neighbor 10.10.0.3 fall-over bfd neighbor 10.10.0.3 default-originate Hub1#show run | sec ^ip route ip route 0.0.0.0 0.0.0.0 GigabitEthernet0/0 172.16.1.1 Hub1#show run | sec ^ipv6 uni ipv6 unicast-routing
Hub2
Hub2#show run int Gi0/0 | sec int interface GigabitEthernet0/0 description ** to Internet Provider ** ip address 172.16.2.2 255.255.255.252 duplex auto speed auto media-type rj45 Hub2#show run int Gi0/1 | sec int interface GigabitEthernet0/1 description ** to GW1 ** ip address 192.168.10.3 255.255.255.0 duplex auto speed auto media-type rj45 ipv6 address FE80::3 link-local ospfv3 10 ipv4 area 1 ospfv3 10 ipv4 priority 0 Hub2#show run int Tu10 | sec int interface Tunnel10 description ** DMVPN Phase 3 tunnel overlay (left side cloud) ** ip address 10.10.0.2 255.255.255.0 no ip redirects ip nhrp authentication AUTH10 ip nhrp network-id 100 ip nhrp redirect bfd interval 1000 min_rx 1000 multiplier 3 tunnel source 172.16.2.2 tunnel mode gre multipoint tunnel key 10 Hub2#show run | sec ^router ospf router ospfv3 10 router-id 2.2.2.2 ! address-family ipv4 unicast redistribute bgp 65001 metric 2 route-map RM-REDIST-DMVPN distance 210 exit-address-family Hub2#show run | sec ^route-map route-map RM-REDIST-DMVPN permit 10 match ip address prefix-list PL-REDIST-DMVPN Hub2#show run | sec ^ip prefix ip prefix-list PL-REDIST-DMVPN seq 5 permit 192.168.1.0/24 Hub2#show run | sec ^router bgp router bgp 65001 bgp router-id 20.20.20.20 bgp log-neighbor-changes bgp default local-preference 150 bgp redistribute-internal neighbor 10.10.0.3 remote-as 65001 neighbor 10.10.0.3 fall-over bfd neighbor 10.10.0.3 default-originate Hub2#show run | sec ^ip route ip route 0.0.0.0 0.0.0.0 GigabitEthernet0/0 172.16.2.1 Hub2#show run | sec ^ipv6 uni ipv6 unicast-routing
Hub3
Hub3#show run int Gi0/0 | sec int interface GigabitEthernet0/0 description ** to Internet Provider ** ip address 172.16.3.2 255.255.255.252 duplex auto speed auto media-type rj45 Hub3#show run int Gi0/1 | sec int interface GigabitEthernet0/1 description ** to GW2 ** ip address 192.168.20.2 255.255.255.0 duplex auto speed auto media-type rj45 ipv6 address FE80::2 link-local ospfv3 10 ipv4 area 2 ospfv3 10 ipv4 priority 0 Hub3#show run int Tu10 | sec int interface Tunnel10 description ** DMVPN Phase 3 tunnel overlay (right side cloud) ** ip address 10.20.0.1 255.255.255.0 no ip redirects ip nhrp authentication AUTH20 ip nhrp network-id 200 ip nhrp redirect bfd interval 1000 min_rx 1000 multiplier 3 tunnel source 172.16.3.2 tunnel mode gre multipoint tunnel key 20 Hub3#show run | sec ^router ospf router ospfv3 10 router-id 3.3.3.3 ! address-family ipv4 unicast redistribute bgp 65002 route-map RMAP-REDIST-DMVPN distance 210 exit-address-family Hub3#show run | sec ^route-map route-map RMAP-REDIST-DMVPN permit 10 match ip address prefix-list PL-REDIST-DMVPN Hub3#show run | sec ^ip prefix ip prefix-list PL-REDIST-DMVPN seq 5 permit 192.168.2.0/24 ip prefix-list PL-REDIST-DMVPN seq 10 permit 192.168.3.0/24 Hub3#show run | sec ^router bgp router bgp 65002 bgp router-id 10.10.10.10 bgp log-neighbor-changes bgp default local-preference 200 bgp redistribute-internal neighbor 10.20.0.3 remote-as 65002 neighbor 10.20.0.3 fall-over bfd neighbor 10.20.0.3 default-originate neighbor 10.20.0.4 remote-as 65002 neighbor 10.20.0.4 fall-over bfd neighbor 10.20.0.4 default-originate Hub3#show run | sec ^ip route ip route 0.0.0.0 0.0.0.0 GigabitEthernet0/0 172.16.3.1 Hub3#show run | sec ^ipv6 uni ipv6 unicast-routing
Hub4
Hub4#show run int Gi0/0 | sec int interface GigabitEthernet0/0 description ** to Internet Provider ** ip address 172.16.4.2 255.255.255.252 duplex auto speed auto media-type rj45 Hub4#show run int Gi0/1 | sec int interface GigabitEthernet0/1 description ** to GW2 ** ip address 192.168.20.3 255.255.255.0 duplex auto speed auto media-type rj45 ipv6 address FE80::3 link-local ospfv3 10 ipv4 area 2 ospfv3 10 ipv4 priority 0 Hub4#show run int Tu10 | sec int interface Tunnel10 description ** DMVPN Phase 3 tunnel overlay (right side cloud) ** ip address 10.20.0.2 255.255.255.0 no ip redirects ip nhrp authentication AUTH20 ip nhrp network-id 200 ip nhrp redirect bfd interval 1000 min_rx 1000 multiplier 3 tunnel source 172.16.4.2 tunnel mode gre multipoint tunnel key 20 Hub4#show run | sec ^router ospf router ospfv3 10 router-id 4.4.4.4 ! address-family ipv4 unicast redistribute bgp 65002 metric 2 route-map RMAP-REDIST-DMVPN distance 210 exit-address-family Hub4#show run | sec ^route-map route-map RMAP-REDIST-DMVPN permit 10 match ip address prefix-list PL-REDIST-DMVPN Hub4#show run | sec ^ip prefix ip prefix-list PL-REDIST-DMVPN seq 5 permit 192.168.2.0/24 ip prefix-list PL-REDIST-DMVPN seq 10 permit 192.168.3.0/24 Hub4#show run | sec ^router bgp router bgp 65002 bgp router-id 20.20.20.20 bgp log-neighbor-changes bgp default local-preference 150 bgp redistribute-internal neighbor 10.20.0.3 remote-as 65002 neighbor 10.20.0.3 fall-over bfd neighbor 10.20.0.3 default-originate neighbor 10.20.0.4 remote-as 65002 neighbor 10.20.0.4 fall-over bfd neighbor 10.20.0.4 default-originate Hub4#show run | sec ^ip route ip route 0.0.0.0 0.0.0.0 GigabitEthernet0/0 172.16.4.1 Hub4#show run | sec ^ipv6 uni ipv6 unicast-routing
R1 (Spoke)
R1#show run int Gi0/0 | sec int interface GigabitEthernet0/0 description ** to Host1 ** ip address 192.168.1.2 255.255.255.0 duplex auto speed auto media-type rj45 R1#show run int Gi0/1 | sec int interface GigabitEthernet0/1 description ** to Internet Provider ** ip address 172.16.5.2 255.255.255.252 duplex auto speed auto media-type rj45 R1#show run int Tu10 | sec int interface Tunnel10 description ** DMVPN Phase 3 tunnel overlay (left side cloud) ** ip address 10.10.0.3 255.255.255.0 no ip redirects ip nhrp authentication AUTH10 ip nhrp map 10.10.0.1 172.16.1.2 ip nhrp map 10.10.0.2 172.16.2.2 ip nhrp network-id 100 ip nhrp nhs 10.10.0.1 ip nhrp nhs 10.10.0.2 bfd interval 1000 min_rx 1000 multiplier 3 tunnel source GigabitEthernet0/1 tunnel mode gre multipoint tunnel key 10 R1#show run | sec ^router router bgp 65001 template peer-session EXAMPLE-TEMPLATE remote-as 65001 fall-over bfd exit-peer-session ! bgp router-id 1.1.1.1 bgp log-neighbor-changes network 192.168.1.0 neighbor 10.10.0.1 inherit peer-session EXAMPLE-TEMPLATE neighbor 10.10.0.2 inherit peer-session EXAMPLE-TEMPLATE R1#show run | sec ^ip route ip route 172.16.0.0 255.255.0.0 GigabitEthernet0/1 172.16.5.1
R2 (Spoke)
R2#show run int Gi0/0 | sec int interface GigabitEthernet0/0 description ** to Host2 ** ip address 192.168.2.2 255.255.255.0 duplex auto speed auto media-type rj45 R2#show run int Gi0/1 | sec int interface GigabitEthernet0/1 description ** to Internet Provider ** ip address 172.16.6.2 255.255.255.252 duplex auto speed auto media-type rj45 R2#show run int Tu10 | sec int interface Tunnel10 description ** DMVPN Phase 3 tunnel overlay (right side cloud) ** ip address 10.20.0.3 255.255.255.0 no ip redirects ip nhrp authentication AUTH20 ip nhrp map 10.20.0.2 172.16.4.2 ip nhrp map 10.20.0.1 172.16.3.2 ip nhrp network-id 200 ip nhrp nhs 10.20.0.1 ip nhrp nhs 10.20.0.2 bfd interval 1000 min_rx 1000 multiplier 3 tunnel source GigabitEthernet0/1 tunnel mode gre multipoint tunnel key 20 R2#show run | sec ^router router bgp 65002 template peer-session EXAMPLE-TEMPLATE remote-as 65002 fall-over bfd exit-peer-session ! bgp router-id 1.1.1.1 bgp log-neighbor-changes network 192.168.2.0 neighbor 10.20.0.1 inherit peer-session EXAMPLE-TEMPLATE neighbor 10.20.0.2 inherit peer-session EXAMPLE-TEMPLATE R2#show run | sec ^ip route ip route 172.16.0.0 255.255.0.0 GigabitEthernet0/1 172.16.6.1
R3 (Spoke)
R3#show run int Gi0/0 | sec int interface GigabitEthernet0/0 description ** to Host3 ** ip address 192.168.3.2 255.255.255.0 duplex auto speed auto media-type rj45 R3#show run int Gi0/1 | sec int interface GigabitEthernet0/1 description ** to Internet Provider ** ip address 172.16.7.2 255.255.255.252 duplex auto speed auto media-type rj45 R3#show run int Tu10 | sec int interface Tunnel10 description ** DMVPN Phase 3 tunnel overlay (right side cloud) ** ip address 10.20.0.4 255.255.255.0 no ip redirects ip nhrp authentication AUTH20 ip nhrp map 10.20.0.2 172.16.4.2 ip nhrp map 10.20.0.1 172.16.3.2 ip nhrp network-id 200 ip nhrp nhs 10.20.0.1 ip nhrp nhs 10.20.0.2 bfd interval 1000 min_rx 1000 multiplier 3 tunnel source GigabitEthernet0/1 tunnel mode gre multipoint tunnel key 20 R3#show run | sec ^router router bgp 65002 template peer-session EXAMPLE-TEMPLATE remote-as 65002 fall-over bfd exit-peer-session ! bgp router-id 2.2.2.2 bgp log-neighbor-changes network 192.168.3.0 neighbor 10.20.0.1 inherit peer-session EXAMPLE-TEMPLATE neighbor 10.20.0.2 inherit peer-session EXAMPLE-TEMPLATE R3#show run | sec ^ip route ip route 172.16.0.0 255.255.0.0 GigabitEthernet0/1 172.16.7.1
GW1
GW1#show run int Gi0/0 | sec int interface GigabitEthernet0/0 description ** to DMVPN Hub routers ** ip address 192.168.10.1 255.255.255.0 duplex auto speed auto media-type rj45 ipv6 address FE80::1 link-local ospfv3 10 ipv4 area 1 ospfv3 10 ipv4 priority 100 GW1#show run int Gi0/1 | sec int interface GigabitEthernet0/1 description ** to Backbone Transport - GW2 ** ip address 172.16.100.1 255.255.255.252 duplex auto speed auto media-type rj45 ipv6 address FE80::1 link-local ospfv3 network point-to-point ospfv3 10 ipv4 area 0 GW1#show run | sec ^router router ospfv3 10 router-id 10.10.10.10 ! address-family ipv4 unicast area 0 filter-list prefix PL-OSPF-FILTER out exit-address-family GW1#show run | sec ^ip prefix ip prefix-list PL-OSPF-FILTER seq 5 permit 192.168.2.0/24 ip prefix-list PL-OSPF-FILTER seq 10 permit 192.168.3.0/24 GW1#show run | sec ^ipv6 uni ipv6 unicast-routing
GW2
GW2#show run int Gi0/0 | sec int interface GigabitEthernet0/0 description ** to DMVPN Hub routers ** ip address 192.168.20.1 255.255.255.0 duplex auto speed auto media-type rj45 ipv6 address FE80::1 link-local ospfv3 10 ipv4 area 2 ospfv3 10 ipv4 priority 100 GW2#show run int Gi0/1 | sec int interface GigabitEthernet0/1 description ** to Backbone Transport - GW2 ** ip address 172.16.100.2 255.255.255.252 duplex auto speed auto media-type rj45 ipv6 address FE80::2 link-local ospfv3 network point-to-point ospfv3 10 ipv4 area 0 GW2#show run | sec ^router router ospfv3 10 router-id 20.20.20.20 ! address-family ipv4 unicast area 0 filter-list prefix PL-OSPF-FILTER out exit-address-family GW2#show run | sec ^ip prefix ip prefix-list PL-OSPF-FILTER seq 5 permit 192.168.1.0/24 GW2#show run | sec ^ipv6 uni ipv6 unicast-routing
Host1
Host1#show run int Gi0/0 | sec int interface GigabitEthernet0/0 description ** to Spoke R1 ** ip address 192.168.1.1 255.255.255.0 duplex auto speed auto media-type rj45 Host1#show run | sec ^ip route ip route 0.0.0.0 0.0.0.0 GigabitEthernet0/0 192.168.1.2
Hub1#show dmvpn | beg Int Interface: Tunnel10, IPv4 NHRP Details Type:Hub, NHRP Peers:1, # Ent Peer NBMA Addr Peer Tunnel Add State UpDn Tm Attrb ----- --------------- --------------- ----- -------- ----- 1 172.16.5.2 10.10.0.3 UP 02:49:08 D « Spoke R1 is registered with Hub1 Hub3#show dmvpn | beg Int Interface: Tunnel10, IPv4 NHRP Details Type:Hub, NHRP Peers:2, # Ent Peer NBMA Addr Peer Tunnel Add State UpDn Tm Attrb ----- --------------- --------------- ----- -------- ----- 1 172.16.6.2 10.20.0.3 UP 02:49:46 D « Spokes R2 and R3 are registered with Hub2 1 172.16.7.2 10.20.0.4 UP 02:49:42 D R1#show ip route bgp | beg Ga Gateway of last resort is 10.10.0.1 to network 0.0.0.0 B* 0.0.0.0/0 [200/0] via 10.10.0.1, 02:48:17 « Spoke R1 prefers default route from Hub1 R1#show ip bgp | beg Ne Network Next Hop Metric LocPrf Weight Path *>i 0.0.0.0 10.10.0.1 0 200 0 i « Local preference value 200 makes this the preferred default route * i 10.10.0.2 0 150 0 i *> 192.168.1.0 0.0.0.0 0 32768 i Host3#trace 192.168.1.1 probe 1 Type escape sequence to abort. Tracing the route to 192.168.1.1 VRF info: (vrf in name/id, vrf out name/id) 1 192.168.3.2 1 msec 2 10.20.0.1 47 msec 3 192.168.20.1 47 msec 4 172.16.100.1 52 msec « Inter-regional traffic goes through backbone transport 5 192.168.10.2 54 msec 6 10.10.0.3 100 msec 7 192.168.1.1 102 msec Host3#trace 192.168.2.1 probe 1 Type escape sequence to abort. Tracing the route to 192.168.2.1 VRF info: (vrf in name/id, vrf out name/id) 1 192.168.3.2 2 msec 2 10.20.0.3 45 msec « Intra-regional traffic uses direct spoke-to-spoke 3 192.168.2.1 45 msec R3#show ip route nhrp | beg Ga Gateway of last resort is 10.20.0.1 to network 0.0.0.0 10.0.0.0/8 is variably subnetted, 3 subnets, 2 masks H 10.20.0.3/32 is directly connected, 00:00:13, Tunnel10 H 192.168.2.0/24 [250/255] via 10.20.0.3, 00:00:13, Tunnel10 « NHRP direct spoke-to-spoke route installed in Spoke R3 RIB Hub3#show ip route ospfv3 | beg Ga Gateway of last resort is 172.16.3.1 to network 0.0.0.0 O E2 192.168.1.0/24 [210/1] via 192.168.20.1, 02:49:44, GigabitEthernet0/1 « Region 2 Hub learns Region 1 DMVPN prefix through OSPF Hub1#show ip route | beg Ga Gateway of last resort is 172.16.1.1 to network 0.0.0.0 S* 0.0.0.0/0 [1/0] via 172.16.1.1, GigabitEthernet0/0 10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks C 10.10.0.0/24 is directly connected, Tunnel10 L 10.10.0.1/32 is directly connected, Tunnel10 172.16.0.0/16 is variably subnetted, 2 subnets, 2 masks C 172.16.1.0/30 is directly connected, GigabitEthernet0/0 L 172.16.1.2/32 is directly connected, GigabitEthernet0/0 B 192.168.1.0/24 [200/0] via 10.10.0.3, 02:49:59 « iBGP route preferred because OSPF has less preferred AD 210 O E2 192.168.2.0/24 [210/1] via 192.168.10.1, 02:49:53, GigabitEthernet0/1 O E2 192.168.3.0/24 [210/1] via 192.168.10.1, 02:49:53, GigabitEthernet0/1 192.168.10.0/24 is variably subnetted, 2 subnets, 2 masks C 192.168.10.0/24 is directly connected, GigabitEthernet0/1 L 192.168.10.2/32 is directly connected, GigabitEthernet0/1 Hub1#show ospfv3 database external 192.168.1.0 OSPFv3 10 address-family ipv4 (router-id 1.1.1.1) Type-5 AS External Link States LS age: 1080 LS Type: AS External Link Link State ID: 0 Advertising Router: 1.1.1.1 LS Seq Number: 80000006 Checksum: 0x8107 Length: 32 Prefix Address: 192.168.1.0 Prefix Length: 24, Options: None Metric Type: 2 (Larger than any link state path) Metric: 1 LS age: 1066 LS Type: AS External Link Link State ID: 0 Advertising Router: 2.2.2.2 « Hub2 also advertises Region 1 DMVPN prefix via OSPFv3 LS Seq Number: 80000006 Checksum: 0x691A Length: 32 Prefix Address: 192.168.1.0 Prefix Length: 24, Options: None Metric Type: 2 (Larger than any link state path) Metric: 2 Hub1#show ip protocols | sec ospf Routing Protocol is "ospfv3 10" Outgoing update filter list for all interfaces is not set Incoming update filter list for all interfaces is not set Router ID 1.1.1.1 Autonomous system boundary router Number of areas: 1 normal, 0 stub, 0 nssa Interfaces (Area 1): GigabitEthernet0/1 Redistributing: bgp 65001 Maximum path: 4 Routing Information Sources: Gateway Distance Last Update 3.3.3.3 210 03:02:34 2.2.2.2 210 03:02:34 Distance: (default is 210) « Hub1 assigns AD 210 to OSPF routes
Additionally, to speed up the failure detection between hub-and-spoke routers BFD is configured together with BGP. This ensures an improved switchover time to a backup Next-Hop Server (to backup hub router) in the event of a network outage. The following output shows that BGP and NHRP are client processes of BFD.
R1#show bfd summary client Client Session Up Down BGP 2 2 0 CEF 2 2 0 NHRP 2 2 0 Total 2 2 0 R1#show bfd neighbors IPv4 Sessions NeighAddr LD/RD RH/RS State Int 10.10.0.1 2/1 Up Up Tu10 10.10.0.2 1/1 Up Up Tu10