LAB 1: Configure DMVPN
Task 1: Configure DMVPN Initial Configuration
Step 1: In the configuration mode of router configure by following command
R1: interface FastEthernet0/0 //creating Active interface ip address 172.16.1.2 255.255.255.252 //Physical/Public/NBMA Address provided by ISP no shutdown interface loopback 1 ip address 11.11.11.11 255.255.255.0 exit interface Tunnel 0 //creating Virtual interface ip address 192.168.0.1 255.255.255.0 //Overlay/Private/admin define IP address exit ip route 0.0.0.0 0.0.0.0 172.16.1.1 //static routes pointing toward Internet simulated router
R2:
interface FastEthernet0/0
ip address 172.16.2.2 255.255.255.252
no shutdown
interface Tunnel 0
ip address 192.168.0.2 255.255.255.0
exit
ip route 0.0.0.0 0.0.0.0 172.16.2.1
interface loopback 1
ip address 22.22.22.22 255.255.255.0
exit
R3:
interface FastEthernet0/0
ip address 172.16.3.2 255.255.255.252
no shutdown
interface Tunnel 0
ip address 192.168.0.3 255.255.255.0
exit
ip route 0.0.0.0 0.0.0.0 172.16.3.1
interface loopback 1
ip address 33.33.33.33 255.255.255.0
exit
R4:
interface FastEthernet0/0
ip address 172.16.4.2 255.255.255.252
no shutdown
interface Tunnel 0
ip address 192.168.0.4 255.255.255.0
exit
ip route 0.0.0.0 0.0.0.0 172.16.4.1
interface loop 1
ip address 44.44.44.44 255.255.255.0
exit
Step 2: Configuring DMVP Process
R1: interface tunnel 0 //entering virtual interface tunnel 0 ip nhrp map multicast dynamic //enables forwarding of multicast traffic across the tunnel to dynamic spokes required by most routing protocols ip nhrp network-id 5 //uniquely identifies the DMVPN network; tunnels will not form between routers with differing network IDs tunnel source 172.16.1.2 //exit interface or NBMA address of exit interface tunnel mode gre multipoint //GRE mode multipoint ip mtu 1400 //tunning MTU because of DMVPN header exit
Here tunnel does not have an explicit destination specified because multipoint tunnels
are built dynamically from the spokes to the hub router; the huď router doesŶ’t Ŷeed to
be preconfigured with spoke addresses
R2: interface tunnel 0 //entering virtual interface tunnel 0 ip nhrp network-id 5 //nhrp network ID tunnel source 172.16.2.2 //exit interface or NBMA address of exit interface ip nhrp map 192.168.0.1 172.16.1.2 //statically maps the NHS address to R1’s physical address ip nhrp map multicast 172.16.1.2 //multicast traffic is only allowed from spokes to the hub, not from spoke to spoke ip nhrp nhs 192.168.0.1 // ip nhrp nhs 192.168.0.1 designates R1 as the Next Hop Server tunnel mode gre multipoint //GRE mode multipoint ip mtu 1400 //tunning MTU because of DMVPN header exit
R3:
int tunnel 0
ip nhrp network-id 5
tunnel source 172.16.3.2
ip nhrp map 192.168.0.1 172.16.1.2
ip nhrp map multicast 172.16.1.2
ip nhrp nhs 192.168.0.1
ip mtu 1400
tunnel mode gre multipoint
exit
R4:
int tunnel 0
ip nhrp network-id 5
tunnel source 172.16.4.2
ip nhrp map 192.168.0.1 172.16.1.2
ip mtu 1400
ip nhrp map multicast 172.16.1.2
ip nhrp nhs 192.168.0.1
tunnel mode gre multipoint
exit
Task 2: DMVPN Verification
Step 1: Verify DMVPN Tunnel creation
R1: R1#show dmvpn //shows detailts of dmvpn tunnel Legend: Attrb --> S - Static, D - Dynamic, I - Incomplete N - NATed, L - Local, X - No Socket # Ent --> Number of NHRP entries with same NBMA peer NHS Status: E --> Expecting Replies, R --> Responding UpDn Time --> Up or Down Time for a Tunnel
| Interface: Tunnel0, IPv4 NHRP Details | |||||
| Type:Hub, NHRP Peers:3, | |||||
| # Ent | Peer | NBMA Addr | Peer Tunnel Add State | UpDn Tm | Attrb |
| 1 | 172.16.2.2 | 192.168.0.2 | UP | 00:15:17 | D |
| 1 | 172.16.3.2 | 192.168.0.3 | UP | 00:00:05 | D |
| 1 | 172.16.4.2 | 192.168.0.4 | UP | 00:03:15 | D |
Hub and spoke setup would require three separate tunnels spanning from R1 to each of
the spoke routers
Hub router R1 has dynamically form the tunnel with every spoke using mGRE Multipoint
tunnel mode. Multipoint GRE tunnel allows for more than two endpoints, and is treated
as a non-broadcast multi-access (NBMA) network.
Conversely mGRE allows all four routers to have a single tunnel interface in the same IP
subnet (192.168.0.0/24).This NBMA configuration is enabled by Next Hop Resolution
Protocol, which allows multipoint tunnels to be built dynamically
R2: R2#show dmvpn //shows details of dmvpn tunnel Legend: Attrb --> S - Static, D - Dynamic, I - Incomplete N - NATed, L - Local, X - No Socket # Ent --> Number of NHRP entries with same NBMA peer NHS Status: E --> Expecting Replies, R --> Responding UpDn Time --> Up or Down Time for a Tunnel
| Interface: Tunnel0, IPv4 NHRP Details | |||||
| Type:Spoke, NHRP Peers:1 | |||||
| # Ent | Peer | NBMA Addr | Peer Tunnel Add State | UpDn Tm | Attrb |
| 1 | 172.16.1.2 | 192.168.0.1 | UP | 00:17:10 | S |
Initially every spoke router will form only static tunnel with only Hub router as multicast
traffic is only allowed from spokes to the hub, not from spoke to spoke.
R1#show ip nhrp //shows Next hop Resolution Protocol details 192.168.0.2/32 via 192.168.0.2 Tunnel0 created 00:21:37, expire 01:41:53 Type: dynamic, Flags: unique registered NBMA address: 172.16.2.2 192.168.0.3/32 via 192.168.0.3 Tunnel0 created 00:21:31, expire 01:42:21 Type: dynamic, Flags: unique registered NBMA address: 172.16.3.2 192.168.0.4/32 via 192.168.0.4 Tunnel0 created 00:21:32, expire 01:42:28 Type: dynamic, Flags: unique registered NBMA address: 172.16.4.2
R2#show ip nhrp //shows Next hop Resolution Protocol details 192.168.0.1/32 via 192.168.0.1 Tunnel0 created 00:13:01, never expire Type: static, Flags: NBMA address: 172.16.1.2
NHRP clients (spoke routers) issue requests to the next hop server (hub router) to obtain
the physical address of another spoke router.
NHRP facilitates dynamic tunnel establishment, providing tunnel-to-physical interface
address resolution
R2: R2#ping 192.168.0.4 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 192.168.0.4, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 348/539/832 ms
R4#traceroute 192.168.0.2
Type escape sequence to abort.
Tracing the route to 192.168.0.2
-
192.168.0.1 396 msec 508 msec 192.168.0.2 392 msec
Spoke router R4 is able to reach R2 via Hub router.
A packet destined from R4 to R2 would need to be routed through R1, to exit the R4
tunnel and the get re-encapsulated to enter the R2 tunnel