IPv6 Tunneling - ISATAP

R2, R5 and R6 connected via an IPv4 frame-relay network.
There is no PVC in use between R5 and R6.
Each device has a loopback 192.168.x.x where x is router number.
The goal here is to allow the remote IPv6 networks to communicate over the IPv4 cloud.


Below are the configs.

Loopback 100 = tunnel endpoint
Loopback 101 = "remote" network

R6:

interface Loopback100
ip address 192.168.6.6 255.255.255.255

interface Loopback101
no ip address
ipv6 address 2001:600::6/64

interface Tunnel1
ipv6 address 2001:200::/64 eui-64
tunnel source Loopback100
tunnel mode ipv6ip isatap

R5:

interface Loopback100
ip address 192.168.5.5 255.255.255.255

interface Loopback101
no ip address
ipv6 address 2001:500::5/64

interface Tunnel1
ipv6 address 2001:200::/64 eui-64
tunnel source Loopback100
tunnel mode ipv6ip isatap

Static routes on R5 and R6:

R5(config)#ipv6 route 2001:600::/64 tunnel 1 fe80::5efe:c0a8:0606

R6(config)#ipv6 route 2001:500::/64 tunnel 1 fe80::5efe:c0a8:0505

Where did I get these next hops? Well when you create an ISATAP tunnel they are created in a modified eui-64 format. Take a look

at R5:

R5#show ipv6 interface brief tun 1
Tunnel1 [up/up]
FE80::5EFE:C0A8:505
2001:200::5EFE:C0A8:505

When the router decides to route a packet out of that tunnel interface, it calculates the Ipv4 next hop address from the last 32 bits of the modified eui-64 address. In this case C0A8:505 converts to 192.168.5.5. R6 sends all packets destined for 2001:500::/64 to 192.168.5.5.

Key things to remember:

-The tunnel source address must be reachable by remote routers
-There is no manually specified tunnel destination
-You must specify the tunnel interface and link layer address in static routes

IPv6 tunneling - gre ip

This example is going to use the same topology as IPv6 tunneling - IPv6IP. In this mode, the passenger protocol is IPv6, the carrier protocol is GRE and IPv4 is used as the transport.

Here is the network:

[R1]---[R2]---[R3]---[R4]

R1-R2: IPv6 network 2002:1:0:12::/64
R2-R3: IPv4 network 172.12.23.0/24
R3-R4: IPv6 network 2002:1:0:34::/64

Make sure you enable ipv6 unicast routing on R2 and R3:

R2(config)#ipv6 unicast-routing

R3(config)#ipv6 unicast-routing

Configuration is pretty much the same as ipv6ip except the mode is different. In fact, we don't even need to specify a mode as gre ip is the default. I will show it here just for clarity but note that it will probably not show up in the running-config:

R2(config)#int tunnel 1
R2(config-if)#description gre ip tunnel
R2(config-if)#ipv6 address 2002:2:0:23::2/64
R2(config-if)#tunnel source 172.12.23.2
R2(config-if)#tunnel destination 172.12.23.3
R2(config-if)#tunnel mode gre ip

R3(config)#int tunnel 1
R3(config-if)#description gre ip tunnel
R3(config-if)#ipv6 address 2002:2:0:23::3/64
R3(config-if)#tunnel source 172.12.23.3
R3(config-if)#tunnel destination 172.12.23.2
R3(config-if)#tunnel mode gre ip

Let's add the static routes:

R2(config)#ipv6 route 2002:1:0:34::/64 Tunnel1

R3(config)#ipv6 route 2002:1:0:12::/64 Tunnel1

Verify:

R1#ping 2002:1:0:34::4

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 2002:1:0:34::4, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 44/70/88 ms

R2#debug tunnel
Tunnel Interface debugging is on
R2#
*Mar 1 01:09:12.999: Tunnel1: GRE/IP encapsulated 172.12.23.2->172.12.23.3 (linktype=79, len=124)
*Mar 1 01:09:13.095: Tunnel1: GRE/IP to classify 172.12.23.3->172.12.23.2 (len=124 type=0x86DD ttl=254 tos=0x0)

Some of the benefits of this mode are that GRE tunnels can carry more than just IPv6. At work, we sometimes use them for multicast and some other non-IP traffic, we even use them to route normal IP packets to default destinations across VPN clouds.

IPv6 tunneling - IPv6IP

This is a pretty simple and straightforward manual method of tunneling IPv6 packets over an IPv4 network. IP protocol type 41 is used to tell the router that the packet inside of the IP packet is and IPv6 packet.

Here is the network:

[R1]---[R2]---[R3]---[R4]

R1-R2: IPv6 network 2002:1:0:12::/64
R2-R3: IPv4 network 172.12.23.0/24
R3-R4: IPv6 network 2002:1:0:34::/64

Make sure you enable ipv6 unicast routing on R2 and R3:

R2(config)#ipv6 unicast-routing

R3(config)#ipv6 unicast-routing

Let's create the tunnels:

R2(config)#int tunnel 0
R2(config-if)#ipv6 address 2002:1:0:23::2/64
R2(config-if)#tunnel source 172.12.23.2
R2(config-if)#tunnel destination 172.12.23.3
R2(config-if)#tunnel mode ipv6ip

R3(config)#int tun 0
R3(config-if)#ipv6 address 2002:1:0:23::3/64
R3(config-if)#tunnel source 172.12.23.3
R3(config-if)#tunnel destination 172.12.23.2
R3(config-if)#tunnel mode ipv6ip

Next we need tell the router when to use the tunnel by making some static routes. The following route tells R2 that whenever a packet comes in destined for the R3-R4 network, encapsulate it in IP and tunnel it to the tunnel destination, R3 in this case. The second route does the opposite on R3.

R2(config)#ipv6 route 2002:1:0:34::/64 tunnel 0

R3(config)#ipv6 route 2002:1:0:12::/64 tunnel 0

Let's verify:

R1#ping 2002:1:0:34::4

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 2002:1:0:34::4, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 56/76/124 ms