IPv6 Tunnels

Automatic 6to4 Tunnel

Tunnel format

2002(16 bits) + IPv4 address(32 bits) + Subnet(16 bits) + Interface ID(64 bits)

First 16 bits of 6to4 tunnel always starts with 2002.
Tunnel is point-to-multipoint in nature.
IPv4 address bits are written in HEX value here, for example, 1.1.1.1 = 0101:0101
When routed a packet through the tunnel, router looks at the IPv4 bits portion and forwards to the appropriate destination router.

R1 Config

interface Loopback0
 ip address 1.1.1.1 255.255.255.255
 ipv6 address 2002:101:101:1::1/64
!
interface Tunnel0
 ipv6 address 2002:101:101::1/64
 tunnel source Loopback0
 tunnel mode ipv6ip 6to4
!
interface FastEthernet0/0
 ip address 192.168.12.1 255.255.255.0
!
router ospf 1
 log-adjacency-changes
 network 1.1.1.1 0.0.0.0 area 0
 network 192.168.12.1 0.0.0.0 area 0
!
ipv6 route 2002::/16 Tunnel0

R2 Config

interface Loopback0
 ip address 2.2.2.2 255.255.255.255
!
interface FastEthernet0/0
 ip address 192.168.12.2 255.255.255.0
!
interface FastEthernet0/1
 ip address 192.168.23.2 255.255.255.0
!
router ospf 1
 log-adjacency-changes
 network 2.2.2.2 0.0.0.0 area 0
 network 192.168.12.2 0.0.0.0 area 0
 network 192.168.23.2 0.0.0.0 area 0

R3 Config

interface Loopback0
 ip address 3.3.3.3 255.255.255.255
 ipv6 address 2002:303:303:3::3/64
!
interface Tunnel0
 ipv6 address 2002:303:303::3/64
 tunnel source Loopback0
 tunnel mode ipv6ip 6to4
!
interface FastEthernet0/0
 ip address 192.168.23.3 255.255.255.0
!
router ospf 1
 log-adjacency-changes
 network 3.3.3.3 0.0.0.0 area 0
 network 192.168.23.3 0.0.0.0 area 0
!
ipv6 route 2002::/16 Tunnel0

Verification

R1#show ipv6 route

S   2002::/16 [1/0]
     via ::, Tunnel0
C   2002:101:101::/64 [0/0]
     via ::, Tunnel0
L   2002:101:101::1/128 [0/0]
     via ::, Tunnel0
C   2002:101:101:1::/64 [0/0]
     via ::, Loopback0
L   2002:101:101:1::1/128 [0/0]
     via ::, Loopback0
L   FE80::/10 [0/0]
     via ::, Null0
L   FF00::/8 [0/0]
     via ::, Null0

R1#ping 2002:0303:0303:3::3 source loopback 0
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 32/43/60 ms


-----------------------------------------------------------------------------------------------------

ISATAP Tunnel

Tunnel format

Prefix ID(64 bits) + 0000(16 bits) + 5EFE + IPv4 address(32 bits)

R1 Config

interface Loopback1
 ipv6 address 2001:1::1/64
!
interface Tunnel1
 no ip address
 no ip redirects
 ipv6 address 2001:13::/64 eui-64
 tunnel source Loopback0
 tunnel mode ipv6ip isatap
!
ipv6 route 2001:3::/64 2001:13::5EFE:303:303


R3 Config

interface Loopback1
 ipv6 address 2001:3::3/64
!
interface Tunnel1
 no ip address
 no ip redirects
 ipv6 address 2001:13::/64 eui-64
 tunnel source Loopback0
 tunnel mode ipv6ip isatap
!
ipv6 route 2001:1::/64 2001:13::5EFE:101:101

Verification


R1#show ipv6 interface brief | in Tunnel1

  Tunnel1                    [up/up]
    FE80::5EFE:101:101
    2001:13::5EFE:101:101


R3#show ipv6 interface brief | in Tunnel1

Tunnel1                    [up/up]
    FE80::5EFE:303:303
    2001:13::5EFE:303:303


R1#show ipv6 route | in 2001:3

S   2001:3::/64 [1/0]
     via 2001:13::5EFE:303:303

R1#ping 2001:3::3 source loopback 1
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 24/36/48 ms