Introduction
This document provides sample configuration of IPv6 6to4 tunneling in Cisco IOS routers. 6to4 Tunneling is one of the IPv6 translation mechanism which encapsulates the IPv6 packets into IPv4 which allows remote IPv6 networks to communicate across the IPv4 infrastructure(core network or Internet). The main difference between the manual tunnels and automatic 6to4 tunnels is that the tunnel is not point-to-point but it is point-to-multipoint.
In automatic 6to4 tunnels, the IPv4 infrastructure is treated as a virtual nonbroadcast multiaccess (NBMA) link routers are not configured as point-to-point. The IPv4 address embedded in the IPv6 address is used to find the other end of the automatic tunnel.
Requirements
Refer to Implementing IPv6 Addressing and Basic Connectivity for basic understanding on IPv6.
Background
In this example, router R1 and R2 are connected via Gigabit Ethernet G1/0. The routers R1 and R2 runs OSPFv3 in their internal network with routers R3 and R4 respectively. Note that internal routing protocols such as EIGRPv6 OSPFv3 cannot be used across the 6to4 tunnels since they use Link-Local address to form adjacencies. You can either use BGP which forms adjacencies using Global Unicast Address or Static routes as we use in this example.
Note: All configuration is tested on Cisco 7200 Series Router running on IOS Version 15.0(1)M Advance IP Services Image.
Topology Diagram
Configuration
Router R1
Router R2
Router R3 & R4
! ipv6 route 2002:C0A8:1E02::/48 Tunnel0 ipv6 route 1010::/64 2002:C0A8:1E02:: ! ipv6 router ospf 1
| ! ipv6 route 2002:C0A8:1E01::/48 Tunnel0 ipv6 route 1000::/64 2002:C0A8:1E01:: ipv6 router ospf 1
| ! version 15.2 ! hostname R3 ! ipv6 unicast-routing
ipv6 cef
! |
Note: Necessary Static routes are configured to achieve connectivity across 6to4 tunnel. First a static route is created for 2002:C0A8:1E02::/48 to be reachable via Tunnel Interface and then another static route for the internal /64 route which is to be routed via 6to4 tunnel interface.
Verify Commands
Ping
To verify the connectivity across the 6to4 tunnels, you can ping the internal networks of router R1 and R2. i.e. The routers R4 and R3 should be able to ping each other.
In router R3
Try ping router R4 (1010::2) from router R3
.
R3#ping 1010::2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 1010::2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 88/156/240 ms
Similarly from Router R4, ping router R3 (1000::1)
R4#ping 1000::1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 1000::1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 64/212/548 ms
Show ipv6 route
To display routing table information
R1#show ipv6 route
IPv6 Routing Table - default - 7 entries
Codes: C - Connected, L - Local, S - Static, U - Per-user Static route
B - BGP, HA - Home Agent, MR - Mobile Router, R - RIP
I1 - ISIS L1, I2 - ISIS L2, IA - ISIS interarea, IS - ISIS summary
D - EIGRP, EX - EIGRP external, ND - Neighbor Discovery
O - OSPF Intra, OI - OSPF Inter, OE1 - OSPF ext 1, OE2 - OSPF ext 2
ON1 - OSPF NSSA ext 1, ON2 - OSPF NSSA ext 2
O 1000::1/128 [110/1]
via FE80::C807:8EFF:FEB4:1C, FastEthernet2/0
LC 1000::2/128 [0/0]
via FastEthernet2/0, receive
S 1010::/64 [1/0]
via 2002:C0A8:1E02::
C 2002:C0A8:1E01::/48 [0/0]
via Tunnel0, directly connected
L 2002:C0A8:1E01::/128 [0/0]
via Tunnel0, receive
S 2002:C0A8:1E02::/48 [1/0]
via Tunnel0, directly connected
L FF00::/8 [0/0]
via Null0, receive
R2#show ipv6 route
IPv6 Routing Table - default - 7 entries
Codes: C - Connected, L - Local, S - Static, U - Per-user Static route
B - BGP, HA - Home Agent, MR - Mobile Router, R - RIP
I1 - ISIS L1, I2 - ISIS L2, IA - ISIS interarea, IS - ISIS summary
D - EIGRP, EX - EIGRP external, ND - Neighbor Discovery
O - OSPF Intra, OI - OSPF Inter, OE1 - OSPF ext 1, OE2 - OSPF ext 2
ON1 - OSPF NSSA ext 1, ON2 - OSPF NSSA ext 2
S 1000::/64 [1/0]
via 2002:C0A8:1E01::
O 1010::1/128 [110/1]
via FE80::C808:8EFF:FEB4:1C, FastEthernet2/0
LC 1010::2/128 [0/0]
via FastEthernet2/0, receive
S 2002:C0A8:1E01::/48 [1/0]
via Tunnel0, directly connected
C 2002:C0A8:1E02::/48 [0/0]
via Tunnel0, directly connected
L 2002:C0A8:1E02::/128 [0/0]
via Tunnel0, receive
L FF00::/8 [0/0]
via Null0, receive
You can see that the static routes are shown in the routing table and is received via Tunnel 0.
Show ipv6 interface tunnel 0
To display the detailed information of the interface, use this command
R1#show ipv6 interface tunnel 0
Tunnel0 is up, line protocol is up
IPv6 is enabled, link-local address is FE80::C0A8:1E01
No Virtual link-local address(es):
Global unicast address(es):
2002:C0A8:1E01::, subnet is 2002:C0A8:1E01::/48
Joined group address(es):
FF02::1
FF02::2
FF02::1:FF00:0
FF02::1:FFA8:1E01
MTU is 1480 bytes
ICMP error messages limited to one every 100 milliseconds
ICMP redirects are enabled
ICMP unreachables are sent
ND DAD is not supported
ND reachable time is 30000 milliseconds (using 30000)
Hosts use stateless autoconfig for addresses.
Traceroute
To trace the path of the packet for reaching the destination use this command.
R3#traceroute 1010::2
Type escape sequence to abort.
Tracing the route to 1010::2
1 1000::2 144 msec 156 msec 28 msec
2 2002:C0A8:1E02:: 184 msec 112 msec 120 msec
You can see that the router R3 reaches the network 1010:: via Tunnel interface
References
- Implementing Tunneling for IPv6
- IPv6:Providing IPv6 Services over an IPv4 Backbone Using Tunnels
- IPv6 Tunnel through an IPv4 Network
- IP Version 6 (IPv6) - Cisco Systems
- Cisco IOS IPv6 Command Reference
- IPv6 - Frequently Asked Questions
Routing Information Protocol