Target Networking

In this topology IPv6 tunnel is made over IPv4 network, color dark red representing the IPv4 network whereas color blue is showing IPv6 Network with IPv6 tunnel. EIGRP routing protocol is used for communication between both network IPv4 as well as IPv6. IPv4 network is using EIGRP 1 and IPv6 network is using EIGRP 2.

This topology is a example of Manually Configured Tunnel (MCT) which is a type of Static Point-to-Point IPv6 Tunnel. This lab is based on Manually Configured tunnel in which Tunnel mode is ipv6ip. RFC 4213 is made for this MCT tunnel.
There are two types of Static Point-to-Point tunnel :-
1. Manually Configured Tunnels (MCT)
2. Generic Routing Encapsulation (GRE) tunnels

In order to support the IGP`s and other features in these static tunnels router will assign link local addresses on these links and allow the forwarding of IPv6 multicast traffic.

This topology is clearing the concept that, if Router has only IPv6 addresses over it and no IPv4 addresses then we have to give Router-ID in the routing protocol otherwise that router will not communicate with the other routers because it will not have any route to other routers.
So here Router R5 and R6 has the Router-ID 5.5.5.5 and 6.6.6.6 .
Tunneling is one of the way to communicate IPv6 with IPv4 network. In this topology IPv6 tunnel is made from Router R1 to R4, and this tunnel has the IP address from subnet 2003::/64.

In GNS3, IPv6 routing have to be enabled on interface, it can not enabled by the network command in routing protocol.

IPv6 Tunnel

On Router R1- interface Tunnel0

no ip address
ip mtu 1000
ipv6 address 2003::1/64
ipv6 eigrp 2
tunnel source FastEthernet0/0
tunnel destination 10.3.0.2
tunnel mode ipv6ip


On Router R4-
interface Tunnel0

no ip address
ip mtu 1000
ipv6 address 2003::2/64
ipv6 eigrp 2
tunnel source FastEthernet0/0
tunnel destination 10.1.0.1
tunnel mode ipv6ip

GRE Tunnel

Ping from Router R5 to R6
R5#ping 2002::1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 2002::1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 72/106/212 ms
  
Ping from Router R6 to R5
R6#ping 2001::1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 2001::1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 68/78/88 ms

Traceroute from R5 to R6

R5#traceroute 2002::1
Type escape sequence to abort.
Tracing the route to 2002::1

  1 2001::2 56 msec 8 msec *
  2 2003::2 80 msec 72 msec 56 msec
  3 2002::1 104 msec 76 msec 44 msec

Configuration File config.zip

If you are interested in procuring the .net file for GNS3 then enter your email id in comment box.

I searched everywhere on internet about this error. I faced this error yesterday, on internet i found that this error is due to MTU packet size. It is quite surprising for me that MTU is creating problem, because I have learned that router perform fragmentation, segmentation if packet is large. But I found that these processes does not occur in this case. Because all EIGRP packets are trasported as IP protocol type 88 using Reliable Transport Protocol (RTP), not TCP or UDP, while Fragmentation is the mechanism in TCP transport.

EIGRP has a problem of flapping (up/down) in some topologies. It makes the network unstable, which creates problem in communication. This problem shows errors like this :-
 
%DUAL-5-NBRCHANGE: IPv6-EIGRP(0) 1: Neighbor FE80::2 (Tunnel0) is up: new adjacency

%DUAL-5-NBRCHANGE: IPv6-EIGRP(0) 1: Neighbor FE80::2 (Tunnel0) is down: holding time expired