Or more specifically, NAT-PT.
This one is a really cool issue, took me a bit of troubleshooting but I finally tracked down my issue with NAT-PT. (NAT-PT is IPv4 to IPv6 Translation.)
As you can see with the output below, after configuring NAT-PT normally, only every other packet reaches it's destination.
R1#p 1.1.1.3 r 6
Type escape sequence to abort.
Sending 6, 100-byte ICMP Echos to 1.1.1.3, timeout is 2 seconds:
!.!.!.
Success rate is 50 percent (3/6), round-trip min/avg/max = 16/17/20 ms
Now, clearly this isn't what we'd like, we want all of our packets to reach our destination. The cause for this is what I must figure to be an IOS bug as the issue lies with CEF. By disabling IPv4 CEF (Only disabling IPv6 CEF had no effect, and I couldn't test if the issue was only IPv4 CEF as IPv6 CEF is reliant on IPv4) I was able to get all pings to be successful.
R1#p 1.1.1.3
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 1.1.1.3, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 16/18/20 ms
Here is the simple config I used, I edited out everything unnecessary. R1 is connected to R2 via ethernet while R2 connects to R3 via serial. (R1) ------ (R2) ---z--- (R3)
R1#show run
interface GigabitEthernet0/0
ip address 1.1.1.2 255.255.255.0
ip route 1.1.1.3 255.255.255.255 1.1.1.5
R2#show run
no ip cef
interface GigabitEthernet0/0
ip address 1.1.1.5 255.255.255.0
ipv6 nat
interface Serial0/0/1
ipv6 address 2001::5/96
ipv6 nat
ipv6 nat v4v6 source 1.1.1.2 2002::2
ipv6 nat v6v4 source 2001::3 1.1.1.3
ipv6 nat prefix 2002::2/96
R3#show run
interface Serial0/1/0
ipv6 address 2001::3/96
clock rate 128000
ipv6 route 2002::2/128 2001::5
Today's challenge is determining how to use the question mark character "?" in a password on a Cisco router when configuring a key-chain. Hrm. Puzzling.
(Key-chain is to be used with EIGRP Authentication, but that makes no difference.)
![Perfect World [PC]](http://www.spawnpoint.com/uploads/images/i1065.jpg)
