UltraZero,
For the Tunnel interface, I originally had the IP address for the tunnel source but changed it to the fastethernet interface so if/when the IP address changes, the tunnel will be using the correct IP address.

I've also used a Cisco 1751 router that has a WIC-1ADSL, eliminating the Speedstream modem, with the same results.

The speed of the DSL is 384k up/down.  Both routers can ping and traceroute to the IPv4 addresses, but timeout when trying IPv6.

Thanks for the security tips ... the config has been modified.

Mindlesstux,
I'm in Michigan.  The DSL service is AT&T's business service and they claim that they support IPv6 and nothing is being blocked.
Currently, I'm working on the C871W which is running 15.1.3T code.

I've configured a Cisco 871W router with the tunnel configuration from the create tunnel page.  The modem is passing the IP address to the WAN port on the router.  I've verified that the tunnel is up:
Tunnel0 is up, line protocol is up
  Hardware is Tunnel
  Description: Hurricane Electric IPv6 Tunnel Broker
  MTU 17920 bytes, BW 100 Kbit/sec, DLY 50000 usec,
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation TUNNEL, loopback not set
  Keepalive not set
  Tunnel source 99.54.133.206 (FastEthernet4), destination 209.51.181.2
   Tunnel Subblocks:
      src-track:
         Tunnel0 source tracking subblock associated with FastEthernet4
          Set of tunnels with source FastEthernet4, 1 member (includes iterators), on interface <OK>
  Tunnel protocol/transport IPv6/IP
  Tunnel TTL 255
  Tunnel transport MTU 1480 bytes
  Tunnel transmit bandwidth 8000 (kbps)
  Tunnel receive bandwidth 8000 (kbps)
  Last input 00:36:32, output 00:23:01, output hang never
  Last clearing of "show interface" counters never
  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 3
  Queueing strategy: fifo
  Output queue: 0/0 (size/max)
  5 minute input rate 0 bits/sec, 0 packets/sec
  5 minute output rate 0 bits/sec, 0 packets/sec
     6039 packets input, 724432 bytes, 0 no buffer
     Received 0 broadcasts (0 IP multicasts)
     0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
     6191 packets output, 499736 bytes, 0 underruns
     0 output errors, 0 collisions, 0 interface resets
     0 unknown protocol drops
     0 output buffer failures, 0 output buffers swapped out

When I try to ping the router side of the tunnel from the internet I can see the traffic crossing the tunnel and the router replying the the ping fails:

Mar 23 17:27:34: Tunnel0: IPv6/IP to classify 209.51.181.2->99.54.133.206 (tbl=0,"default" len=100 ttl=246 tos=0x0) ok, oce_rc=0x1
Mar 23 17:27:34: Tunnel0: IPv6/IP (PS) to decaps 209.51.181.2->99.54.133.206 (tbl=0, "default", len=100, ttl=246)
Mar 23 17:27:34: Tunnel0: decapsulated IPv6/IP packet (len 100)
Mar 23 17:27:34: ICMPv6: Received echo request, Src=2001:1AF8:4200:B000:20C:29FF:FE6B:49D2, Dst=2001:470:1F10:D9F::2
Mar 23 17:27:34: Tunnel0: IPv6/IP encapsulated 99.54.133.206->209.51.181.2 (linktype=79, len=100)
Mar 23 17:27:34: Tunnel0 count tx, adding 20 encap bytes
Mar 23 17:27:34: ICMPv6: Sent echo reply, Src=2001:470:1F10:D9F::2, Dst=2001:1AF8:4200:B000:20C:29FF:FE6B:49D2


It's as if the router doesn't know how to get back.  From the router I'm unable to ping the other side of the tunnel.

Here is the config that I'm using.  Maybe I'm over looking something.

version 15.1
no service pad
service timestamps debug datetime localtime
service timestamps log datetime localtime
service password-encryption
!
hostname lab-ipv6-gw01
!
boot-start-marker
boot system flash:c870-advipservicesk9-mz.151-3.T.bin
boot-end-marker
!
!
logging buffered 8192
!
no aaa new-model
!
memory-size iomem 20
clock timezone EST -5 0
clock summer-time EDT recurring
crypto pki token default removal timeout 0
!
!
dot11 syslog
ip source-route
!
!
!
!
!
ip cef
ipv6 unicast-routing
ipv6 cef
!
multilink bundle-name authenticated
!
!
!
!
!
!
!
!
!
!
!
!
interface Loopback0
 no ip address
 ipv6 address 2001:470:C2F2::1/48
 ipv6 enable
!
interface Tunnel0
 description Hurricane Electric IPv6 Tunnel Broker
 no ip address
 ipv6 address 2001:470:1F10:D9F::2/64
 ipv6 enable
 tunnel source FastEthernet4
 tunnel mode ipv6ip
 tunnel destination 209.51.181.2
!
interface FastEthernet0
!
interface FastEthernet1
!
interface FastEthernet2
!
interface FastEthernet3
!
interface FastEthernet4
 description WAN Link Interface
 ip address dhcp
 duplex auto
 speed auto
!
interface Dot11Radio0
 no ip address
 shutdown
 speed basic-1.0 basic-2.0 basic-5.5 6.0 9.0 basic-11.0 12.0 18.0 24.0 36.0 48.0 54.0
 station-role root
!
interface Vlan1
 ip address 192.168.200.49 255.255.255.0
 ipv6 address 2001:470:1F11:D9F::1/64
 ipv6 enable
!
ip forward-protocol nd
no ip http server
no ip http secure-server
!
!
ip route 10.0.0.0 255.0.0.0 192.168.200.254
ip route 172.16.0.0 255.240.0.0 192.168.200.254
ip route 192.168.0.0 255.255.0.0 192.168.200.254
!
logging esm config
ipv6 route ::/0 Tunnel0
!
!
!
!
!
control-plane
!
!
line con 0
 no modem enable
line aux 0
line vty 0 4
 session-timeout 15
 access-class 129 in
 exec-timeout 15 0
 privilege level 15
 logging synchronous
 login
 transport input telnet
!
scheduler max-task-time 5000

end

The router is running Advance IP Services 15.1.3T code.
I've also configured a 1751 with an ADSL WIC, running 12.3.6, and get the same results.
AT&T is the DSL provider and our account team swears they are not blocking any thing since it is a business DSL account.

Any ideas?