ipv6 crashes cable modem

[Kyle Bolton]

Ive had this happen on 2 totally different modems (make and model) now so pretty sure its a bug or something with the router. I so much as enable ipv6 on the interface, dont even turn on dhcpv6 or anything, and the modem (cable) its attached to crashes. Other interface connected to a switch, no issues downstream.

c2800nm-adventerprisek9-mz.151-4.M10

relivant show run:

ipv6 unicast-routing

ipv6 cef

interface FastEthernet0/0
 ip address dhcp
 ip access-group 102 in
 no ip redirects
 no ip unreachables
 no ip proxy-arp
 ip nat outside
 ip inspect fwout out
 ip virtual-reassembly in

 ipv6 enable
 load-interval 30
 duplex auto
 speed auto
 no cdp enable
 no mop enabled

[marhill2]

Same issue here as well. What really weird is I disabled IPv6 with the no IPv6 enable command. Once I did this the modem gives me both a IPv4 address and an IPv6 address. As soon as I enable IPv6 unicast-routing though I lose internet connection and can not browse over v6 or v4. This is on a Cisco 2821 box with code c2800nm-adventerprisek9-mz.151-4.M12a.bin