[c-nsp] IOS IPv6 CEF adjacencies on 12xxx

[bill fumerola]

N.B. it's been a half-decade since i've touched a cisco 12k.

On Tue, Dec 09, 2008 at 06:15:49PM -0000, David Freedman wrote:
> ra#sh ipv6 int tun0
> Tunnel0 is up, line protocol is up
>   IPv6 is enabled, link-local address is FE80::C316:9EE 
> rb#sh ipv6 int tun0
> Tunnel0 is up, line protocol is up
>   IPv6 is enabled, link-local address is FE80::C316:9ED 
> 
> Also, from the perspective of CEF, all seems to be ok on the surface:
> 
> ra#sh ipv6 cef tun0                     
> 2001:DB8:B::/48
>      nexthop FE80::C316:9ED Tunnel0 
               ^^^^^^^^^^^^^^
> 2001:DB8:1::/126
>      attached to Tunnel0 
> 
> rb#sh ipv6 cef tun0                     
> 2001:DB8:A::/48
>      nexthop FE80::C316:9ED Tunnel0 
               ^^^^^^^^^^^^^^
     should be FE80::C316:9EE if this was a paste-o, ignore this mail
> 2001:DB8:1::/126
>      attached to Tunnel0 

> ra#sh ipv6 cef exact-route 2001:db8:a::1 2001:db8:b::1
>  2001:DB8:A::1     -> 2001:DB8:B::1 interface Tunnel0
> 
> rb#sh ipv6 cef exact-route 2001:db8:b::1 2001:db8:a::1
>  2001:DB8:B::1     -> 2001:DB8:A::1 interface Tunnel0
> 
> **BUT**
> 
> if you dig deeper, you find that this isn't the case at all:
> 
> ra#execute-on slot <LANCARD> sh ipv6 cef exact-route 2001:db8:a::1 2001:db8:b::1
>  2001:DB8:A::1     -> 2001:DB8:B::1 interface Tunnel0
>  Adjacency is incomplete so not cef switched
> 
> ra#execute-on slot <WANCARD> sh ipv6 cef exact-route 2001:db8:a::1 2001:db8:b::1
>  2001:DB8:A::1     -> 2001:DB8:B::1 interface Tunnel0
>  Adjacency is incomplete so not cef switched
> 
> but this message does not appear on rb

guess:
since rb doesn't point to FE80::C316:9EE there's no adjacency to be
incomplete.

does 'sh ipv6 cef unresolved' show anything?

i'm hitting the limits of my knowledge.

> So, it looks like the lack of adjacency is the cause, 
> before I go open a TAC case (and get told to clear dCEF tables/
> reboot linecards) , is there anything non-invasive I could try to debug/resolve this?

how are RA,RB getting routes for 2001:DB8:A::1 and 2001:DB8:B::1?
if dynamically, try static. if static, try a routing protocol. just to
mix things up. :)

a pair of cisco 7301s, albeit running GRE and not ip6ip (sorry)

rtr1.n>show ipv6 int tun1003 | i link
  IPv6 is enabled, link-local address is FE80::217:FFF:FE1C:BC1B
rtr1.n>show ipv6 cef tun1003
AAAA:0:BBF:1::1/128
  nexthop FE80::217:FFF:FE07:2C1B Tunnel1003
[... other learned networks with the same output ...]
rtr1.n>show ipv6 int lo0 | i subnet
    AAAA:0:BBC:1::1, subnet is AAAA:0:BBC:1::1/128
rtr1.n>show ipv6 cef exact-route AAAA:0:BBC:1::1 AAAA:0:BBF:1::1
AAAA:0:BBC:1::1 -> AAAA:0:BBF:1::1 => IPV6 adj out of Tunnel1003
rtr1.n>

rtr1.p>show ipv6 int tun1003 | i link
  IPv6 is enabled, link-local address is FE80::217:FFF:FE07:2C1B
rtr1.p>show ipv6 cef tun1003
AAAA:0:BBC:1::1/128
  nexthop FE80::217:FFF:FE1C:BC1B Tunnel1003
[... other learned networks with the same output ...]
rtr1.p>show ipv6 int lo0 | i subnet
    AAAA:0:BBF:1::1, subnet is AAAA:0:BBF:1::1/128
rtr1.p>
rtr1.p>show ipv6 cef exact-route AAAA:0:BBF:1::1 AAAA:0:BBC:1::1
AAAA:0:BBF:1::1 -> AAAA:0:BBC:1::1 => IPV6 adj out of Tunnel1003
rtr1.p>

unless your output from above is a paste-o, it looks like the link-local
addresses aren't being resolved properly between RA and RB at your end.
in my scenario, the output of 'sh ipv6 cef' corresponds to the link-local
address of the tunnel at the far side.

however, i both don't have "attached to TunnelX" and the resolution
through that in my cef tables because i use unnumbered ipv6 interfaces
and run ospf3 across them. 

 ipv6 address autoconfig
 ipv6 unnumbered Loopback0

maybe instead of the /126 you could try using unnumbered loopbackX.

-- bill

p.s. 12.2(31)SB11, if it matters