[c-nsp] IOS 15.0 ipv6-related weirdness (fails to fallback to ipv4)

[Matthew Huff]

> Is "ipv6 enable" configured on any interface at all?  What does a "show
> ipv6 interfaces" say?
> 
> With ipv6-unicast routing disabled, the router will still function as
> an
> ipv6 host if there are any IPv6 configured interfaces.  And google
> returns both an A and AAAA record for google.com.

This was my first thought also, however, the post of:

c2800#sh ipv6 interface brief
 FastEthernet0/0            [up/up]
     unassigned
 FastEthernet0/1            [up/up]
     Unassigned

Appears to disprove that. I would think this is just a bug.


----
Matthew Huff             | 1 Manhattanville Rd
Director of Operations   | Purchase, NY 10577
OTA Management LLC       | Phone: 914-460-4039
aim: matthewbhuff        | Fax:   914-460-4139

> -----Original Message-----
> From: cisco-nsp-bounces at puck.nether.net [mailto:cisco-nsp-
> bounces at puck.nether.net] On Behalf Of Bruce Pinsky
> Sent: Monday, July 09, 2012 9:39 PM
> To: Michael Ulitskiy
> Cc: cisco-nsp at puck.nether.net
> Subject: Re: [c-nsp] IOS 15.0 ipv6-related weirdness (fails to fallback
> to ipv4)
> 
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
> 
> Michael Ulitskiy wrote:
> > Hello,
> >
> > I have a 2800 router with IOS 15.0(1)M7 with no ipv6 connectivity.
> > There are no ipv6 addresses configured on any interfaces and i've
> added:
> >
> > no ipv6 cef
> > no ipv6 unicast-routing
> >
> > commands to config.
> >
> > Nonetheless when I try to ping google the following happens:
> >
> > c2800#ping google.com
> > Translating "google.com"...domain server (167.206.112.138) [OK]
> >
> > Type escape sequence to abort.
> > Sending 5, 100-byte ICMP Echos to 2607:F8B0:4006:801::1004, timeout
> is 2 seconds:
> >
> > % No valid source address for destination Success rate is 0 percent
> > (0/1)
> >
> > c2800#sh hosts
> > Default domain is aceinnovative.com
> > Name/address lookup uses domain service Name servers are
> > 167.206.112.138, 167.206.7.4
> >
> > Codes: UN - unknown, EX - expired, OK - OK, ?? - revalidate
> >        temp - temporary, perm - permanent
> >        NA - Not Applicable None - Not defined
> >
> > Host                      Port  Flags      Age Type   Address(es)
> > google.com                None  (temp, OK)  0  IPv6
> 2607:F8B0:4006:801::1004
> >
> > So when it sees AAAA record it tries to use it (regardless ipv6
> > routing has been disabled), sees there're no valid ipv6 addresses to
> > use as source and fails, instead of trying to use alternative
> > ipv4 addresses. It's also very strange that only IPv6 address has
> been cached by resolver.
> > It looks like resolver discards any A record in the presence of AAAA.
> >
> > FYI:
> > c2800#sh ipv6 interface brief
> > FastEthernet0/0            [up/up]
> >     unassigned
> > FastEthernet0/1            [up/up]
> >     unassigned
> >
> > c2800#sh ipv6 route
> > IPv6 Routing Table - default - 1 entries
> > Codes: C - Connected, L - Local, S - Static, U - Per-user Static
> route
> >        B - BGP, HA - Home Agent, MR - Mobile Router, R - RIP
> >        I1 - ISIS L1, I2 - ISIS L2, IA - ISIS interarea, IS - ISIS
> summary
> >        D - EIGRP, EX - EIGRP external, ND - Neighbor Discovery
> >        O - OSPF Intra, OI - OSPF Inter, OE1 - OSPF ext 1, OE2 - OSPF
> ext 2
> >        ON1 - OSPF NSSA ext 1, ON2 - OSPF NSSA ext 2
> > L   FF00::/8 [0/0]
> >      via Null0, receive
> >
> > I wonder if this is a known issue, if there are any workarounds or if
> I'm missing something?
> 
> 
> - --
> =========
> bep
> 
> 
> 
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