nd6_setmtu0: new link MTU on iwn0 (576) is too small for IPv6 which needs 1280

[Ottavio Caruso <ottavio2006-netbsd%yahoo.com@localhost>]

Hello,

uname -a:
NetBSD  6.1.5_PATCH NetBSD 6.1.5_PATCH (GENERIC) amd64

I have a problem with wireless connection and Netbsd that I don't have
with Windows 7 and Linux.

In the console I see:
nd6_setmtu0: new link MTU on iwn0 (576) is too small for IPv6 which
needs 1280
iwn0: discarding oversize frame (len=1484)

In "ifconfig iwn0" I have:

iwn0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 576
ssid TP-LINK_E6D338
powersave off
bssid 00:27:19:e6:d3:38 chan 6
address: 00:21:5c:55:ee:9d
media: IEEE802.11 autoselect (DS5 mode 11g)
status: active
inet 192.168.1.108 netmask 0xffffff00 broadcast 255.255.255.255
inet6 fe80::221:5cff:fe55:ee9d%iwn0 prefixlen 64 scopeid 0x2

Before connecting to the router the mtu was 1500 as it should be.

I can connect to the router but cannot browse any website.

I have manually changed the mtu on iwn0 to 1500 but I still have the
same problem.

I have removed all references to ip6 in rc.conf and rebooted the pc
but no avail.

I have played with the "ip6mode" value in rc.conf, setting it to
"autohost" also to no avail.

I have a good connection with the router and can ping any website, but
I can't traceroute or browse any website.

I have used Netbsd in the past with various routers and I've never had
any problem.

Any help willl be appreciated.