ifconfig lo1 down

[Julian Elischer]

On 3/5/11 10:43 AM, fredrik danerklint wrote:
> Hi,
>
> I would like to know what is the differents between ip4 and ip6 for this
> command.
>
> First:
>
> #ifconfig lo1
> lo1: flags=8049<UP,LOOPBACK,RUNNING,MULTICAST>  metric 0 mtu 16384
>          options=3<RXCSUM,TXCSUM>
>          inet xx.xx.xx.2 netmask 0xffffffff
>          inet6 2a03:xxxx:xxxx::xxxx:xx02 prefixlen 128
>          nd6 options=3<PERFORMNUD,ACCEPT_RTADV>
>
> $ ping xx.xx.xx.2
> PING xx.xx.xx.2 (xx.xx.xx.2): 56 data bytes
> 64 bytes from xx.xx.xx.2: icmp_seq=0 ttl=64 time=0.012 ms
> 64 bytes from xx.xx.xx.2: icmp_seq=1 ttl=64 time=0.010 ms
> ^C
>
> and
>
> $ ping6 2a03:xxxx:xxxx::xxxx:xx02
> PING6(56=40+8+8 bytes) 2a03:xxxx:xxxx::xxxx:xx02 -->  2a03:xxxx:xxxx::xxxx:xx02
> 16 bytes from 2a03:xxxx:xxxx::xxxx:xx02, icmp_seq=0 hlim=64 time=0.053 ms
> 16 bytes from 2a03:xxxx:xxxx::xxxx:xx02, icmp_seq=1 hlim=64 time=0.032 ms
> ^C
>
> Now we run this command:
>
> # ifconfig lo1 down
>
> and trying to ping again:
>
> $ ping xx.xx.xx.2
> PING xx.xx.xx.2 (xx.xx.xx.2): 56 data bytes
> ping: sendto: No route to host
> ping: sendto: No route to host
> ping: sendto: No route to host
> ^C
> --- xx.xx.xx.2 ping statistics ---
> 3 packets transmitted, 0 packets received, 100.0% packet loss
>
> works as expected (and this is what I want) but this command, however:
>
> $ ping6 2a03:xxxx:xxxx::xxxx:xx02
> PING6(56=40+8+8 bytes) 2a03:xxxx:xxxx::xxxx:xx02 -->  2a03:xxxx:xxxx::xxxx:xx02
> 16 bytes from 2a03:xxxx:xxxx::xxxx:xx02, icmp_seq=0 hlim=64 time=0.048 ms
> 16 bytes from 2a03:xxxx:xxxx::xxxx:xx02, icmp_seq=1 hlim=64 time=0.033 ms
> 16 bytes from 2a03:xxxx:xxxx::xxxx:xx02, icmp_seq=2 hlim=64 time=0.032 ms
> ^C
> --- 2a03:xxxx:xxxx::xxxx:xx02 ping6 statistics ---
> 3 packets transmitted, 3 packets received, 0.0% packet loss
> round-trip min/avg/max/std-dev = 0.032/0.038/0.048/0.007 ms
>
> My question is why is it not the same behavior of ip6 as of ip4?

I think IPV6 realizes it's sending to itself and short circuits it..

also, show ipv6 routes