Re: Terminal release ip command?

In article <58nr0kF2hcm5fU1@xxxxxxxxxxxxxxxxxx>, Ian Gregory
<foo@xxxxxxxxxxx> wrote:

I can get a whole /48 of IPv6 address space allocated to me at no extra
charge by my ADSL supplier (who only charge me UKP 20 + VAT per month
for the connection). But that would be excessively geeky even for me
so I stick with the single static IPv4 address (for which I have full
control of the forward and reverse DNS entries).

Very nice. I envy your IP connection.


I run without NAT, or firewall, everything works, and my configuration
is much easier. :-)

Apart from networking between the two machines right:-)

In a previous post you said that it is a problem when your two
DHCP addresses are on different netblocks so you need to keep
renewing a lease until they are on the same netblock.

So how are you routing between the two machines? Are you actually
sending packets out to your ISP's server room and waiting for
them to get back to you on the other line?

No. That is what happens if I am in different netblocks. The missing
key to your understanding is the Airport Extreme Base Station operating
in the bridged mode that I have not mentioned previously.

If I am in the same netblock the routing is *direct* via the routing
ability of my AEBS, not via the ISPs router.

That is OK at a pinch
but horribly laggy, low bandwidth, inefficient, insecure etc.
(analogus to two people sitting on a couch together and having
a conversation via cell phone instead of just talking directly).

Agreed.

The "standard" solution is to have a router make a connection and
pick up a single DHCP address from your ISP,

One nice thing about my ISP is they give two dynamic IP addresses to
the basic account hence I can network between my two Macs with the
constraints mentioned.

then network your
two machines to the router via Ethernet with either static or
DHCP IP addresses on your own private network and NAT taking care
of talking to the Internet. That way they can talk to each other
direct. The configuration is easy and it works.

I did run NAT. But I am always experimenting with new software.

And it seemed I would always be troubleshooting a problem down to my
NAT getting in the way. So I got fed up with NAT and I went bridged.

There is of course another possibility. Say for example you have
both machines independently connected to your ISP via dial-up
using their internal modems (you would need two phone lines).
Then you could *also* link the two machines directly via an Ethernet
cable (or perhaps even FireWire!), give them static IPs on any
bit of private IP space (eg 192.168.10.10 and 192.168.10.11)
and make sure they have sane routing tables (go via Ethernet
to get to 192.168.10.0 network, via modem to get anywhere else).
That way you would get fast networking between the machines which
works reliably regardless of whether your two ISP assigned
addresses are on the same netblock. This is not a common thing
to do but it should be relatively straightforward.

And just to return to the OP's original question, there is nothing
you can do to force your ISP's DHCP server to give you a new IP
address. It will give you whichever one it feels like and it will
normally be the same one you just had.

Yes you are right. Normal restarts, I always get the same IP address.
For months at a time.

But not if I issue a DHCP Release packet. In the last few minutes I
have had about 20 different IP addresses as I chased DHCP packets with
wireshark to see what was going on and as you may have read in another
post in this thread.

Cheers,

Darrell

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