[Techtalk] Cisco routers anyone?

Maria Blackmore mariab at cats.meow.at
Fri May 9 02:56:11 EST 2003

On Fri, 9 May 2003, James Sutherland wrote:

> From: "Mary Wood" <empea at yahoo.com>
> > I'm in global config mode, trying the entry:
> >
> > router(config)#ip address 12.345.678.9
> >
> > 12.345... being the new ip we want and 255... being
> > the subnet.
> Is that the actual IP, or did you mask it for email purposes? If the former,
> 12.345.678.9 is an invalid IP address: each of the four octets must be
> between 0 and 255 inclusive.

presumably this is an example, but Cisco's are smart, and will be very
polite about telling you that you've done something very stupid


router(config-if)#ip address 12.345.678.9
% Invalid input detected at '^' marker.

As you can see, it's pointing at the 5, which is where it's detected
things have gone wonky :)

> If you're wanting some private IP address for your internal network, use one
> of the spaces reserved by RFC1918:, and
> That way, you're guaranteed never to conflict with genuine
> public Internet addresses; the address you were attempting to use would be
> in the AT&T Bell Labs address range, allocated June 1995.

It is, however, rather unlikely that Bell Labs will actually be using that
much of this *enormous* address range that they were allocated, but I'm
just cynical like that.

Actually, I have the means to ... co-opt some of AT&T's IP addresses
... at least for as long as it takes for the phones to start ringing with
"upset" people on the other end.


> Personally, I use for my router/firewall, and have machines at
> upwards via DHCP.

Cisco's are also DHCP savvy, if you're interesting.

Wonderful little boxes, it's a shame that many of them are rather
expensive, or more specifically, out of the price range of the normal

Oh, and I forgot from my previous email, if an interface doesn't appear to
be doing anything, check to see if it's showing as "Administratively
down", to change this use the "no shutdown" command when configuring an
interface.  Oh and label the interfaces, so you know what they are with
the "description" command.


Network Fairy

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