From: Michael Snyder (msnyder@revolutioncomputer.com)
Date: Sun Dec 07 2003 - 17:31:30 GMT-3
After reading the related CCO material and Howard's posting. Some
questions come to mind.
Steps
1) I take it that once the new router dhcp's an address from a lan
interface or indirectly slarp's address info from the hdlc interface.
2) Then it tries to resolve it's hosts name via various methods, thought
rarp seems the easiest.
3) Then it tftp's (from address 255.255.255.255) it's named config file.
Question, what does the router do with this ip addressing info if the
autoinstall fails?
After reading the postings, one could assume that new routers would
always pull in an dhcp address from a lan interface or indirectly a
slarp address on a serial line.
Yet I've never saw a new router pull in an address from an existing
network without me telling it to do so.
What about frame relay with multiple dlci ? In a flash of insight,
maybe the frame-relay mappings to 0.0.0.0 are part of the autoinstall
process.
I'm guessing that the frame-relay autoinstall process is pure dhcp, with
address 0.0.0.0 broadcasting to 255.255.255.255 for an ip address, then
a (reverse/inverse?) arp for the name, then after that tftp get to
255.255.255.255 on all dlci for the named config file, with the ip
helper redirects to the tftp server.
Do have this roughly right?
How would you practice this in a remote lab, without a pc based
dhcp/tftp server?
I think I could config a router, copy the finished config to a 3550
filesystem, then configure the 3550 for all the needed dhcp/tftp/rarp
services, then erase the router, and autoinstall off the 3550.
Also could frame-relay ip helper to the 3550 also.
I heard that frame-relay has to support inverse-arp on the donor router.
Can someone clarify this? Yet if the main router is running frame-relay
maps, inverse-arp shouldn't work. Maybe they meant reverse arp.
Also read that slarp has to have a address of .1 or .2
Any other issues come to mind?
Thanks for Your Time in Advance.
Michael
-----Original Message-----
From: Howard C. Berkowitz [mailto:hcb@gettcomm.com]
Sent: Friday, December 05, 2003 6:02 PM
To: ccielab@groupstudy.com
Subject: Re: The dumbest question ever.
At 9:47 PM +0000 12/5/03, Ken.Farrington@barclayscapital.com wrote:
>How the hell does autoinstall work :) been looking at the docs and its
all
>cricket to me?
The daddy router has the seed and plants it in the mommy router...
No, that's probably not it. Autoinstall, more likely, was designed
by someone on Really Good Drugs. Let us tell the Christmas Story of
Autoinstall, and how the DNS and TFTP Servers at the North Pole
autoinstall configurations in Nice, not Naughty, routers.
When you get to the First Level of Understanding of Autoinstall, you
will think it's a magnificent joke. Anything that uses something
called SLARP must be a Monty Python routine. True Enlightenment
comes when you realize it is NOT a joke.
Reindeer probably get involved somewhere. (there's a URL at the end
if you don't like stories). This is a generic description; you'll
want to look at the URL for specific variations for specific
interface types.
Begin on Christmas morning, when the new router awakens.
1. I am a newly awakened router. I know nothing...I think.
2. Instinctively, I know that I can request an IP address on some
interface,
in some interface-dependent way like SLARP or DHCP.
I get an IP address. If I don't, I die.
3. Now I know my IP address. First, I send out a TFTP request for a file
called cisconet.cfg. This is the First Magic File Name to ask for.
If I get it, it will contain ip host statements from which I can map
my IP address to a hostname. If I can map that way, I go to step 8.
4. If I don't get the First Magic File, I broadcast a reverse DNS lookup
and see if there's a nice DNS server that will tell me my name. If
I learn my True Name, I go to step 8.
5. If DNS thinks I'm naughty and won't talk to me, I try to TFTP again,
this time looking for the Second Magic File, network-confg. If I
get the
Second Magic File, I learn my True Name from its IP host statements
and
go to step 8.
6. If there is no Second Magic File Fairy, I TFTP again, invoking the
name
of the Third Magic File, router-confg. If I succeed, I learn my
True
Name and go to step 8.
7. If I can't get the Third Magic File, I TFTP again for the Fourth
Magic
File, cisconet.cfg. If I don't get this, I go back to Step 3, and
try
again, three times. If I get the Fourth Magic File, I learn my True
Name and go to step 8. If I fail on the third retry, I go to step
9.
No, you don't have to wear ruby slippers and click your heels each
time
you recycle. Admittedly, I'd find it interesting to see how you
a. Put ruby slippers on a router. How many?
b. Click them.
8. I TFTP for the file [True Name].cfg. If I get this, it is my real
real configuration for the router. It tucks this into
NVRAM, then copies it into RAM and starts to run with the new
config.
9. If all else fails, I go into the setup dialogue and hope there's a
nice human at my console.
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