Subject: router configuration

From: jie weng <[email-masked]>
Date: Wed, 21 Jun 2000 13:52:58 -0700 (PDT)

Hi all,

    I have a question concerning the scope of the 
DHCP protocol.  In RFC (2131) section 1.3, it states
that "DHCP is not intended for use in configuring
routers."  My question is can DHCP be used for router
configuration and if not why?? Thanks

Jie

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From: "Eric A. Hall" <[email-masked]>
Date: Wed, 21 Jun 2000 14:05:56 -0700

> configuration and if not why?? Thanks

Routers are required for relaying bootp/dhcp messages, so you don't want
to configure them with dhcp just like you don't want to configure dhcp
servers with dhcp. If the device' lease expires, all of the downstream
dhcp clients will be negatively affected by it, to say the least.

Given that disclaimer, there is some benefit to be had from it. I would
love to be able to configure my Cisco router's DNS, NTP, and various
other agents using bootp/dhcp instead of having to manually reconfig the
boxes everytime I change my infrastructure. But at the same time, I
certainly wouldn't want the device' addressing services to rely on it.

Unfortunately, there isn't any easy way to decouple configuration data
from an address assignment with DHCP. If you want the icing you have to
take the cake, too. Although I suppose an address could just be held as
a "ticket" without requiring that it be used, the device would also have
to answer to ping and ARP requests to prevent pre-lease queries from
going unanswered.

Not that any of this matters, the last time I tried talking Cisco into
this I got a big shrug.

-- 
Eric A. Hall                                      http://www.ehsco.com/
Internet Core Protocols        http://www.oreilly.com/catalog/coreprot/

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From: Ralph Droms <[email-masked]>
Date: Thu, 22 Jun 2000 17:34:18 -0400

At 01:52 PM 6/21/00 -0700, jie weng wrote:
>In RFC (2131) section 1.3, it states
>configuration and if not why?

We (I think I might be responsible, but who can remember that far back?) 
put that text in to explicitly limit the scope of the original development 
work on DHCP.

So, the protocol police won't come knocking at your hub ("Put down that 
DHCPDISCOVER packet and step away from the LAN segment, please.") if you 
happen to send a DHCP packet to a router.  Just don't count on DHCP to 
auto-architect your internet and configure your routers for you...

- Ralph