draft-ietf-dhc-csr-02.txt   draft-ietf-dhc-csr-03.txt 
Network Working Group Ted Lemon Network Working Group Ted Lemon
Internet Draft Nominum, Inc. Internet Draft Nominum, Inc.
Obsoletes: draft-ietf-dhc-csr-01.txt June, 2000 Obsoletes: draft-ietf-dhc-csr-03.txt December, 2000
Expires January 2001 Expires May, 2001
The Classless Static Route Option for DHCP The Classless Static Route Option for DHCP
<draft-ietf-dhc-csr-02.txt> <draft-ietf-dhc-csr-02.txt>
Status of this Memo Status of this Memo
This document is an Internet-Draft and is in full conformance with This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026. all provisions of Section 10 of RFC2026.
This document is an Internet-Draft. Internet-Drafts are working This document is an Internet-Draft. Internet-Drafts are working
skipping to change at line 43 skipping to change at line 43
This document defines a new DHCP option which is passed from the This document defines a new DHCP option which is passed from the
DHCP Server to the DHCP Client to configure a list of static routes DHCP Server to the DHCP Client to configure a list of static routes
in the client. This option supersedes the Static Route option in the client. This option supersedes the Static Route option
(option 33) defined in [2]. (option 33) defined in [2].
Introduction Introduction
The IP protocol [4] uses routers to transmit packets from hosts The IP protocol [4] uses routers to transmit packets from hosts
connected to one IP subnet to hosts connected to a different IP connected to one IP subnet to hosts connected to a different IP
subnet. When an IP host (the source host) wishes to transmit a subnet. When an IP host (the source host) wishes to transmit a
packet to another IP host (the destination), it first checks to see packet to another IP host (the destination), it first checks the IP
if the IP address of the destination host to see if it is on a address of the destination host to see if it is on a subnet to
subnet to which the source host is connected. If the destination which the source host is connected. If the destination host's IP
host's IP address is not on a subnet to which the source host is address is not on a subnet to which the source host is connected,
connected, then the source host consults its routing table to then the source host consults its routing table to determine the IP
determine the IP address of the router that should be used to address of the router that should be used to forward the packet to
forward the packet to the destination host. the destination host.
The routing table on an IP host can be maintained in a variety of The routing table on an IP host can be maintained in a variety of
ways - using a routing information protocol such as RIP [5], ICMP ways - using a routing information protocol such as RIP [5], ICMP
router discovery [6,7] or using the DHCP Router option, defined in router discovery [6,7] or using the DHCP Router option, defined in
[2]. [2].
In a network that already provides DHCP service, using DHCP to In a network that already provides DHCP service, using DHCP to
update the routing table on a DHCP client has several virtues. It update the routing table on a DHCP client has several virtues. It
is efficient, since it makes use of messages that would have been is efficient, since it makes use of messages that would have been
sent anyway. It is convenient - the DHCP server configuration sent anyway. It is convenient - the DHCP server configuration
skipping to change at line 161 skipping to change at line 161
The following table contains some examples: The following table contains some examples:
Subnet number Subnet mask Destination descriptor Subnet number Subnet mask Destination descriptor
0 0 0 0 0 0
10.0.0.0 255.0.0.0 8.10 10.0.0.0 255.0.0.0 8.10
10.17.0.0 255.255.0.0 16.10.17 10.17.0.0 255.255.0.0 16.10.17
10.27.129.0 255.255.255.0 24.10.27.129 10.27.129.0 255.255.255.0 24.10.27.129
10.229.0.128 255.255.255.128 25.10.229.0.128 10.229.0.128 255.255.255.128 25.10.229.0.128
10.198.122.47 255.255.255.255 32.10.198.122.47 10.198.122.47 255.255.255.255 32.10.198.122.47
Local Subnet Routes
In the case where there is more than one IP subnet connected to the
local network, the DHCP server MAY send routes for those subnets
that specify an IP destination address of 0.0.0.0. DHCP clients
that implement this option MUST check for an IP destination address
of 0.0.0.0, and MUST EITHER configure their IP stack to ARP for IP
addresses whose routing destination is 0.0.0.0, OR ignore routes
with a destination of 0.0.0.0. DHCP clients that support ARPing
as described here MUST ignore the Router option (option code 3) if
the Router option contains the client's own IP address.
DHCP Client Behavior DHCP Client Behavior
DHCP clients that do not support this option MUST ignore it if it DHCP clients that do not support this option MUST ignore it if it
is received from a DHCP server. DHCP clients that support this is received from a DHCP server. DHCP clients that support this
option MUST install the routes specified in the option. option MUST install the routes specified in the option. DHCP
clients that support this option MUST NOT install the routes
specified in the Static Routes option (option code 33) if both a
Static Routes option and the Classless Static Routes option are
provided.
DHCP clients that support this option and that send a DHCP DHCP clients that support this option and that send a DHCP
Parameter Request List option MUST request both this option and Parameter Request List option MUST request both this option and the
the Routers option [2] in the DHCP Parameter Request List. Router option [2] in the DHCP Parameter Request List. DHCP clients
that support this option and send a parameter request list MUST NOT
request the Static Routes option.
If the DHCP server returns a Routers option, clients that support If the DHCP server returns a Router option, clients that support
the Classless Static Routes option MUST use the default route(s) the Classless Static Routes option MUST use the default route(s)
listed in the Routers option in addition to the routes listed listed in the Router option in addition to the routes listed
in the Classless Static Routes option. in the Classless Static Routes option.
After deriving a subnet number and subnet mask from each After deriving a subnet number and subnet mask from each
destination descriptor, the DHCP client SHOULD check each route to destination descriptor, the DHCP client SHOULD check each route to
determine if are any bits in the destination network number whose determine if are any bits in the destination network number whose
value is one whose corresponding value in the subnet mask is zero, value is one whose corresponding value in the subnet mask is zero,
and SHOULD NOT install any routes for which this is the case. For and SHOULD NOT install any routes for which this is the case. For
example, the client should not install a route with a destination example, the client should not install a route with a destination
of 129.210.377.4 and a subnet mask of 255.255.255.128. of 129.210.377.4 and a subnet mask of 255.255.255.128.
skipping to change at line 244 skipping to change at line 262
Author Information Author Information
Ted Lemon Ted Lemon
Nominum, Inc. Nominum, Inc.
950 Charter Street 950 Charter Street
Redwood City, CA 94043 Redwood City, CA 94043
email: Ted.Lemon@nominum.com email: Ted.Lemon@nominum.com
Expiration Expiration
This document will expire on January 31, 2001. This document will expire on May 31, 2001.
Full Copyright Statement Full Copyright Statement
Copyright (C) The Internet Society (2000). All Rights Reserved. Copyright (C) The Internet Society (2000). All Rights Reserved.
This document and translations of it may be copied and furnished to This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are kind, provided that the above copyright notice and this paragraph are
 End of changes. 

This html diff was produced by rfcdiff 1.23, available from http://www.levkowetz.com/ietf/tools/rfcdiff/