draft-ietf-ospf-5to7-00.txt   draft-ietf-ospf-5to7-01.txt 
Network Working Group P. Murphy Network Working Group P. Murphy
Internet Draft US Geological Survey Internet Draft US Geological Survey
Expiration Date: November 2001 May 2001 Expiration Date: September 2002 March 2002
File name: draft-ietf-ospf-5to7-00.txt File name: draft-ietf-ospf-5to7-01.txt
OSPF Type 5 to Type 7 Translation Type 5 to Type 7 Translation
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. Internet-Drafts are working all provisions of Section 10 of RFC2026. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas, documents of the Internet Engineering Task Force (IETF), its areas,
and its working groups. Note that other groups may also distribute and its working groups. Note that other groups may also distribute
working documents as Internet-Drafts. working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
skipping to change at page 1, line 39 skipping to change at page 1, line 39
Table Of Contents Table Of Contents
1.0 Abstract ................................................. 1 1.0 Abstract ................................................. 1
2.0 Overview ................................................. 2 2.0 Overview ................................................. 2
2.1 Motivation - Corporate Networks .......................... 2 2.1 Motivation - Corporate Networks .......................... 2
2.2 Proposed Solution ........................................ 2 2.2 Proposed Solution ........................................ 2
3.0 Type 5 Translation Implementation Details ................ 3 3.0 Type 5 Translation Implementation Details ................ 3
3.1 Type 5 Address Ranges .................................... 3 3.1 Type 5 Address Ranges .................................... 3
3.2 Setting the N/P-bit in the Options field of Router-LSAs... 4 3.2 Setting the N/P-bit in the Options field of Router-LSAs... 4
3.3 Calculating Type 7 LSAs as External Routes ............... 4 3.3 Calculating Type 7 LSAs as External Routes ............... 4
3.4 Type 5 Translator Election ............................... 4 3.4 Type 5 Translator Election ............................... 5
4.0 Originating Translated Type 5 LSAs ....................... 5 4.0 Originating Translated Type 5 LSAs ....................... 5
4.1 Translating Type 5 LSAs into Type 7 LSAs ................. 5 4.1 Translating Type 5 LSAs into Type 7 LSAs ................. 5
4.2 Flushing Translated Type 7 LSAs .......................... 8 4.2 Flushing Translated Type 7 LSAs .......................... 8
5.0 Security Considerations .................................. 8 5.0 Security Considerations .................................. 9
6.0 Acknowledgments .......................................... 9 6.0 Acknowledgments .......................................... 9
7.0 References ............................................... 9 7.0 References ............................................... 9
8.0 Author's Address ......................................... 9 8.0 Author's Address ......................................... 9
Appendix A: Configuration Parameters ........................ 10
1.0 Abstract 1.0 Abstract
This memo documents an extension to OSPF which allows area border This memo documents an extension to OSPF which allows area border
routers to translate Type 5 LSAs into Type 7 LSAs with aggregation. routers to translate Type 5 LSAs into Type 7 LSAs with aggregation.
Type 7 LSAs, which are translations of Type 5 LSAs, are flooded into Type 7 LSAs, which are translations of Type 5 LSAs, are flooded into
Not-So-Stubby areas (NSSAs). All differences, while expanding Not-So-Stubby areas (NSSAs). All differences, while expanding
capability, are backward compatible in nature. NSSA Border routers capability, are backward compatible in nature. NSSA Border routers
which run implementations of this memo will interoperate with other which run implementations of this memo will interoperate with other
NSSA routers which do not. This option is only applicable on a NSSA routers which do not. This option is only applicable on a
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2.0 Overview 2.0 Overview
2.1 Motivation - Corporate Networks 2.1 Motivation - Corporate Networks
In a corporate network which supports a large corporate In a corporate network which supports a large corporate
infrastructure it is not uncommon for an OSPF NSSA to support its own infrastructure it is not uncommon for an OSPF NSSA to support its own
internal Internet default. Other areas may have external links to internal Internet default. Other areas may have external links to
outside collaborators. While Type 5 LSAs advertise the existence of outside collaborators. While Type 5 LSAs advertise the existence of
these collaborations throughout the OSPF transit topology, NSSAs with these collaborations throughout the OSPF transit topology, NSSAs with
their own internal default cannot take advantage of these their own internal default route cannot reach take these
collaborations since Type 5 LSAs are not flooded into NSSAs. collaborations through Area 0 since Type 5 LSAs are not flooded into
Consider the following example: NSSAs. Consider the following example:
A0------Area 0 cloud------B0 A0------Area 0 cloud------B0
| | | |
| | | |
Area 2 cloud NSSA 1 cloud Area 2 cloud NSSA 1 cloud
| | | |
| | | |
A2 B1 A2 B1
| | | |
| | | |
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1 respectively. A2 and B1 are ASBRs. A2 advertises a route to 1 respectively. A2 and B1 are ASBRs. A2 advertises a route to
10.0.13.0 through E2 while B1 advertises a preferred Type 7 NSSA 10.0.13.0 through E2 while B1 advertises a preferred Type 7 NSSA
internal default through E1. Since NSSAs do not import Type 5 LSAs, internal default through E1. Since NSSAs do not import Type 5 LSAs,
NSSA 1 has no knowledge of the path through Area 2 to 10.0.13.0/24 NSSA 1 has no knowledge of the path through Area 2 to 10.0.13.0/24
and would instead choose to forward traffic destined to 10.0.13.0/24 and would instead choose to forward traffic destined to 10.0.13.0/24
to its Internet default through E1. to its Internet default through E1.
What is needed is a means of advertising the 10.0.13.0/24 path What is needed is a means of advertising the 10.0.13.0/24 path
through Area 2 into NSSA 1 without converting NSSA 1 to an OSPF through Area 2 into NSSA 1 without converting NSSA 1 to an OSPF
standard area and incurring the full import of all Type 5 LSAs into standard area and incurring the full import of all Type 5 LSAs into
NSSA 1. Currently no such feature exists in OSPF. NSSA 1. Currently no such feature exists in OSPF. It would also be
nice if such a feature supported the aggregation of these external
advertisements to minimize the impact on the size the NSSA's link
state data base.
2.2 Proposed Solution 2.2 Proposed Solution
NSSAs support external routing via Type 7 LSAs. Type 7 LSAs may be NSSAs support external routing via Type 7 LSAs. Destinations
flooded into the larger OSPF domain by translating them into Type 5 described in Type 7 LSAs may be announced to the rest of the larger
LSAs with optional aggregation. The proposed solution to the problem OSPF domain by translating them into Type 5 LSAs with optional
discussed in Section 2.1 is to enable area border routers to have the aggregation. The proposed solution to the problem discussed in
optional capability of translating Type 5 LSAs into Type 7 LSAs and Section 2.1 is to enable area border routers with the optional
then flooding these Type 7 LSAs into their directly attached NSSAs. capability of translating Type 5 LSAs into Type 7 LSAs and then
Type 5 LSA translations are configured separately for each directly flooding these Type 7 LSAs into specific directly attached NSSAs.
attached NSSA as well as what, if any, aggregation is performed. What Type 5 LSAs are translated is configured separately for each
directly attached NSSA as well as what, if any, aggregation is
performed.
The P-bit of a Type 7 LSA translation of a Type 5 LSA is always clear The P-bit of a Type 7 LSA translation of a Type 5 LSA is always clear
so that these translations are never re-translated back into type 5 so that these translations are never re-translated back into Type 5
LSAs by other NSSA border routers. As with the translation of Type 7 LSAs by other NSSA border routers. As with the translation of Type 7
LSAs into Type 5 LSAs, when the result of translating a Type 5 LSA LSAs into Type 5 LSAs, when the result of translating a Type 5 LSA
into a Type 7 LSA is a true aggregation, the forwarding address is into a Type 7 LSA is a true aggregation, the forwarding address is
set to 0.0.0.0. Furthermore, when the import of summary routes into set to 0.0.0.0. Furthermore, when the import of summary routes into
the NSSA is disabled, the forwarding addresses of Type 7 LSA the NSSA is disabled, the forwarding addresses of Type 7 LSA
translations are also 0.0.0.0, since, in this case, the use of non- translations are also 0.0.0.0, since, in this case, the use of non-
zero forwarding addresses would cause the installation failure of zero forwarding addresses would not resolve during the external route
these translations (See the last paragraph of [NSSA] Section 3.5 Step calculation of these translations (See the last paragraph of [NSSA]
(3)). Section 3.5 Step (3)).
3.0 Type 5 Translation Implementation Details 3.0 Type 5 Translation Implementation Details
3.1 Type 5 Address Ranges 3.1 Type 5 Address Ranges
Area border routers may be configured with Type 5 address ranges for Area border routers may be configured with Type 5 address ranges for
each NSSA. Type 5 address ranges are area specific. Each address each NSSA. Type 5 address ranges are NSSA specific. Each address
range is defined as an [address,mask] pair. Many separate Type 5 LSA range is defined as an [address,mask] pair. Many prefixes announced
networks may fall into a single Type 5 address range, just as a in separate Type 5 LSAs may fall into a single Type 5 address range,
subnetted network is composed of many separate subnets. NSSA border just as a subnetted network is composed of many separate subnets.
routers may aggregate Type 5 routes by advertising into the NSSA a E.g. 10.2.2.0/24 and 10.2.3.0/24 fall into the 10.1.0.0/16 range.
single Type 7 LSA for each Type 5 address range. Any Type 5 LSA NSSA border routers may aggregate Type 5 routes by advertising into
translation resulting from a Type 5 address range match will only be the NSSA a single Type 7 LSA for each Type 5 address range. Any
flooded into the NSSA for which the Type 5 address range is Type 5 LSA translation resulting from a Type 5 address range match
configured. Section 4.1 gives the details of generating Type 7 LSAs will only be flooded into the NSSA for which the Type 4 address range
from Type 5 address ranges. is configured. Section 4.1 details how Type 7 LSAs are generated
from Type 5 LSAs and configured Type 5 address ranges.
A Type 5 address range includes the following configurable items. A Type 5 address range includes the following configurable items.
o An [address,mask] pair, o An [address,mask] pair,
o a status indication of either Advertise or DoNotAdvertise, o a status indication of either Advertise or DoNotAdvertise,
o a status indication of either Aggregate or DoNotAggregate, and o a status indication of either Aggregate or DoNotAggregate, and
o an external route tag. o an external route tag.
Any Type 5 LSA which is not contained in a configured Type 5 address Any Type 5 LSA which is not contained in a configured Type 5 address
range of a directly attached NSSA is not translated into a Type 7 range is not translated into a Type 7 LSA. This prevents the
LSA. This prevents the uncontrolled injection of external routing uncontrolled injection of external routing information into NSSAs.
information into NSSAs.
3.2 Setting the N/P-bit in the Options field of Router-LSAs 3.2 Setting the N/P-bit in the Options field of Router-LSAs
NSSA routers as described in [NSSA] expect a Type 7 LSA's non-zero NSSA routers as described in [NSSA] expect a Type 7 LSA's non-zero
forwarding address to have an [NSSA] intra-area path. Type 7 LSA's forwarding address to be resolvable through an NSSA intra-area path.
which are translations of Type 5 LSAs have a non-zero forwarding The forwarding addresses of Type 5 LSAs belong to networks which are
address with an inter-area path. Section A.2 of [OSPF] implies that part of an OSPF standard area. Thus the non-zero forwarding address
the N/P-bit of the router-LSA's Option field of an NSSA router should of a Type 7 LSA translation of any Type 5 LSA has an inter-area path
be set by default. This memo requires that NSSA routers implementing from within its NSSA. Implementations of [OSPF] are expected to set
this option should clear the N/P-bit in their router-LSA's Options the N/P-bit of the router-LSA's Option field of an NSSA router. This
field. NSSA border routers should never translate Type 5 LSAs into memo requires that NSSA routers implementing this option should clear
Type 7 LSAs with non-zero forwarding addresses unless all of the the N/P-bit in their router-LSA's Options field. NSSA border routers
NSSA's router-LSAs have a clear N/P-bit. should never translate Type 5 LSAs into Type 7 LSAs with non-zero
forwarding addresses unless all of the NSSA's router-LSAs have a
clear N/P-bit. If an NSSA's UseForwardingAddresses configuration
parameter (See Appendix A) is set to yes then the N/P-bit of the
NSSA's router LSA is clear. Otherwise the N/P-bit of the NSSA's
router LSA is set.
3.3 Calculating Type 7 LSAs as External Routes 3.3 Calculating Type 7 LSAs as External Routes
The Type 7 LSA External Route calculation discussed in [NSSA] Section The Type 7 LSA External Route calculation discussed in [NSSA] Section
3.5 needs only a minor change to support the translation of Type 5 3.5 needs only a minor change to support the translation of Type 5
LSAs into Type 7 LSAs. In the last paragraph of [NSSA] Section 3.5 LSAs into Type 7 LSAs. In the last paragraph of [NSSA] Section 3.5
Step (3) the non-zero forwarding address of a Type 7 LSA should have Step (3) the non-zero forwarding address of a Type 7 LSA should have
an intra-area path with next-hop through the originating NSSA. The an intra-area path with next-hop through the originating NSSA. The
non-zero forwarding addresses of Type 5 LSAs, as well as their Type 7 non-zero forwarding addresses of Type 5 LSAs, as well as their Type 7
translations, are normally external to an NSSA. In Section 3.5 Step translations, are normally external to an NSSA. In Section 3.5 Step
(3), if all of the NSSA's router-LSAs have a clear N/P-bit in their (3), if all of the NSSA's router-LSAs have a clear N/P-bit in their
Options field, then non-zero forwarding addresses of Type 7 LSAs Options field, then non-zero forwarding addresses of Type 7 LSAs
which originate from one of the NSSA's border routers must be allowed which originate from one of the NSSA's border routers must be allowed
to have inter-area paths with next-hop through the originating NSSA. to have inter-area paths with next-hop through the originating NSSA.
Otherwise they should ignore these LSAs. Otherwise they should ignore these LSAs.
Even with the above change, the Type 7 AS external route calculation Even with the above change, on NSSA border routers the Type 7 AS
of a Type 5 LSA translation with a non-zero forwarding address fails external route calculation of a Type 5 LSA translation with a non-
on NSSA border routers in the last paragraph of Section 3.5 Step (3) zero forwarding address fails in the last paragraph of Section 3.5
allowing the Type 5 LSA from which it was translated to be preferred. Step (3) allowing the Type 5 LSA from which it was translated to be
However, since Type 5 LSAs must choose their preferred paths through preferred. However, since Type 5 LSAs must choose their preferred
the transit topology as discussed in [NSSA] Section 3.5 Step (3), paths through the transit topology as discussed in [NSSA] Section 3.5
their Type 7 LSA translations which have a 0.0.0.0 forwarding address Step (3), their Type 7 LSA translations which have a 0.0.0.0
and Type-1 metric may offer a more preferred path through the forwarding address and Type-1 metric may offer a more preferred path
originating NSSA. through the originating NSSA.
3.4 Type 5 Translator Election 3.4 Type 5 Translator Election
It may be desirable to have only one Type 5 border router translator. It may be desirable to have only one Type 5 border router translator.
For the sake of simplicity this specification combines the duties of For the sake of simplicity this specification combines the duties of
translating Type 5 LSAs into Type 7 LSAs with the duties of translating Type 5 LSAs into Type 7 LSAs with the duties of
translating Type 7 LSAs into Type 5 LSAs. Any configured or elected translating Type 7 LSAs into Type 5 LSAs. Any configured or elected
translator of Type 7 LSAs into Type 5 LSAs will also translate Type 5 translator of Type 7 LSAs into Type 5 LSAs will also translate Type 5
LSAs into Type 7 LSAs. There are no other NSSA border router LSAs into Type 7 LSAs. There are no other NSSA border router
translators. translators.
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[address,mask] pair is more specific than the [address,mask] pairs of [address,mask] pair is more specific than the [address,mask] pairs of
other Type 5 ranges which contain the LSA's network. other Type 5 ranges which contain the LSA's network.
When a Type 5 LSA is translated without aggregation (See Step (2) When a Type 5 LSA is translated without aggregation (See Step (2)
below), its Type 7 LSA translation uses the Type 5 LSA's non-zero below), its Type 7 LSA translation uses the Type 5 LSA's non-zero
forwarding address and metrics provided the following two conditions forwarding address and metrics provided the following two conditions
are met: are met:
o summary routes are imported, o summary routes are imported,
o all of the NSSA's router-LSAs have the N/P bit clear in the o all of the NSSA's router-LSAs, including the local router, have
router-LSA's Options field. the N/P bit clear in the router-LSA's Options field.
Otherwise the Type 7 LSA's forwarding address must be 0.0.0.0 and its Otherwise the Type 7 LSA's forwarding address must be 0.0.0.0 and its
metrics are recomputed using the originating NSSA router as the metrics are recomputed using the originating NSSA border router as
source (See below). the source (See below).
For each translation eligible Type 5 LSA perform the following for For each translation eligible Type 5 LSA perform the following for
each directly attached NSSA: each directly attached NSSA:
(1) If the Type 5 range which best matches the Type 5 LSA's (1) If the Type 5 range which best matches the Type 5 LSA's
network has DoNotAdvertise status or if the LSA is not network has DoNotAdvertise status or if the LSA is not
contained in any explicitly configured Type 5 address range contained in any explicitly configured Type 5 address range
then do nothing with this Type 5 LSA and consider the next one then do nothing with this Type 5 LSA and consider the next one
in the list. Otherwise term the LSA as translatable and in the list. Otherwise term the LSA as translatable and
proceed with step (2). proceed with step (2).
(2) If the Type 5 range which best matches the Type 5 LSA's (2) If the Type 5 range which best matches the Type 5 LSA's
network has DoNotAggregate status and the translated Type 5 network has DoNotAggregate status and the translated Type 5
would have a 0.0.0.0 forwarding address or the calculating would have a 0.0.0.0 forwarding address or the forwarding
router has the highest router ID amongst NSSA translators address is non-zero and the calculating router has the highest
which have originated a functionally equivalent Type 7 LSA router ID amongst NSSA translators which have originated a
(i.e. same destination, cost and non-zero forwarding address) functionally equivalent installed Type 7 LSA (i.e. same
and which are reachable over area 0, then a Type 7 LSA should destination, cost and non-zero forwarding address) and which
be generated with the appropriate forwarding address (See are reachable over area 0, then a Type 7 LSA should be
above) provided there currently is no Type 7 LSA originating generated with the appropriate forwarding address (See above)
from this router corresponding to the Type 5 LSA's network or provided there currently is no Type 7 LSA originating from
there is an existing Type 7 LSA and either it corresponds to a this router corresponding to the Type 5 LSA's network or there
local OSPF external source whose path type and metric is less is an existing Type 7 LSA and either it corresponds to a local
OSPF external source whose path type and metric is less
preferred (see [NSSA] Section 3.5 step (6)) or it doesn't and preferred (see [NSSA] Section 3.5 step (6)) or it doesn't and
the Type 7 LSA's path type or cost(s) have changed (See [NSSA] the Type 7 LSA's path type or cost(s) have changed (See [NSSA]
Section 3.5 step (5)), or its non-zero forwarding address is Section 3.5 step (5)), or its non-zero forwarding address is
no longer reachable or its usage status of a non-zero no longer reachable or the use of non-zero forwarding
forwarding address has changed (See above). addresses has changed (See above).
The newly originated Type 7 LSA will describe the same network The newly originated Type 7 LSA will describe the same network
and have the same network mask, path type and external route and have the same network mask, path type and external route
tag as the Type 5 LSA. The advertising router field will be tag as the Type 5 LSA. The advertising router field will be
the router ID of this NSSA border router. The P-bit will be the router ID of this NSSA border router. The P-bit will be
clear. If the Type 7 LSA's forwarding address will be non- clear. If the Type 7 LSA's forwarding address will be non-
zero the newly originated Type 7 LSA will have the same metric zero the newly originated Type 7 LSA will have the same metric
as the Type 5 LSA. Otherwise the metric is set as follows: as the Type 5 LSA. Otherwise the metric is set as follows:
o when the path type is Type-2 add 1 to the Type 5 LSA's o when the path type is Type-2 add 1 to the Type 5 LSA's
metric, metric,
o when the path type is Type-1 the link state cost of the o when the path type is Type-1 the routing table cost of
Type 5 LSA's network is used. the Type 5 LSA's network is used.
When the path type is Type-2, 1 is added to the Type 5 LSA's When the path type is Type-2, 1 is added to the Type 5 LSA's
metric to ensure that the translated Type 7 LSA is not more metric to ensure that the translated Type 7 LSA is not more
preferred on the NSSA border than a translatable Type 5 LSA preferred on the NSSA border than a translatable Type 5 LSA
whose network has the same [address,mask] pair and Type-2 whose network has the same [address,mask] pair and Type-2
metric. The link-state ID is equal to the LSA's network metric. The link-state ID is equal to the LSA's network
address (in the case of multiple originations of Type 5 LSAs address (in the case of multiple originations of Type 5 LSAs
with the same network address but different mask, the link- with the same network address but different mask, the link-
state ID can also have one or more of the range's "host" bits state ID can also have one or more of the range's "host" bits
set). set).
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metric for this Type 5 range as described below. metric for this Type 5 range as described below.
The path type and metric of the Type 5 range is determined The path type and metric of the Type 5 range is determined
from the path types and metrics of those translatable Type 5 from the path types and metrics of those translatable Type 5
LSAs which best match the range plus any locally sourced Type LSAs which best match the range plus any locally sourced Type
7 LSAs whose network has the same [address,mask] pair. If any 7 LSAs whose network has the same [address,mask] pair. If any
of these LSAs have a path type of 2 then the range's path type of these LSAs have a path type of 2 then the range's path type
is 2, otherwise it is 1. If the range's path type is 1 its is 2, otherwise it is 1. If the range's path type is 1 its
metric is the highest link state cost amongst these LSAs; if metric is the highest link state cost amongst these LSAs; if
the range's path type is 2 its metric is the highest Type-2 the range's path type is 2 its metric is the highest Type-2
metic + 1 amongst these LSAs (See [NSSA] Section 3.5 step metric + 1 amongst these LSAs (See [NSSA] Section 3.5 step
(5)). One is added to the Type-2 metric to ensure that the (5)). One is added to the Type-2 metric to ensure that the
translated Type 7 LSA is not more preferred on the NSSA border translated Type 7 LSA is not more preferred on the NSSA border
than a translatable Type 5 LSA whose network has the same than a translatable Type 5 LSA whose network has the same
[address,mask] pair and Type-2 metric. [address,mask] pair and Type-2 metric.
A Type 7 LSA is generated from the Type 5 range when there A Type 7 LSA is generated from the Type 5 range when there
currently is no Type 7 LSA originated by this router whose currently is no Type 7 LSA originated by this router whose
network has the same [address,mask] pair as the range or there network has the same [address,mask] pair as the range or there
is but either its path type or metric has changed or its is but either its path type or metric has changed or its
forwarding address is non-zero. forwarding address is non-zero.
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to the Type 5 range's address (in the case of multiple to the Type 5 range's address (in the case of multiple
originations of Type 7 LSAs with the same network address but originations of Type 7 LSAs with the same network address but
different mask, the link-state ID can also have one or more of different mask, the link-state ID can also have one or more of
the range's "host" bits set). The advertising router field the range's "host" bits set). The advertising router field
will be the router ID of this NSSA border router. The network will be the router ID of this NSSA border router. The network
mask and the external route tag are set to the Type 5 range's mask and the external route tag are set to the Type 5 range's
configured values. The P-bit will be clear. The forwarding configured values. The P-bit will be clear. The forwarding
address is set to 0.0.0.0. The path type and metric are set address is set to 0.0.0.0. The path type and metric are set
to the Type 5 range's path type and metric as defined above. to the Type 5 range's path type and metric as defined above.
(4) If a Type 5 range match has occurred, the pending processing Note that when a Type 5 range match does occur, the subsequent
of other translation eligible Type 5 LSAs which best match processing of other translation eligible Type 5 LSAs which best match
this Type 5 range is suppressed. Thus at most a single Type 5 the Type 5 range is suppressed. Thus at most a single Type 5 LSA is
LSA is originated for each Type 5 range. originated for each Type 5 range.
For example, given a Type 5 range of [10.0.0.0, 255.0.0.0] which For example, given a Type 5 range of [10.0.0.0, 255.0.0.0] which
subsumes the following Type 5 routes: subsumes the following Type 5 routes:
10.1.0.0 path type 1, link state cost 10 10.1.0.0 path type 1, link state cost 10
10.2.0.0 path type 1, link state cost 11 10.2.0.0 path type 1, link state cost 11
10.3.0.0 path type 2, metric 5, 10.3.0.0 path type 2, metric 5,
a Type 7 LSA would be generated with a path type of 2 and a metric 6. a Type 7 LSA would be generated with a path type of 2 and a metric 6.
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allows a Type 5 range to apply different properties (aggregation, allows a Type 5 range to apply different properties (aggregation,
forwarding address, and Advertise/DoNotAdvertise status) for the Type forwarding address, and Advertise/DoNotAdvertise status) for the Type
5 routes it subsumes, versus those Type 5 routes subsumed by other 5 routes it subsumes, versus those Type 5 routes subsumed by other
more specific Type 5 ranges contained by the Type 5 range. more specific Type 5 ranges contained by the Type 5 range.
4.2 Flushing Translated Type 5 LSAs 4.2 Flushing Translated Type 5 LSAs
If an NSSA border router has either translated or aggregated an If an NSSA border router has either translated or aggregated an
installed Type 5 LSA into a Type 7 LSA and that Type 5 LSA is no installed Type 5 LSA into a Type 7 LSA and that Type 5 LSA is no
longer translatable, then the Type 7 LSA should either be flushed or longer translatable, then the Type 7 LSA should either be flushed or
reoriginated as an aggregation of other Type 5 LSAs. reoriginated as a translation or aggregation of other Type 5 LSAs.
If an NSSA border router is translating Type 5 LSAs into Type 7 LSAs If an NSSA border router is translating Type 5 LSAs into Type 7 LSAs
with with
NSSATranslatorState = elected NSSATranslatorState = elected
and the NSSA border router has determined that its translator and the NSSA border router has determined that its translator
election status has been deposed by another NSSA border router, then, election status has been deposed by another NSSA border router, then,
as soon as the TranslatorStabilityInterval (See [NSSA] Section 4.1) as soon as the TranslatorStabilityInterval (See [NSSA] Section 4.1)
has expired without the router reelecting itself as a translator, any has expired without the router reelecting itself as a translator, any
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This memo does not create any new security considerations for the This memo does not create any new security considerations for the
OSPF protocol. Security considerations for the base OSPF protocol OSPF protocol. Security considerations for the base OSPF protocol
are covered in [OSPF]. are covered in [OSPF].
6.0 Acknowledgments 6.0 Acknowledgments
This document was produced by the OSPF Working Group, chaired by John This document was produced by the OSPF Working Group, chaired by John
Moy. Moy.
In addition, the comments of the following individual is also Most notably, Alex Zinin of Nexsi is acknowledge for suggesting that
acknowledged: translating Type 5 LSAs into Type 7 LSAs would be a useful feature
and has provided substantial technical review in the preparation of
Alex Zinin cisco the document.
7.0 References 7.0 References
[NSSA] R. Colton, V. Fuller, P. Murphy, "The OSPF NSSA Option", RFC [NSSA] R. Colton, V. Fuller, P. Murphy, "The OSPF NSSA Option", RFC
TBD, March 2001. TBD, March 2001.
[OSPF] Moy, J., "OSPF Version 2", RFC 2328, Cascade Communications [OSPF] Moy, J., "OSPF Version 2", RFC 2328, Cascade Communications
Corp., April 1998. Corp., April 1998.
8.0 Authors' Addresses 8.0 Authors' Addresses
Pat Murphy Pat Murphy
US Geological Survey US Geological Survey
345 Middlefield Road 345 Middlefield Road
Menlo Park, California 94560 Menlo Park, California 94560
Phone: (415) 329-4044 Phone: (415) 329-4044
EMail: pmurphy@noc.doi.net EMail: pmurphy@noc.usgs.net
Appendix A: Configuration Parameters
Section 3.1 of this document lists the configuration parameters
for Type-5 address ranges. The following area configuration
parameter has been added and should be configurable for each
directly connected NSSA.
UseForwardingAddrresses
If set to yes an NSSA router will originate a router-LSA with a
clear N/P-bit. Otherwise it will originate a router-LSA with
the N/P bit set. On NSSA internal routers the default setting
is yes. On NSSA border routers the default setting is yes when
the NSSA parameter ImportSummaries is enabled. The default
setting is no when ImportSummaries is disabled.
 End of changes. 

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