Hey, Alex: At 20:23 27.05.99 +0400, you wrote:

Alex.

First of all, which 'WG' do you mean?

I mean IETF's OSPF WG, sorry :)

Then. I can't understand from your message which kind of hierarchy do you mean. OSPF have a few of different hierarchy issues - (1) two types of metrics, inter and intra-area metrics (type 1 and type 2); (2) there is 2 level hierarchy of AREA/BACKBONE with the summarisation on the area borders.

OK, lemme put it the way it is now: 1. From intra-domain routing standpoint we have two levels: intra-area and inter-area. All routers within an area know the whole topology of it. On the area borders the topology is hidden, routing info summarized and internal routers see summaries from all areas. 2. For routing to destinations outside an OSPF domain we have Type5-LSAs which can carry type 1 or type 2 routes (this is what you meant, I believe), depending on whether your external metric is comparible with the OSPF one or not.

If talking about the first, I hardly imagine the situation when someone is not satisfied by 2 existing metric types (except he can be unsatisfyed by the calculation scheme).

Agree

If about the second - may be, not for ISP (ISP don't use complex OSPF routing, they have a lot of headache with IBGP instead),

I've heard some of them do have big enough OSPF networks :)

but for the corporate networks. Really, why can't I have any-level hierarchy for the OSPF zone - area 0, area 0.1, area 0.1.1, for example (this mean - I built area-0 part; then I add some area 0.1 part - first is _backbone_ in existing terms, second _area_), then if I'd like to add some big part to the area 0.1, I prefere to create sub-area 0.1.1 (for example) instead of building virtual links and using some other tricks

Yeah, in this case the sub-area 0.1.1's topology would be hidden from the 0.1's routers and vice versa.

(moreobver, VL can't be used with CISCO's at all because CISCO don't allow to control router-id directly and you can't build VL withouth

Well, you do know that you can create loopback interfaces and the router-ID will be the highest one among them. Say you do: int lo 0 ip address 255.1.1.1 It will hardly be overriden by another loopback.

knowing router-id; it's amazing why for a few years CISCO can't implement one simple command

router ospf 111 router-id 1.2.3.4

Actually there is a DDTS on the wish-list, but it is still not implemented for some reason, let's hope it will be.... Derek, are you reading us ? ;))

or

router-id Ethernet0

).

Through I think the problem of building complex ara schemas is not important for the ISP. More important is the problem of import/export - I can installl BGP routing with the customer and control announces by the route-map or distribute-lists; I can use RIP (I can't, but it's not important) and control announces by the distribute-lists; why can't I connect the customer's OSPF area (this is area-0 for HIM) to my OSPF network and name his _AREA 1.2.3.4_ with the strict filtering on the border.

I was thinking about it as well. One could configure some area range as a "discard" one, effectively saying that all routes dropping into the range should be ignored instead of announced in a summary-LSA.

This is reason why ISP don't like OSPF and such protocols - they can be used for the inter-router routing, but they can't be used to connect with the customers (no, I can run 10 different OSPF processes and re-advertise routes - one more headache for the network admins).

Actually, you can use NSSA, but doesn't allow for filtering either.

PS. From ISP's point of view. What I'd like.

[snip: got your wish, Alex]

3) Moreover, why can't I determine different BGP AS numbers for the boths ISP and CUST OSPF zones.

who said you can't ? or I'm missing something? Alex.

On Thu, 27 May 1999, Alex Zinin wrote:

...

Date: Thu, 27 May 1999 19:36:13 +0400 From: Alex Zinin <zinin@amt.ru> To: nanog@merit.edu Subject: OSPF multi-level hierarchy: Necessary at all?

Hello,

We're currently discussing necessity of multi-level hierarchy in OSPF on the WG mail list.

The idea is to implement SPF-based interarea routing with more than two levels of topology abstraction and route aggregation (we have two levels in OSPF at the moment level1 being intra-area routing and level2 being the inter-area one).

I have some thoughts on how this could be done, but the main question is whether there is a demand for it or not.

Everyone is really welcome to share opinions.

Thanks in advance, ------------------------------------------------------------------ Alex D. Zinin, Consultant CCSI #98966 CCIE #4015 AMT Group / ISL Cisco Systems Gold Certified Partner http://www.amt.ru irc: //EFNET/#cisco, //irc.msn.com/#NetCisco [Ustas]

Aleksei Roudnev, Network Operations Center, Relcom, Moscow (+7 095) 194-19-95 (Network Operations Center Hot Line),(+7 095) 230-41-41,

N 13729 (pager)

(+7 095) 196-72-12 (Support), (+7 095) 194-33-28 (Fax)

------------------------------------------------------------------ Alex D. Zinin, Consultant CCSI #98966 CCIE #4015 AMT Group / ISL Cisco Systems Gold Certified Partner http://www.amt.ru irc: //EFNET/#cisco, //irc.msn.com/#NetCisco [Ustas]