At 12:44 PM -0500 1/15/02, Chuck Larrieu wrote:
>interesting question. came up in a customer meeting the other day as well.
>
>IMHO, this gets down to design preference.
Agreed. As you suggest, there's art as well as science here.
>I am of the school of thought
>that there needs be some way of getting to any router in a network ( design
>permitting, cost permitting ), and that each router in a network needs some
>unique and easily identified pneumonic.
>
>So IMHO, one should use loopbacks, numbered according to some rational
>scheme, and that those "routes" should be advertised.IMHO This should be
>true, no matter what routing protocol you are using.
>
>However, others will ask whether in a 5000 router domain, you want 5000
>extra routes in your tables. That is a valid counterargument.
If you have that many routers, you presumably have a hierarchical
design with summarization. Using Cisco's conservative number of
routers per OSPF area, allocate 128 addresses, as part of an
aggregatable block, per area. This gives 39+ blocks.
If one assumes stubby areas, you'd get a maximum of 128 additional
routes per nonzero area, plus 40 extra routes in area 0.0.0.0.
40 areas, however, is a lot for a single OSPF domain. When I've
dealt with networks of this size, I've separated them into multiple
OSPF domains linked by a backbone of backbones, either BGP or
statically routed. That backbone of backbones, of course, gives the
potential for additional aggregation.
>
>Using the RID command under the OSPF process, you can set up a rational
>identification scheme. The RID does not necessarily have to be related to
>interface numbering. But then you have the issue of correlating RIDs to the
>addresses one actually uses to get to the router in question, making it a
>bit more complicated to find things when you need to.
That's why I like the RID to be the "address of last resort" to reach
the router.
>
>JMHO.
>
>Chuck
>
>
>
>
>""john smith"" wrote in message
>[EMAIL PROTECTED]">news:[EMAIL PROTECTED]...
>> Hi,
>> Is there reason one would prefer loopback address for router ID when
using
>> Ospf over the router id command that can be used under "router ospf "
and
>> vice versa. Is there a need to advertise the router IDs in OSPF.
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