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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