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Re: No. of routers carrying full routes?

  • From: Alan Hannan
  • Date: Sun Oct 20 18:37:13 1996

  Hi David,

> Where can I find/how can one estimate the number of routers carrying 
> the full Internet route tables?

  I don't know that this information is readily available....

  I'd guess there are 10 "Big" ISPs w/ an average of 200 Routers
  w/ full tables.

  I'd guess there are 100 Medium ISPs w/ an average of 7 Routers w/ 
  full tables.

  I'd guess there are 25 Companies w/ an average of 3 Routers w/
  full tables.

  (200 * 10) + ( 7 * 100) + (25 * 3) = 2775 ~= 3000 Routers

> I need to convince someone that singly-homed customer route flaps/
> withdrawals should *not* propagate beyond our AS. I've found some 
> discussion of this in the July NANOG archives, and talk about cisco 
> floating statics, etc... and that "one-way" traffic is insignificant.

  Uhm, I'm not sure the concensus was that they shouldn't.  I
  believe most everyone would agree that flaps w/in CIDR blocks
  should not propogate, and that people should only announce the
  most general network possible.

  But, if you've got a customer singly-homed to me, ideally, from an
  architecturely scalable point of view, you would do well to static
  them to your aggregation/POP router.

  However, I'm not sure a quorum agreed that single-homed customers
  should show up in backbone tables if their routes are/were down.

  There are points to be made both ways, but the BB routing tables
  are meant to be a snapshot of the net, and if a vector points to
  provider P, and customer C is not reachable there, I don't really
  think P should announce such....

> I haven't upgraded to 11.1 yet, but my network 
> is simple enough [read: not redundant enough?] that all my customers 
> are singly-connected; in that case, statics in my border routers
> pointing to my customer edge-router seems to make fast install moot 
> for now.

  I assume you're looking forward to dampening?  That would be a very 
  Good Thing.  Hopefully you're not running OSPF/EIGRP/RIP w/ a
  customer and redistributing, but when you start doing BGP w/
  customers (even singly homed ones who migrate address space like
  universities and research institutions) you will have a need for
  dynamic routes, and it may be that static-ing them is an
  administrative headache, with minimal benefit to the
  broken^H^H^H^H^H^H limited Cisco 7xx0s....

> Finally, is there a *searchable* archive of NANOG anywhere?

  Our benevolent friends at Merit promise it soon...


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