Re: [GLOBAL-V6]IPv6 Allocation Policy

["Craig A. Huegen" <chuegen@cisco.com>]

On Wed, 21 May 2003, Pekka Savola wrote:

> So, it seems to me that Cisco would be best using multiple ISP-specific PA
> addresses, right?  That would seem to solve about all the problems related
> to traffic engineering?  (You only configure addresses of those ISP's
> which are connected to your public service sites -- and each of them gets
> there without WAN traffic.)

Actually, it would not.

Multiple PA prefixes as a solution has far too many problems.  I as a
network administrator cannot control the traffic flow -- originating hosts
get to set the network paths by their choices of source/destination
addresses.  The network has no visibility into alternate paths for a TCP
connection -- only the host does, but the host has no information about
preferrable paths on the network.  I have to manage extra prefixes on
every subnet and carry those multiple prefixes in my IGP.  A failure of a
circuit at the edge of the network would trigger an amazingly huge
state-change wave across the network, withdrawing the prefixes from the
interface, then removing them from the IGP.

There are just too many problems in a large network like ours to use the
multi-PA solution.

/cah

-- 
Craig A. Huegen, Chief Network Architect      C i s c o  S y s t e m s
IT Transport, Network Technology & Design           ||        ||
Cisco Systems, Inc., 400 East Tasman Drive          ||        ||
San Jose, CA  95134, (408) 526-8104                ||||      ||||
email: chuegen@cisco.com       CCIE #2100      ..:||||||:..:||||||:..