Tim Franklin wrote:
On Thu, August 21, 2008 12:59 am, Brandon Price wrote:
Other than just saying "its bad" can you give some specifics as to the
problems you've run into using private addresses for PE-CE links? As
long as the SP hands out unique addresses across all of the links, what
does it matter whether they are "private" or "public" ?
Customers using *all* of RFC1918 space (or at least claiming they do).
e.g. if you have WAN links as /30s out of 10.11.12.0/24, and the customer
has that range on a LAN somewhere, each site will be unable to reach the
particular hosts on it's WAN /30. (At least - if you're redistributing
WAN routes into BGP / MBGP, the lack of visibility gets worse).
Most[1] large telcos I've seen[2] offering IP-VPN services tend to use
RFC1918 addressing for CE-PE infrastructure. Using public addressing
for much of this just often doesn't scale - thinking of some IP-VPNs
which have thousands of CE elements.
Most of them make this clear when doing the pre-sales design work, and
have very clear exclusion lists for prefixes that *will not* be accepted
into the IP-VPN under any circumstances. The majority of customers I've
worked with have been comfortable with this, given that it's generally a
small number of /30s or /31s and very rarely (in fact, I can't think of
a time) is there a conflict. In the odd case, if the customer refuses
to work with the telco.... the telco will just not accept the customer
without doing some form of Network Special Deal which results in the
customer paying a whole bunch more for the service to cover the
deviation costs.[3]
My own employer, a multinational in 100+ countries, uses RFC1918
extensively but our WAN group has managed to work around conflicts with
the multitude of IP-VPN services that use RFC1918 on the WAN.
aj
[1] Obviously this doesn't include all of them. I have a couple of
IP-VPNs which do make use of public /31 infrastructure but this is rare.
I have a feeling that these /31s may be re-used across multiple IP-VPN
services.
[2] I tend to have a slightly incumbent/tier 1 view of the world.
[3] This is usually *very* expensive for the customer. If the customer
wants it bad enough... they'll pay.... but see [2]. :)
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