From: Gabriel Nunes (gabriel.nunes@gmail.com)
Date: Thu Jan 31 2008 - 14:55:55 ARST
Thanks Scott,
You caught my point. What we have here is different and makes part of the
evolution. We are used with backbones which already had a BGP configured and
was migrated to MPLS, or we have ISP's that already had BGP configured as
well.
Now we have a mobile phone provider wishing to extended its services to the
corporative world. They will firstly lauch a Voice solution called "Class
5". It is a CPE connected to a IP PABX, and this CPE will talk SIP with the
Softswitch and RTP with the Media gateways.
Once they have an CPE on the customer house they will attack the VPN
service, and they already have a power MPLS for this.
So this is new, mainly for the Engineering which has Voice experts and not
IP experts. This is why I have to prove them the need of an Public AS on the
backbone.
I have raised the following points and I sent this e-mail to the group in
order to check if anyone knows any other strong impact. I think they are
seeing this as a "flexibility point". The points are:
*- Avoid routing issues with customers that wish to stablish BGP session
with the CE. The private AS may overlap with some AS configured on the
customer network or with some other Service Provider which the customer may
be connected.*
**
*- The VPNv4 address, is built by IPv4 + RD (Route Distinguer). The
structure of this value can be either ASN:nn or IP-address:nn. It is
recommended to use ASN:nn with an Autonomous System Number (ASN) that is
assigned by the Internet Assigned Numbers Authority (IANA) so that it is
unique between service providers. when the MPLS/VPN network uses a private
AS number it is recommended to use the IP-address:nn format only but the
VPN-IPv4 addresses are propagated beyond the private AS (for example, when
exchanging VPN routes between different service providers). Because the
customers who use the routes contained within the VRF also can attach to
other MPLS/VPN service providers, it is important to use the ASN of the
service provider as the first two bytes of the route distinguisher format to
avoid using the same VPN-IPv4 addresses in separate MPLS/VPN domains.*
**
*- The mandatory use of a public address on the PE-CE meshing and CE
Loopback (management). would belong to some ISP, which means that the
network will be dependent of this ISP as there will be no workaround to
change all the addressing in the future.*
*If the mobile phone provider wishes to become an ISP in the future. The
private AS will influence on the internet VPN provisioning.
*
Thanks you all. If you have any other suggestion...
Gabriel Nunes CCIE#17737
On Jan 31, 2008 1:29 PM, Scott Morris <smorris@ipexpert.com> wrote:
> I suppose that depends on who you are going to peer with and what their AS
> numbers are.
>
> While public AS numbers are good because you have a relative guarantee of
> no
> overlap, it's not always necessary. As a mobile phone provider, I'm
> having
> a hard time visualizing who you would peer with that would not be a public
> AS already. (e.g. real ISPs and not end customers)
>
> But otherwise, situations like these are why we have exciting technologies
> such as BGP Confederations or the Local-AS command set!
>
> If you're worried about overlap on AS numbers, don't pick the obvious
> ones!
> Most docs have 64512-64519 or 65000-65009 in them. Don't use those. Pick
> something like 64739 or some weird number like that and your chances of
> overlap are statistically reduced.
>
> Cheers,
>
>
> Scott Morris, CCIE4 (R&S/ISP-Dial/Security/Service Provider) #4713,
> JNCIE-M
> #153, JNCIS-ER, CISSP, et al.
> CCSI/JNCI-M/JNCI-ER
> VP - Technical Training - IPexpert, Inc.
> IPexpert Sr. Technical Instructor
>
> A Cisco Learning Partner - We Accept Learning Credits!
>
> smorris@ipexpert.com
>
>
>
> Telephone: +1.810.326.1444
> Fax: +1.810.454.0130
> http://www.ipexpert.com
>
>
>
>
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> Gabriel Nunes
> Sent: Wednesday, January 30, 2008 9:20 AM
> To: Cisco certification
> Subject: Public or Private AS
>
> Hi Experts!
>
> I work for a mobile phone provider which is intending to provide VPN MPLS
> service that require the use of MP-BGP protocol into the backbone MPLS.
>
> The question is regarding the AS number to use in the backbone. I believe
> that they need to configure a public AS instead of a private AS to avoid
> some kind of overlapping issues with the customer, and BGP AS-Path issues
> as
> well.
> I'd like to hear from your side the key technical points to justify the
> use
> of a public AS in the backbone for this service. Any?
>
> Thanks,
>
> Gabriel Nunes CCIE#17737
>
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