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New Member

Inter AS VPN question

a global question is when using Inter AS VPN , and i am using Private AS , and will be connecting to another provider with Public AS.

do i need to register a public AS alos for this scenario , or i can run the service with my own private AS without having to change it.

taking into consideration that will most probably use VRF-VRF connection as based on RFC 4364

1 ACCEPTED SOLUTION

Accepted Solutions
Cisco Employee

Re: Inter AS VPN question

The AS path on prefixes received from the other AS via BGP on the VRF interface will definitely be propagated via VPNv4 as well as all the other transitive attributes.

Hope this helps,

Harold Ritter
Sr. Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México
Paseo de la Reforma 222
Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México
11 REPLIES
Cisco Employee

Re: Inter AS VPN question

You can indeed use the private AS number as long as the other SP has no problem with it.

Hope this helps,

Harold Ritter
Sr. Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México
Paseo de la Reforma 222
Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México
Silver

Re: Inter AS VPN question

Using the back to back VRF solution, I doubt the other SP would mind. This is because your routes will appear in a vrf on the other SPs router. I doubt the SP will complain about having private addresses in a VRF.

Cisco Employee

Re: Inter AS VPN question

Olorunloba,

I was referring to the private ASN, not the private addresses. In the case of private ASNs, the other SP might have already allocated the private ASN to another of its MPLS VPN customers. Beyond that, it shouldn't be an issue.

Regards,

Harold Ritter
Sr. Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México
Paseo de la Reforma 222
Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México
New Member

Re: Inter AS VPN question

what if the other SP had already allocated the private ASN to another MPLS VPN customer , i guess as per your reply , this also won't affect the case, because this ASN will not be shown in the global routing table , so it won't affect anything. !!

am i right??

New Member

Re: Inter AS VPN question

one thing also appeared in my mind ..

aren't we going to redistribute the routes receieved from BGP into the MP-BGP .will this also transfere the ASN with the route distributed..? if yes , will this also affect the Private ASN assigned , will it make a conflict ?or it will be also within that VPN so will not make any conflict.

Regards

Cisco Employee

Re: Inter AS VPN question

Correct. The prefixes learnt via the bgp session between the two SP networks will be propagated into the SP VPNv4 session along with the private AS. It would only conflict if you were to propagate these updates to a customer using the same ASN to connect to the MPLS VPN network. There is ways such as remove-private-as, as-override or allowas-in to solve this though.

Hope this helps,

Harold Ritter
Sr. Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México
Paseo de la Reforma 222
Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México
New Member

Re: Inter AS VPN question

Thanks for the reply , but why would the ASN be transfered with the VPN-V4 address from the SP1-PE facing the SP2-PE to the remote PE of SP1 ..

i am not sure, but i guess the MP-BGP will transfere only the IP prefexes, VPN-V4 addresses, not any other BGP attribute that were learned with the route in the SP1-PE to SP2-PE BGP session.

Cisco Employee

Re: Inter AS VPN question

The AS path on prefixes received from the other AS via BGP on the VRF interface will definitely be propagated via VPNv4 as well as all the other transitive attributes.

Hope this helps,

Harold Ritter
Sr. Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México
Paseo de la Reforma 222
Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México
New Member

Re: Inter AS VPN question

Thanks so much for the help.

Silver

Re: Inter AS VPN question

Thanks Harold, I was thinking the conversation was about IP addresses.

mohamedhaddad,

Other BGP attributes are also advertised under the eBGP session, in accordance with normal BGP rules. For example, your route-targets communities are also advertised.

Note that if you are using the back-to-back vrf solution, you do not have to use BGP to peer the AS together, and then the BGP attributes will be lost, if this is what you want.

Cisco Employee

Re: Inter AS VPN question

Correct. It shouldn't an issue technically speaking but certain SP might have issues with using the same private ASN for different customers. I guess it boils down to discussing it with the other SP.

Thanks for your reply,

Harold Ritter
Sr. Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México
Paseo de la Reforma 222
Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México
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