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BGP-LU

I want to know how BGP-LU work between two different MPLS backbone . Please show me the light with this .

1 Accepted Solution

Accepted Solutions

To summarize, Inter AS option A, B and C are different ways to interconnect two MPLS AS.

 

A. Interconnect via VRF. Each side sees each other as a CE. This option is very secure and very granular, but requires more efforts to manage. It requires a separate BGP session per VRF.

 

B. Interconnect via eBGP VPNv4. The eBGP VPNv4 session is ran between an ASBR in each AS. The ASBRs need to exchange all of the VPNv4 routes for the two ASes, which might be a scaling issue. Easier to manage than option A.

 

C. This option relies on BGP-LU. The ASBR does not need to contain any of the VPNv4 routes, which can be exchanged between route reflectors in each AS. This option can also be used to support L2 VPN services.

 

Cisco also offers a 4th option referred to as option AB, which as its name indicates, is a mix between option A and B. Like option A, it preserves the separate VRFs between the two ASes, but unlike option A, it only requires one BGP session for all the VRFs.

 

For more information you can refer to RFC4363, section 10.

 

https://tools.ietf.org/html/rfc4364#section-10

 

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

View solution in original post

4 Replies 4

Martin L
VIP
VIP

sorry, what is LU ?

Harold Ritter
Cisco Employee
Cisco Employee

BGP Labeled Unicast or in short BGP-LU is commonly used, but not limited to, in an architecture called Unified MPLS. It is used to create an end to end label switched path (LSP) between nodes in different autonomous systems or different domains under the same AS. It does this by carrying labels inside the BGP advertisements for IPv4 or IPv6 unicast prefixes, hence it being called labeled unicast.

 

Please refer to the following document for more information:

 

https://www.cisco.com/c/en/us/support/docs/multiprotocol-label-switching-mpls/multiprotocol-label-switching-mpls/119191-config-unified-mpls-00.html

 

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

Thank you for your explanation . Hence I want to know more about MPLS Inter-AS option A B and C also . Please give me some references . Thank You .

To summarize, Inter AS option A, B and C are different ways to interconnect two MPLS AS.

 

A. Interconnect via VRF. Each side sees each other as a CE. This option is very secure and very granular, but requires more efforts to manage. It requires a separate BGP session per VRF.

 

B. Interconnect via eBGP VPNv4. The eBGP VPNv4 session is ran between an ASBR in each AS. The ASBRs need to exchange all of the VPNv4 routes for the two ASes, which might be a scaling issue. Easier to manage than option A.

 

C. This option relies on BGP-LU. The ASBR does not need to contain any of the VPNv4 routes, which can be exchanged between route reflectors in each AS. This option can also be used to support L2 VPN services.

 

Cisco also offers a 4th option referred to as option AB, which as its name indicates, is a mix between option A and B. Like option A, it preserves the separate VRFs between the two ASes, but unlike option A, it only requires one BGP session for all the VRFs.

 

For more information you can refer to RFC4363, section 10.

 

https://tools.ietf.org/html/rfc4364#section-10

 

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
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