The following sections describe the end-to-end solution with BGP PW-routing, assuming appropriate platforms are used for various functions.
Each S-PE and T-PE has a pseudowire routing table that contains a reference to the T-LDP session to use to signal to a set of next hop S-PEs to reach a specific T-PE (or the T-PE if that is the next hop). For VLLs, this table contains aggregated AII Type 2 FECs and may be populated with routes that are learned through MP-BGP or that are statically configured.
MP-BGP is used to automatically distribute T-PE prefixes using the new MS-PW NLRI, or static routes can be used. The MS-PW NLRI is composed of a Length, an 8-byte RD, a 4-byte Global-ID, a 4-byte local prefix, and (optionally) a 4-byte AC-ID. Support for the MS-PW address family is configured in CLI under config>router>bgp>family ms-pw.
MS-PW routing parameters are configured in the config>service>pw-routing context.
To enable support for dynamic MS-PWs on a 7210 node to be used as a T-PE or S-PE, a single, globally unique, S-PE ID, known as the S-PE Address, is first configured under config>service>pw-routing on each 7210 to be used as a T-PE or S-PE. The S-PE Address has the format global-id:prefix. It is not possible to configure any local prefixes used for pseudowire routing or to configure spoke SPDs using dynamic MS-PWs at a T-PE unless an S-PE address has already been configured. The S-PE address is used as the address of a node used to populate the switching point TLV in the LDP label mapping message and the pseudowire status notification sent for faults at an S-PE.
Each T-PE is also be configured with the following parameters:
Global ID
This is a 4 byte identifier that uniquely identifies an operator or the local network.
Local Prefix
One or more local (Layer 2) prefixes (up to a maximum of 16), which are formatted in the style of a 4-octet IPv4 address. A local prefix identifies a T-PE or S-PE in the PW routing domain.
For each local prefix, at least one 8-byte route distinguisher can be configured. It is also possible to configure an optional BGP community attribute.
For each local prefix, BGP then advertises each global ID/prefix tuple and unique RD and community pseudowire using the MS-PW NLRI, based on the aggregated FEC129 AII Type 2 and the Layer 2 VPN/PW routing AFI/SAFI 25/6, to each T-PE/S-PE that is a T-LDP neighbor, subject to local BGP policies.
The dynamic advertisement of each of these pseudowire routes is enabled for each prefix and RD using the advertise-bgp command.
An export policy is also required to export MS-PW routes in MP-BGP. This can be done using a default policy, such as the following.
*A:lin-123>config>router>policy-options# info
----------------------------------------------
policy-statement "ms-pw"
default-action accept
exit
exit
----------------------------------------------However, this would export all routes. A recommended choice is to enable filtering per family, as follows.
*A:lin-123>config>router>policy-options# info
----------------------------------------------
policy-statement "to-mspw"
entry 1
from
family ms-pw
exit
action accept
exit
exit
exit
----------------------------------------------The following command is then added in the config>router>bgp context.
export "to-mspw"Local preference for iBGP and BGP communities can be configured under such a policy.