MPLS L2VPN BGP Signaled Pseudowires
- P, PE, and CE Routers
- Attachment Circuits
- Ethernet and Ethernet-VLAN Encapsulation
- Kompella Circuits
- Route Targets
- Route Distinguishers
- Site IDs
- Label Block
Attachment circuit is the logical connection between a CE and a PE.
With VLAN Tags, there can be many attachment circuits on a single wire.
Encapsulation type for CE-facing interface : Ethernet, Ethernet-VLAN
Every BGP VPN Route advertisement consists of two parts
-
NLRI Network Layer Reachability Information
-
BGP Attributes
L2VPN Address Familty (AFI 25 , SAFI 65)
AFI: Layer-2 VPN (25)
SAFI: VPLS (65)
Remote PEs are auto discovered, no need of explicit configuration
If an attachment circuit is migrated to a different PE, the other PE will autodiscover the change.
Route Target : imports/exports advertisements into/out of VPN
Site ID: unique identifier for each end of the L2VPN, used to calculate VPN Label
Label Block: advertises a range of labels for multiple attachment circuits at the same site; calculated using Label Base, Size, Offset, and the Site ID
Route Distinguisher Formats:
- Type 0 (2B+4B+NLRI) Uses 2B ASN
64512:1234567:10.10.10.0/24
- Type 1 (4B+2B+NLRI) Uses IP, Recommended by RFC
192.168.1.1:12345:10.10.10.0/24
- Type 2 (4B+2B+NLRI) (Uses 4B ASN)
4200000000:12345:10.10.10.0/24
Type 1 enables faster failover.
Pre-requisites for creating an L2VPN
- IS-IS or OSPF in the core
- MPLs LSPs between PEs (LDP or RSVP) (populates
inet.3table) - BGP between PEs (via route reflector) with
family l2vpn signalling
Idle, Connect, Active, OpenSent, OpenConfirmed,Established
Route Target, Site ID, Label Base/Size/Offset, Route Distinguisher, VPN Label, Encapsulation
For Standard BGP, IPv4
RIB-IN –> RIB-Local —> RIB-OUT
RIB-Local: inet.0
With L2VPNs (AFI/SAFI 25/65), we create a routing instance
bgp.l2vpn.0 —> <instance-name>.l2vpn.0 —>
Transport label is resolved in mpls.0 table
Layer 2 Information Community
There is another table named <instance-name>.l2id.4.
