- play_arrow Common Configuration for All VPNs
- play_arrow VPNs Overview
- play_arrow Assigning Routing Instances to VPNs
- play_arrow Distributing Routes in VPNs
- play_arrow Distributing VPN Routes with Target Filtering
- Configuring BGP Route Target Filtering for VPNs
- Example: BGP Route Target Filtering for VPNs
- Example: Configuring BGP Route Target Filtering for VPNs
- Configuring Static Route Target Filtering for VPNs
- Understanding Proxy BGP Route Target Filtering for VPNs
- Example: Configuring Proxy BGP Route Target Filtering for VPNs
- Example: Configuring an Export Policy for BGP Route Target Filtering for VPNs
- Reducing Network Resource Use with Static Route Target Filtering for VPNs
- play_arrow Configuring Forwarding Options for VPNs
- play_arrow Configuring Graceful Restart for VPNs
- play_arrow Configuring Class of Service for VPNs
- play_arrow Pinging VPNs
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- play_arrow Common Configuration for Layer 2 VPNs and VPLS
- play_arrow Overview
- play_arrow Layer 2 VPNs Configuration Overview
- play_arrow Configuring Layer 2 Interfaces
- play_arrow Configuring Path Selection for Layer 2 VPNs and VPLS
- play_arrow Creating Backup Connections with Redundant Pseudowires
- play_arrow Configuring Class of Service for Layer 2 VPNs
- play_arrow Monitoring Layer 2 VPNs
- Configuring BFD for Layer 2 VPN and VPLS
- BFD Support for VCCV for Layer 2 VPNs, Layer 2 Circuits, and VPLS
- Configuring BFD for VCCV for Layer 2 VPNs, Layer 2 Circuits, and VPLS
- Connectivity Fault Management Support for EVPN and Layer 2 VPN Overview
- Configure a MEP to Generate and Respond to CFM Protocol Messages
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- play_arrow Configuring Group VPNs
- play_arrow Configuring Public Key Infrastructure
- play_arrow Configuring Digital Certificate Validation
- play_arrow Configuring a Device for Certificate Chains
- play_arrow Managing Certificate Revocation
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- play_arrow Configuring Layer 2 Circuits
- play_arrow Overview
- play_arrow Layer 2 Circuits Configuration Overview
- play_arrow Configuring Class of Service with Layer 2 Circuits
- play_arrow Configuring Pseudowire Redundancy for Layer 2 Circuits
- play_arrow Configuring Load Balancing for Layer 2 Circuits
- play_arrow Configuring Protection Features for Layer 2 Circuits
- Egress Protection LSPs for Layer 2 Circuits
- Configuring Egress Protection Service Mirroring for BGP Signaled Layer 2 Services
- Example: Configuring an Egress Protection LSP for a Layer 2 Circuit
- Example: Configuring Layer 2 Circuit Protect Interfaces
- Example: Configuring Layer 2 Circuit Switching Protection
- play_arrow Monitoring Layer 2 Circuits with BFD
- play_arrow Troubleshooting Layer 2 Circuits
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- play_arrow Configuring VPWS VPNs
- play_arrow Overview
- play_arrow Configuring VPWS VPNs
- Understanding FEC 129 BGP Autodiscovery for VPWS
- Example: Configuring FEC 129 BGP Autodiscovery for VPWS
- Example: Configuring MPLS Egress Protection Service Mirroring for BGP Signaled Layer 2 Services
- Understanding Multisegment Pseudowire for FEC 129
- Example: Configuring a Multisegment Pseudowire
- Configuring the FAT Flow Label for FEC 128 VPWS Pseudowires for Load-Balancing MPLS Traffic
- Configuring the FAT Flow Label for FEC 129 VPWS Pseudowires for Load-Balancing MPLS Traffic
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- play_arrow Connecting Layer 2 VPNs and Circuits to Other VPNs
- play_arrow Connecting Layer 2 VPNs to Other VPNs
- play_arrow Connecting Layer 2 Circuits to Other VPNs
- Using the Layer 2 Interworking Interface to Interconnect a Layer 2 Circuit to a Layer 2 VPN
- Applications for Interconnecting a Layer 2 Circuit with a Layer 2 Circuit
- Example: Interconnecting a Layer 2 Circuit with a Layer 2 VPN
- Example: Interconnecting a Layer 2 Circuit with a Layer 2 Circuit
- Applications for Interconnecting a Layer 2 Circuit with a Layer 3 VPN
- Example: Interconnecting a Layer 2 Circuit with a Layer 3 VPN
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- play_arrow Configuration Statements and Operational Commands
VPLS Path Selection Process for PE Routers
The VPLS path selection process is used to select the best path between a remote PE router and a local PE router in a VPLS network. This path selection process is applied to routes received from both single-homed and multi-homed PE routers.
In the VPLS documentation, the word router in terms such as PE router is used to refer to any device that provides routing functions.
When the VPLS path selection process is complete, a PE router is made the designated VPLS edge (VE) device. The designated VE device effectively acts as the endpoint for the VPLS pseudowire that is signaled from the remote PE router. Once a PE router is made the designated VE device, a pseudowire can be signaled between the remote PE router and the local PE router and then VPLS packets can begin to flow between the PE routers.
Routes from multihomed PE routers connected to the same customer site share the same site ID, but can have different route distinguishers and block offsets. You can alter the configurations of the route distinguishers and block offsets to make a router more likely or less likely to be selected as the designated VE device.
On each PE router in the VPLS network, the best path to the CE device is determined by completing the following VPLS path selection process on each route advertisement received:
If the advertisement has the down bit set to 0, the advertisement is discarded.
Select the path with a higher preference. The preference attribute is obtained from the site-preference configured using the
site-preferencestatement at the[edit routing-instances routing-instance-name protocols vpls site site-name]hierarchy level. When the site is down, the preference attribute is obtained from the local preference.If the preference values are the same, select the path with the lower router ID.
If the router IDs are the same, the routes are from the same PE router and the advertisement is considered to be an update. The router ID corresponds to the value of the originator ID for the BGP attribute (if present). Otherwise, the IP address for the remote BGP peer is used.
If the block offset values are the same, the advertisement is considered to be an update.
Once the VPLS path selection process has been completed and the designated VE device has been selected, a pseudowire is signaled between the remote PE router and the local PE router.
The VPLS path selection process works the same whether or not the route has been received from another PE router, a route reflector, or an autonomous system border router (ASBR).
When the remote PE router establishes or refreshes a pseudowire to the local PE router, it verifies that the prefix is in the range required for the site ID based on the block offset and label range advertised by the designated VE device. If the prefix is out of range, the pseudowire status is set to out of range.
The following cases outline the potential decisions that could be made when a PE router completes the VPLS path selection process for a Layer 2 advertisement in the VPLS network:
The PE router originated one of the advertisements and selected its own advertisement as the best path.
This PE router has been selected as the designated VE device. Selection as the designated VE device triggers the creation of pseudowires to and from the other PE routers in the VPLS network. If the remote customer site is multihomed, the designated VE device triggers the creation of pseudowires to and from only the designated VE device for the remote site.
The PE router originated one of the advertisements but did not select its own advertisement as the best path.
This PE router is a redundant PE router for a multihomed site, but it was not selected as the designated VE device. However, if this PE router has just transitioned from being the designated VE device (meaning it was receiving traffic from the remote PE routers addressed to the mulithomed customer site), the PE router tears down all the pseudowires that it had to and from the other PE routers in the VPLS network.
The PE router received the route advertisements and selected a best path. It did not originate any of these advertisements because it was not connected to the customer site.
If the best path to the customer site (the designated VE device) has not changed, nothing happens. If the best path has changed, this PE router brings up pseudowires to and from the newly designated VE device and tears down the pseudowires to and from the previously designated VE device.
If this PE router does not select a best path after running the VPLS path selection process, then the local PE router does not consider the remote site to exist.
When a VE device receives an advertisement for a Layer 2 NLRI that matches its own site ID but the site is not multihomed, the pseudowire between the VE device and the transmitting PE router transitions to a site collision state and is not considered to be up.
