Understanding VPLS Routing Instances
To configure VPLS functionality, you must enable VPLS support on the PE router. You must also configure PE routers to distribute routing information to the other PE routers in the VPLS and configure the circuits between the PE routers and the CE devices.
You create a VPLS routing instance on each PE router that is participating in the VPLS. The routing instance has the same name on each PE router. To configure the VPLS routing instance, you specify the following:
- Route distinguisher—Helps BGP distinguish between potentially identical network layer reachability information (NLRI) messages received from different VPLS instances. Each routing instance that you configure on a PE router must have a unique route distinguisher.
- Route target—Defines which route is part of a VPLS. A unique route target helps distinguish between different VPLS services on the same router.
- Site name—Provides unique name for the VPLS site.
- Site identifier—Provides unique numerical identifier for the VPLS site.
- Site range—Specifies total number of sites in the VPLS. The site range must be greater than the site identifier.
- Interface to the CE router—Specifies the physical interface to the CE router that carries VPLS traffic. The interface must be configured for a VPLS encapsulation type.
 | Note: In addition to the VPLS routing instance, you must configure MPLS label-switched paths (LSPs) between the PE routers, internal BGP (IBGP) sessions between the PE routers, and an interior gateway protocol (IGP) on the PE routers. |
 | Caution: MPLS is disabled by default on J Series and SRX Series devices and you must explicitly configure your router to allow MPLS traffic. However, when MPLS is enabled, all flow-based security features are deactivated and the router performs packet-based processing. Flow-based services such as security policies, zones, NAT, ALGs, chassis clustering, screens, firewall authentication, and IPSec VPNs are unavailable on the router. For more information on flow-based and packet-based processing, see the JUNOS Software Security Configuration Guide. |
BGP Signaling
BGP is used to signal the paths between each of the PE routers participating in the VPLS routing instance. These paths carry VPLS traffic across the service provider's network between the VPLS sites.
| Note: LDP signaling is not supported for the VPLS routing instance on J Series or SRX Series devices. |
VPLS Site Name and Site Identifier
When you configure BGP signaling for the VPLS routing instance, you must specify each VPLS site that has a connection to the router. For each VPLS site, you must configure a site name and site identifier (a numerical identifier between 1–65,534 that uniquely identifies the VPLS site).
Site Range
When you enable BGP signaling for the VPLS routing instance, you need to configure a site range. The site range specifies the total number of sites in the VPLS.
| Note: The site range value must be greater than the largest site identifier. |
Site Preference
You can specify the preference value advertised for a particular VPLS site. The site preference value is encoded in the BGP local preference attribute. When a PE router receives multiple advertisements with the same VPLS edge (VE) device identifier, the advertisement with the highest local preference value is preferred.
VPLS Routing Table
The VPLS routing table contains MAC addresses and interface information for both physical and virtual ports. You can configure the following characteristics for the table:
- Table size—You can modify the size of the VPLS MAC
address table. The default table size is 512 MAC addresses; the minimum
is 16 addresses, and the maximum is 65,536 addresses.
If the MAC table limit is reached, new MAC addresses can no longer be added to the table. Eventually the oldest MAC addresses are removed from the MAC address table automatically. This frees space in the table, allowing new entries to be added. However, as long as the table is full, new MAC addresses are dropped.
The interfaces affected include all of the interfaces within the VPLS routing instance, including the local interfaces and the LSI interfaces.
- Timeout interval—You can modify the timeout interval for the VPLS table. The default timeout interval is 300 seconds; the minimum is 10 seconds, and the maximum is 1,000,000 seconds. We recommend you configure longer values for small, stable VPLS networks and shorter values for large, dynamic VPLS networks. If the VPLS table does not receive any updates during the timeout interval, the router waits one additional interval before automatically clearing the MAC address entries from the VPLS table.
- Number of addresses learned from an interface—You
can configure a limit on the number of MAC addresses learned by a
VPLS routing instance by setting the MAC table size. The default is
512 addresses; the minimum is 16, and the maximum is 65,536 addresses.
If the MAC table limit is reached, new MAC addresses can no longer
be added to the table. Eventually the oldest MAC addresses are removed
from the MAC address table automatically. This frees space in the
table, allowing new entries to be added. However, as long as the table
is full, new MAC addresses are dropped.
Because this limit applies to each VPLS routing instance, the MAC addresses of a single interface can consume all the available space in the table, preventing the routing instance from acquiring addresses from other interfaces. You can limit the number of MAC addresses learned from all interfaces configured for a VPLS routing instance, as well as limit the number of MAC addresses learned from a specific interface.
The MAC limit configured for an individual interface overrides the limit configured for all interfaces for the VPLS routing instance. Also, the table limit can override the limits configured for the interfaces.
The MAC address limit applies only to interfaces to CE devices.
Trace Options
The following trace flags display operations associated with VPLS:
- all—All VPLS tracing options
- connections—VPLS connections (events and state changes)
- error—Error conditions
- nlri—VPLS advertisements received or sent using BGP
- route—Trace-routing information
- topology—VPLS topology changes caused by reconsideration or advertisements received from other PE routers using BGP