# BGP Virtual Router Settings

The Border Gateway Protocol (BGP) is a routing protocol for communication between autonomous systems (ASs) on the Internet. You can create and configure a BGP routing instance on your NetScreen device. Note that a virtual router (such as the trust-vr) can have only one BGP routing instance at a time.

### To Create or Edit a BGP Routing Instance

1. Enter the necessary information:

AS Number: Enter a value for the AS to which the current BGP routing instance belongs. The value can be any valid integer.

Keep Alive: Specifies the number of seconds between keepalive packet transmissions sent by the BGP routing instance to its peer.Select one of the following:

Use node default: Sets the keepalive transmission interval to 1/3 of the hold time value.

Custom: Sets the keepalive transmission interval to the value entered.

Always compare MED state: Select this feature if you want each entry point into the AS to be compared with all others to determine its level of relative desirability as a path into the AS. The entry point with the lowest value is the most desirable. The routing instance designates the most desirable entry point as the default path into the AS from other routing domains. This method is known as the Multi_Exit_Discriminator comparison.

Route flap damping state: Select whether the current BGP routing instance suppresses route advertising by an unstable router on the network. If a router in a pattern of failing and enabling continues to advertise itself and its routes as alternatively available and unavailable, it floods the network with invalid advertisements, an activity known as route flapping. Select this check box to block advertisements of a flapping route.

Ignore default route from peer: Select this option to ignore the default route from the peer.

Advertise default route: Select this option to ignore the default route from the peer.

Hold Time: Select one of the following check boxes:

Disable: Disables the hold time.

Enable: Enables the hold time. Enter a value that is the amount of time that elapses between message transmissions between the current BGP virtual routing instance and its BGP neighbor. The value can be any valid integer.

Default local preference: Enter the preference value for the AS path for BGP updates going into the current virtual routing instance.

Default MED: Enter the default Multi_Exit_Discriminator value on the current BGP virtual routing instance. The Multi_Exit_Discriminator is a BGP attribute that determines the relative preference of entry points into an AS.

Route reflector: Select whether you want the current BGP routing instance to act as a route reflector or a device that advertises routes incoming to the current AS to clients in a designated reflector cluster. The radio button choices are Enable and Disable.

Cluster ID: Enter a value that indicates the ID number identifying the group of routing instances that comprises both the route reflector and the reflector clients to which the route reflector advertises all learned routes entering the current AS from an external routing domain.

Synchronize with IGP: Select this feature to synchronize with IGP.

BGP Enabled: Select whether the current BGP routing instance is in the enabled state. BGP routing instances can be in one of two states: enabled or disabled. The default is disabled. To have an active BGP virtual routing instance, you must enable it.

2. Click OK to save your changes and return to the Virtual Router Basic Configuration page. Click Apply to continue configuring the BGP routing instance.

If you clicked Apply, the following links appear at the top of the page: Confederation, Networks, Community, Redist. Rules, Aggregate Address, Neighbors, Peer Group, and AS Path.

## Other Configurations

After you create a BGP routing instance, you can perform the following configurations:

### To Configure a Confederation

To configure BGP confederations, see BGP Confederations.

### To Specify Reachable Networks

To specify networks that are reachable from the virtual router, see BGP Network Setting Configuration.

### To Configure BGP Communities

To configure BGP communities, see BGP Communities.

### To Configure Redistribution Rules

To configure conditions to redistribute routes to the current BGP router, see BGP Redistribution Rules.

### To Configure an Aggregate Address

To configure an aggregated BGP address, see BGP Aggregation.

### To Configure BGP Neighbors

To configure BGP neighbors, see BGP Peers.

### To Configure BGP Peer Groups

To configure BGP peer groups, see BGP Peer Groups.

### To Configure an AS-Path Access List

To configure an AS-PATH access list, see BGP AS-Path Access List.