Advanced BGP Configuration

Advanced Options

Default Local Preference:

Configure default Local Preference value (0-4294967295, higher=more preferred)

Table Map:

Uses the specified route map to control how routes received from BGP peers are passed to the dynamic routing manager process, and thus, into routing tables.

Advanced Timers

Coalesce Timer:

Configures the Subgroup coalesce timer, in milliseconds (1-4294967295).

Route Map Delay:

Time to wait (in seconds) before processing route map changes. A value of 0 disables the timer and stops route updates from happening when route maps change.

Dampening:

BGP route flap dampening (RFC 2439) prevents unstable routers from adversely affecting routing behavior.

Time Penalty Half Life:

The time duration during which the stability value will be reduced by half if the route is unreachable.

When to Reuse a Route:

Stability threshold that must be crossed for a route to be reused.

Start Suppressing Route:

Stability threshold that, when crossed, a route will be suppressed.

Max Time to Suppress:

Maximum time to suppress a route considered stable.

Advanced Routing Behavior

Disable Fast External Failover:

Do not immediately reset session if a link to a directly connected external peer goes down.

Network Import Check:

Checks if a BGP network route exists in IGP before creating BGP table entries.

Note

This should be disabled if this router wants to advertise manually summarized routes that do not exist in the routing table, such as collecting all local routes into a larger network in which they can be contained (e.g. 10.14.0.0/16).

Reject AS_SET/AS_CONFED_SET Routes:

Reject incoming and outgoing routes with AS_SET or AS_CONFED_SET type.

Route Reflecting

Route Reflector Outbound:

Allows attributes modified by route maps to be reflected.

Cluster ID:

Route reflector cluster ID.

Disable Client-to-Client:

Disables reflection of routes from one client to another client.

Aggregate Behavior

Configures route aggregation using a list of prefixes. More specific routes contained within the specified prefixes will be aggregated into the larger prefix, minimizing the set of networks advertised to peers.

Aggregate Address:

The prefix to aggregate.

Generate AS Set:

When present, routes for the specified prefix will include an AS set. An AS set is a collection of AS numbers for which routes have been aggregated. This allows peers to detect routing loops, duplicate routes, and so on.

Summary Only:

When present, aggregated routes for this prefix will not be announced, so peers only see the aggregate prefix and not the component networks.

Multi-Exit Discriminator

Deterministic MED:

Determine route selection locally, even when MED values are present. Picks the best MED path from neighbor advertisements.

Always Compare MED:

Instructs the BGP daemon to always consult MED values in routes, no matter which AS the routes were received through.

Max MED:

Administratively applied max MED (Indefinite):

Sends a MED value of 4294967294 at all times.

Definite admin max MED:

Sends this value at all times instead of the default 4294967294.

Time Period for Max MED on startup:

Sends a MED value of 4294967294 at startup for this number of seconds.

Max MED used during startup:

Sends this value at startup instead of the default 4294967294.

Confederation

AS Confederation:

Configures an AS number for the entire group of iBGP routers participating in confederation.

Confederation Peers:

Configures the sub-AS number for the subset of peers inside a group of iBGP routers participating in confederation.

Distance

Administrative Distance:

Manually configures the administrative distance for a given prefix

Define:

The administrative distance for this prefix, from 1-255.

IP Source Prefix:

The IP prefix to which this distance will be applied.

Access List:

An access list which can be used to apply the distance to only a subset of the configured prefix.

BGP Distance:

Configures distance values which control how BGP will treat routes based on the length of their AS path.

AS External Routes:

The distance at which routes are considered external, from 1-255.

AS Internal Routes:

The distance at which routes are considered internal, from 1-255.

Local Routes:

The distance at which routes are considered local, from 1-255.

Best Path Selection

Controls how the BGP daemon determines the best path to a destination.

Compare Path with Confederation:

Considers the length of confederation path sets and sequences.

Ignore AS Path:

Ignores AS path lengths when computing the route to a destination.

Multipath Relax:

Allow Load Sharing:

Consider paths of equal length when choosing between multiple paths to a destination, rather than looking for an exact match. This allows load sharing across different AS paths, so long as they are of equal length.

Generate an AS_SET:

Adds AS set information for aggregate routes.

Compare Router ID:

Uses the router ID of peers (or originator ID, if present) to break ties when computing paths to a destination based on other information. A lower router ID will win in a tie.

MED Confederation:

Compare MED among confederation paths:

Compare confederation path MEDs

Treat missing MED as least preferred path:

If a route is missing MED information, it will be considered least preferred.

eBGP

eBGP Nexthop Connected:

Disable checking if nexthop is an eBGP session.

Enforce First AS:

Enforce the first AS for eBGP routes

Disable eBGP Require Policy:

Disable the requirement to apply incoming and outgoing filter to eBGP sessions.

Networking Behavior

Subgroup Packet Queue:

Maximum size of the subgroup packet queue.

Write Quanta:

Controls the size of peer update transmissions.