13.1.5 BGP4 important reminder for use

RFC 4271

Path attribute: NEXT_HOP

If the external peer to which the route is being advertised shares a subnet with one of the interfaces of the announcing BGP speaker, the speaker may use the IP address associated with such an interface in the NEXT_HOP attribute. This is known as a "first party" NEXT_HOP attribute.

The "first party" NEXT_HOP attribute is not supported.

When sending a message to an external peer, and the peer is multiple IP hops away from the speaker (also known as a "multihop EBGP"), the BGP speaker may be configured to propagate the NEXT_HOP attribute without modification.

The Switch changes the NEXT_HOP attribute to the address of the local router when advertising a route to an external peer.

Path attribute: MULTI_EXIT_DISC

A BGP speaker must implement a mechanism (based on local configuration) that allows the MULTI_EXIT_DISC attribute to be removed from a route. If a BGP speaker is configured to remove the MULTI_EXIT_DISC attribute from a route, then this removal must be done prior to determining the degree of preference of the route and prior to performing route selection.

A mechanism for removing the MULTI_EXIT_DISC attribute from a route is not implemented.

Connection collision detection

Upon receipt of an OPEN message, the local system must examine all of its connections that are in the OpenConfirm state. The local system also examines connections in an OpenSent state if it knows the BGP identifier of the peer by some means outside the protocol.

Upon receipt of an OPEN message, the Switch examines all connections that are in the OpenSent state or Connect state.

BGP FSM: Idle state

For a peer that has previously transitioned to the Idle state because of an error, the time between consecutive generations of Start events (if such events are generated automatically) must increase exponentially. The value of the initial timer is 60 seconds. The time is doubled for each consecutive retry.

The first timer between Idle status and start is 16 to 36 seconds.

BGP FSM: Active state

If the transport protocol connection succeeds, the local system clears the Connect Retry timer, and completes initialization. It then sends an OPEN message to its peer, sets its hold timer, and changes its state to Open Sent. A hold timer value of 4 minutes is suggested.

The hold timer is 180 seconds (3 minutes) by default, or, if specified, the value in the configuration.

Frequency of route advertisement

Min Route Advertisement Interval determines the minimum interval between route advertisements to a particular destination by a BGP speaker. This rate limit applies on a per-destination basis. However, the value of Min Route Advertisement Interval is set on a per-BGP4 peer basis.

Min Route Advertisement Interval is not supported.

Min AS Origination Interval determines the minimum time that must elapse between successive advertisements of UPDATE messages that report changes within the advertising BGP speaker's own ASs.

Min AS Origination Interval is not supported.

Jitter

To minimize the likelihood that the distribution of BGP messages by a given BGP speaker will contain peaks, jitter should be applied to the timers associated with Min AS Origination Interval, Keep Alive, and Min Route Advertisement Interval.

Jitter is not applied.

Route summarization

Routes that have different MULTI_EXIT_DISC attributes must not be aggregated.

Routes that have different MULTI_EXIT_DISC attributes are aggregated.

When aggregating routes that have different NEXT_HOP attributes, the NEXT_HOP attribute of the aggregated route must identify an interface on the BGP speaker that performs the aggregation.

The NEXT_HOP attribute is not set for an aggregated route.

BGP timers

The suggested value for the Connect Retry timer is 120 seconds.

The variable (16 to 148 seconds) varies depending on the number of Connect Retry.

The suggested value for the Hold Time attribute is 90 seconds.

The default Hold Time value is 180 seconds. The value of Hold Time in the configuration is used if specified.

The suggested value for the Keep Alive timer is 30 seconds.

The default value of the Keep Alive timer is one-third of the Hold Time value. The value of Keep Alive in the configuration is used if specified.

Two optional timers (DelayOpenTimer and IdleHoldTimer) may be supported by BGP.

DelayOpenTimer and IdleHoldTimer are not supported.

RFC 5065

All BGP speakers participating as members of a confederation must recognize the AS_CONFED_SET and AS_CONFED_SEQUENCE path types.

AS_CONFED_SET is not supported. Upon receipt of a route containing AS_CONFED_SET, the Switch ignores that path type.