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BGP Route Tagging

Apstra version 4.1.2 introduces a new feature where the following are tagged with BGP communities (RFC1997 - BGP Communities Attribute):

  • All routes (IPv4 and IPv6) generated within the data center fabric

  • Routes received from external generic systems

  • Routes received from remote EVPN gateways

These communities allow you to identify any BGP route within the data center fabric quickly. They'll be used for running more sophisticated route telemetry in future releases.

Introducing this new feature results in new lines of configuration on deployed network devices. These configuration changes won't impact the control or forwarding plane and thus won't be service-impacting.

BGP Route Tag Format

Each route is tagged with two communities (32-bits each) in the following format: [<system_index>:<function_id>] [<vrf_id>:<peer_id>]

Field Description Possible Range of Values

system_index

Identifies the device where the route is learned (sourced) in Apstra

A unique blueprint-wide value is generated for every leaf, spine, and super spine in the data center fabric.

0 - 19999

  • 0 - don’t care

  • 1 - 19999 usable values // block of 20.000

function_id

Identifies the route source or a function associated with it

A unique blueprint-wide value is generated for every leaf, spine, and super spine in the data center fabric.

The base for function_id is 20000. The function_id value will be 20000 + function_id. Function_id MUST be set in every tagged BGP update.

The following function_id’s have been defined:

  • EVPN DCI-GW gateway = 1

  • External router generic = 2

  • Redistributed from OSPFv2 = 3

  • Redistributed from OSPFv3 = 4

  • Redistributed from static-v4 = 5

  • Redistributed from static-v6 = 6

  • Redistributed from connected-v4 = 7

  • Redistributed from connected-v6 = 8

  • Redistributed from BGP-AFI/SAFI 1/1 = 9

  • Redistributed from BGP-AFI/SAFI 2/1 = 10

  • BGP preferred exit = 11

The following function ids are not supported in Apstra version 4.1.2

  • External router generic = 2

  • Redistributed from OSPFv2 = 3

  • Redistributed from OSPFv3 = 4

  • BGP preferred exit = 11

20000 - 20999

  • 20000 - don’t care

  • 20001 - 20999 usable values // block of 1000

vrf_id

Identifies the VRF associated with the route

A unique value is generated for every configured VRF in the blueprint. The vrf_id value in the BGP community tag will be 21000 + vrf_id.

21000 - 25999

  • 25000 - don’t care

  • 21001 - 25999 usable values // block of 5000

peer_id

Optional field. Possibly identifying the peer via which the route is learned. This field is not used in Apstra 4.1.2 and is set to a don’t care value (26000).

The peer_id is not used and is set to the default value of 26000 in Apstra version 4.1.2

26000 - 28999

  • 26000 - don’t care

  • 26001 - 28999 usable values // block of 3000