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Overview

Network Topology

BGP Policies


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Peering

Local Preference

The BGP Local Preference attribute is used to control which BGP route will be selected when multiple paths are present. The table below indicates the possible values for Local Preference of routes within the nLayer network.

Local Preference Values
Local Preference	Description
50	Depreferenced transit route
100	Default transit route
150	Depreferenced peering route
200	Default peering route
250	Depreferenced customer route
300	Default customer route
350	Preferenced customer route
400	Default internal route

BGP Communities

BGP communities are 32-bit values which are attached to a BGP route in order to carry additional information about that route. In common usage, this 32-bit value is split into two 16-bit values seperated by a colon (:), where the first half typically represents the ASN that the community "belongs to", and the second half typically represents the arbitrary data.

Announced Communities

Announced Communities are BGP communities added by nLayer to convey information about how and where the route was initially learned by our network. These communities are constructed in the following format:

4436:TCRPP

T The type of relationship that the route was learned through.
C The continent where the route was learned.
R The region of the continent where the route was learned.
PP The POP location (city code) where the route was learned.

Announced Community Values
Value	Type	Continent	Region
1	Transit	North America	North West
2	Public Peer	Europe	North
3	Private Peer	Asia	North East
4	Customer	Australia	West
5	Internal	South America	Central
6		Africa	East
7		Middle East	South West
8			South
9			South East

POP (City) Codes
Value	POP Code	City
11	IAD	Ashburn VA US
12	NYC	New York NY US
13	SJC	San Jose CA US
14	PAO	Palo Alto CA US
15	SFO	San Francisco CA US
16	ORD	Chicago IL US
17	DFW	Dallas TX US
18	LAX	Los Angeles CA US
19	EWR	Newark NJ US
20	AMS	Amsterdam NL
21	TKO	Tokyo JP
22	LHR	London UK
23	ATL	Atlanta GA US
24	PHX	Phoenix AZ US
25	MTL	Montreal QC CA
26	TOR	Toronto ON CA
27	IAH	Houston TX US
28	SEA	Seattle WA US
29	DEN	Denver CO US
30	MIA	Miami FL US

Receivable Communities

Receivable communities are BGP communities which customers can add to routes they announce to nLayer, in order to influence the propagation or attributes of the route within the nLayer network. These communities are constructed in the following format:

ASN:A0CR -or- ASN:A1PP

ASN The neighbor ASN to affect, or 4436 for all neighbor ASNs.
A The export action to perform.
C Continent Code
R Region Code
PP POP Code

ASN Values
Value	Behavior
4436	Apply to all neighboring ASNs
65001	Apply to all transits
65002	Apply to all peers
65003	Apply to all customers
#####	Apply to specified neighbor ASN

Action Codes
Community	Action
1	Prepend 4436 to route 1 time
2	Prepend 4436 to route 2 times
3	Prepend 4436 to route 3 times
4	Prepend 4436 to route 4 times
5	Set exported MED value to 0
6	Do Not Export
9	Override Do Not Export (Action 6)

Other receivable BGP community values include:

Receivable Communities
Community	Action
4436:50	Set local preference to 50
4436:100	Set local preference to 100
4436:150	Set local preference to 150
4436:200	Set local preference to 200
4436:250	Set local preference to 250
4436:300	Set local preference to 300
4436:350	Set local preference to 350
4436:666	Null route (discard) traffic
4436:998	Do not export outside current continent
4436:999	Do not export outside current region


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