BGP Communities – Knowledgebase

Inter.link offers a cross-continental 100G network with high-quality connectivity to carriers, content providers, and internet exchanges. This section explains Inter.link’s BGP communities for traffic engineering. BGP communities are provided on a best effort basis and not subject to product-specific SLAs. They are subject to change and customers and peers should check this site for updates.

BGP Origin Communities

Learned BGP routes are tagged at ingress with origin communities. These have informational value and indicate where a prefix was learned and from whom. The corresponding IDs are listed in the Appendix shown below.

Community	Purpose	Remarks
5405:P	Learned from peer type (P)	Customers, Transit, Peering or PNI
5405:1R	Learned at scope continent (1), on continent (R)
5405:2CC	Learned at scope country (2), in country (CC)
5405:3ZZZ	Learned at scope city (3), in city (ZZZ)
5405:4SSS	Learned at scope PoP (4), in PoP (SSS)

Examples The community combination 5405:3 5405:15 5405:208 5405:3003 5405:4004 attached to a route tells the following about the origin:

Community	Explanation
5405:3	Peering IXP (3)
5405:15	continent (1) Europe (5)
5405:208	country (2) Germany (08)
5405:3003	city (3) Berlin (003)
5405:4004	PoP (4) BER1-DE (004)

BGP Signalling Communities

BGP Large Communities can be used to control the behaviour of the routing service. Multiple of them can be attached to a single BGP announcement. They are stripped upon annuncement to other peers.

Abbreviation	Name	Remarks
R	Continent Identifier	0 = all continents (1)
CC	Country Identifier	00 = all countries (1)
ZZZ	City Identifier	000 = all cities (1)
P	Peer Type Identifier	0 = all peer types (1)
AAA	4 Byte ASN	0 = all ASNs (1)

¹ Only applies to AS-path prepending and propagation restriction, not to (selective) blackholing.

PATH PREPENDING COMMUNITIES

Path prepends of the ASN 5405 are supported up to three times (x = 1, 2, 3).
Prepends within a scope (e. g. country) are non-additive, the lower value is processed.
Prepends in multiples scopes (e. g. country and city) are additive.
Prepending (x = 1, 2, 3) supersedes filtering (x = 9).

Community	Purpose
5405:1 RPx:AAA	scope continent (1), continent, peer type, prepend x times to ASN
5405:2 CCPx:AAA	scope country (2), country, peer type, prepend x times to ASN
5405:3 ZZZPx:AAA	scope city (3), city, peer type, prepend x times to ASN

RESTRICT PROPAGATION

Community	Purpose
5405:1 RP9:AAA	scope continent (1), continent, peer type, do not advertise (9) to ASN
5405:2 CCP9:AAA	scope country (2), country, peer type, do not advertise (9) to ASN
5405:3 ZZZP9:AAA	scope city (3), city, do not advertise (9) to ASN

WELL-KNOWN COMMUNITIES

The following well-known communities are honoured.

Community	Purpose	Remarks
GRACEFUL_SHUTDOWN (65535:0)	lower local-pref to 1	RFC8326
BLACKHOLE (65535:666)	blackhole traffic, see RTBH	RFC7999
NO_EXPORT (65535:65281)	do not announce to any other ASN	RFC1997
NO_ADVERTISE (65535:65282)	do not announce beyond receiving PE router	RFC1997
Altering of LOCAL_PREF (5405:30)	decrease local-pref by 30	RFC1998
Altering of LOCAL_PREF (5405:50)	decrease local-pref by 50	RFC1998

REMOTE TRIGGERED BLACKHOLING (RTBH)

We support Remote Triggered Blackholing (RTBH) announcements that can activate across our global backbone, or more specific regions of it, depending on the attached community. See below for examples for choosing the right region. RTBH announcements are discarded if the prefix isn’t covered by the prefix filters configured for the peer announcing the route.

Community	Purpose	Remarks
65535:666	Global RTBH	well-known community defined in RFC7999
5405:666:1R	RTBH inside a continent (R)
5405:666:2CC	RTBH inside a country (CC)
5405:666:3ZZZ	RTBH inside a city (ZZZ)

The accepted IDs for R,CC,ZZZ can be found in the Appendix below.

If the scope of the selective blackholing matches the only origin of the route, a global blackhole is the result.

Permitted prefix length range for RTBH routes is restricted to /20 to /32 for IPv4 and /48 to /128 for IPv6. Routes with the well-known community 65535:666 are propagated to other peer/upstream ASNs as well.

For peers supporting the BLACKHOLE community, different blackhole route prefix lengths might lead to different results:

Announcements carrying Hostroutes (IPv4 /32 and IPv6 /128) are usually accepted and the traffic is dropped in the peer network.
Announcements carrying IPv4 prefixes with a length between /20 and /32 or IPv6 prefixes with a length between /48 and /128 might be accepted or rejected depending on the peer’s routing policy.

EXAMPLES

Community	Explanation
5405:1002:65550	scope continent (1), all continents (0), all peer types (0), prepend twice (2), to ASN 65550
5405:1539:0	scoper continent (1), Europe (5), all IXP peerings (3), do not announce (9), all ASNs (0)
5405:666:3003	Selective Blackhole, scope city (3), city Berlin (003)
5405:21749:0	scope country (2), Spain (17), PNI peerings (4), do not advertise (9), all (0)
5405:1039:0	scope continent (1), all continents (0), IXP peerings (3), do not announce (9), all ASNs (0)
5405:1049:0	scope continent (1), all continents (0), PNI peerings (4), do not announce (9), all ASNs (0)
5405:1039:0 5405:1049:0	The combination of these two communities mimics NOPEER community

APPENDIX

Continent IDs

Continent ID (R)	Continent Name
1	Africa
2	Antarctica
3	Asia
4	Australia
5	Europe
6	North America
7	Central America
8	South America

Country IDs

Country Name	Country ID (CC)
Australia	1
Austria	2
China	3
Czechia	4
Denmark	5
Finland	6
France	7
Germany	8
Hong Kong	9
Ireland	10
Italy	11
Japan	12
Netherlands	13
Norway	14
Portugal	15
Singapore	16
Spain	17
Sweden	18
Switzerland	19
United Arab Emirates	20
United Kingdom of Great Britain and Northern Ireland	21
United States of America	22
Hungary	23
Slovenia	24
Romania	25
Bulgaria	26
Greece	27

City IDs

City Name	City ID (ZZZ)
Amsterdam	001
Ashburn	002
Berlin	003
Copenhagen	004
Dubai	005
Dublin	006
Dusseldorf	007
Frankfurt	008
Helsinki	009
Hongkong	010
Lisbon	011
London	012
Los Angeles	013
Madrid	014
Miami	015
Milan	016
Munich	017
New York	018
Nuremberg	019
Oslo	020
Paris	021
Prague	022
Seattle	023
Silicon Valley	024
Singapore	025
Stockholm	026
Stuttgart	027
Sydney	028
Tokyo	029
Vienna	030
Zurich	031
Marseille	032
Budapest	033
Ahrensburg	034
Hamburg	035
Reston	036
Ljubljana	037
Bucharest	038
Aarhus	039
Skanderborg	040
Sofia	041
Thessaloniki	042

PoP IDs

PoP Name	PoP ID (SSS)
AMS1-NL	1
AMS2-NL	2
ASH1-US	3
BER1-DE	4
BER2-DE	6
BER3-DE	7
BER4-DE	8
CPH1-DK	14
DUB1-IE	15
DUS1-DE	16
FRA1-DE	18
FRA2-DE	19
FRA3-DE	20
LON1-GB	24
MAD1-ES	26
MIL1-IT	28
MUC1-DE	29
NUE1-DE	30
NYC1-US	31
PAR1-FR	33
PRG1-CZ	34
SEA1-US	35
STO1-SE	38
STO2-SE	39
STR1-DE	40
VIE1-AT	43
VIE2-AT	44
ZRH1-CH	45
MRS1-FR	47
BUD1-HU	48
AHR1-DE	49
HAM1-DE	50
RTV1-US	51
LJU1-SI	52
BUH1-RO	53
AAR1-DK	54
AAR2-DK	55
CPH2-DK	56
CPH3-DK	57
SKG1-DK	58
SKG2-DK	59
MUC2-DE	60
SOF1-BG	61
SKG1-GR	62
QAS1-US	69

Peer Type IDs

Peer Type ID (P)	Peer Type Name
1	Customers
2	Transit
3	Peering IXP and IXP Router Servers
4	Peering PNI