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Routing Policies - Knowledgebase

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Overview

Inter.link offers a pan-european 100G network with high-quality connectivity to carriers, content providers, and internet exchanges. A three-digit number of peerings enables Inter.link to provide outstanding reach and low latency.  
 
This section of the knowledgebase explains Inter.link's routing policies, including 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.

Click the menu on the left which says 'Navigate Routing Policies' to jump to specific sections of this page.


General

  • Prefixes with RPKI validation-state invalid are dropped (exceptions are RTBH prefixes). 
  • Only prefix lengths between /8 and /24 for IPv4 and /19 and /48 for IPv6 are accepted (exceptions are RTBH prefixes). 
  • Bogon prefixes and Bogon ASNs are rejected on ingress. 
  • Strict prefix filtering based on IRR data is applied on all BGP sessions. 
  • Maximum accepted AS-Path length is 50. 
  • "Tier-1" ASNs in the as-paths from downstreams and peers are rejected. 
  • The first ASN (left most) in the AS-Path must equal the peer ASN. 
  • Peering sessions are protected with maximum prefix limits 
  • Inter.link does not use route-dampening. 
  • The Multi-exit Discriminator (MED) set by customers is honored. If unset the lowest (best) value 0 is used. 
  • Setting local preference via BGP communities is not supported (except GRACEFUL_SHUTDOWN), please use MED and/or AS-Path prepending for traffic-engineering. 
  • Prefix filters are updated once a day every (european) night.

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 Leaned 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: 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 continents1
CC Country Identifier 00 = all countries1
ZZZ City Identifier 000 = all cities1
P Peer Type Identifier  0 = all peer types1
AAA 4 Byte ASN 0 = all ASNs1

 

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
5405:1RPx:AAA scope continent (1), continent, peer type, prepend times to ASN
5405:2CCPx:AAA scope country (2), country, peer type, prepend x times to ASN
5403:3ZZZPx:AAA scope city (3), city, peer type, prepend times to ASN

 

Restrict propagation

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

 

RTBH

We support Remote Triggered Blackholing (RTBH) on a global level and for different sub-scales for customers and peers by default. This only applies for prefixes which are included in the existing ingress BGP filters. 

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 corresponding IDs are listed in the Appendix below. 

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

The prefix length for RTBH routes is no restricted. Routes with the well-known community 65535:666 are propagated to other ASNs. Assuming they support the BLACKHOLE community different blackhole route length might lead to different results: 

  • Hostroutes (IPv4 /32and IPv6 /128) will be accepted and the traffic dropped. 
  • IPv4 /24 > prefix length > /32 or IPv6  /48 > prefix length > /128 announcements might be accepted or rejected depending on the routing policy of the BGP neighbors. 
  • IPv4 prefix length > /24 or IPv6 prefix length > /48 the prefixes will probably be accepted (depending on evaluation and existence of corresponding route objects, filtering etc.). If these will result in a blackhole or will be perceived as a normal (more-specific) prefix announcement depends on the BGP policy of the recipient. 

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 scope 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
Antarctica 
3 Asia
4 Australia
5 Europe 
6 North America
7 South America

 

Country IDs

 

 Country ID (CC) Country Name
01 Australia
02 Austria
03 China
04 Czechia
05 Denmark
06 Finland
07 France
08 Germany
09 Hong Kong
10 Ireland
11 Italy
12 Japan
13 Netherlands
14 Norway
15 Portugal
16 Singapore
17 Spain
18 Sweden
19 Switzerland
21 United Kingdom of Great Britain and Northern Ireland
22 United States of America
23 Hungary

 

City IDs

 

 City ID (ZZZ) City Name
001 Amsterdam
002 Ashburn
003 Berlin
004 Copenhagen
006 Dublin
007 Dusseldorf
008 Frankfurt
009 Helsinki
010 Hong Kong
011 Lisbon
012 London
013 Los Angeles
014 Madrid
015 Miami
016 Milan
017 Munich
018 New York
019 Nuremberg
020 Oslo
021 Paris
022 Prague
023 Seattle
024 Silicon Valley
025 Singapore
026 Stockholm
027 Stuttgart
028 Sydney
029 Tokyo
030 Vienna
031 Zurich
032 Marseille
033 Budapest

 

PoP IDs

 

 PoP ID (SSS) PoP Name
001 AMS1-NL
002 AMS2-NL
003 ASH1-US
004 BER1-DE
005 BER10-DE
006 BER2-DE
007 BER3-DE
008 BER4-DE
009 BER5-DE
010 BER6-DE
011 BER7-DE
012 BER8-DE
013 BER9-DE
014 CPH1-DK
016 DUS1-DE
018 FRA1-DE
019 FRA2-DE
020 FRA3-DE
021 HEL1-FI
022 HKG1-HK
023 LIS1-PT
024 LON1-GB
025 LAX1-US
026 MAD1-ES
027 MIA1-US
028 MIL1-IT
029 MUC1-DE
030 NUE1-DE
031 NYC1-US
032 OSL1-NO
033 PAR1-FR
034 PRG1-CZ
035 SEA1-US
036 SIN1-SG
037 SJC1-US
038 STO1-SE
039 STO2-SE
040 STR1-DE
041 SYD1-AU
042 TYO1-JP
043 VIE1-AT
044 VIE2-AT
045 ZRH1-CH
046 LAB1-DE
047 MRS1-FR
048 BUD1-HU

 

Peer Type IDs

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