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. If you want to experience that low latency for 30 days, reach out for our free IP Transit trial.
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 |
5405:3 | 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 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 x 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 x times to ASN |
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 |
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
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 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 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 |