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BGP Communities

Control BGP Communities

Control BGP communities for AS203314 traffic engineering, including blackhole, propagation control, and path prepending.

Control communities allow you to dictate prefix announcements and manipulate path attributes dynamically. Attach these communities to routes you announce to AS203314 to control how we propagate them.

Traffic Engineering

These communities give you fine-grained control over route propagation and path prepending outside Hats Network.

Blackhole & Filtering

CommunityAction
203314:0:666Do not announce this route (blackhole)

Usage: Stop announcement of a prefix (e.g., during DDoS mitigation or IP address deprecation).

Note: Equivalent to standard blackhole community 65535:65281.

Propagation Control

Control which types of peers receive your routes:

CommunityAction
203314:1:0Do not send to Upstream
203314:1:1Do not send to Peering
203314:1:2Do not send to Downstream

Example Use Cases:

  • Use 203314:1:0 to prevent transit from carrying your prefix
  • Use 203314:1:1 to keep traffic limited to IX route servers
  • Use 203314:1:2 to prevent customer leakage

Geographic Restrictions

Control route propagation based on location:

CommunityAction
203314:2:1Do not send to other regions (Disable Cross Region)
203314:2:2Do not send to other PoPs (Disable Cross PoP)
203314:201:XXDo not send to Region XX

Examples:

# Keep traffic within Asia only
203314:2:1         # Disable cross-region
203314:201:300     # Exclude North America
203314:201:200     # Exclude Europe
CommunityAction
203314:202:XXXDo not send to PoP XXX

Examples:

# Exclude specific PoPs
203314:202:301     # Do not announce via Seattle
203314:202:131     # Do not announce via Tokyo
203314:202:102     # Do not announce via Hong Kong HKG2

Path Prepending

Control AS-path prepending for routes outside Hats Network:

Scope: Path prepending only affects routes announced to external peers (upstream, peering, customers)-not internal routing.

CommunityAction
203314:220:1Prepend 1x outside Hats Network
203314:220:2Prepend 2x outside Hats Network
203314:220:3Prepend 3x outside Hats Network
203314:220:4Prepend 4x outside Hats Network
203314:220:5Prepend 5x outside Hats Network

Usage: Deprioritize specific prefixes for inbound traffic engineering.

Community Decision Flow

Community Decision FlowMatch the routing goal to the right AS203314 control-community family before you announce the prefix.Start with the prefix you want AS203314 to propagateAnnounce RouteDecide whether you need local-only propagation, prepending, PoP exclusion, or peer-type filteringPick a PolicyAdd the matching 203314:* tags to the route update you send usApply CommunitiesOur edge routers ingest the route and evaluate the attached controlsAnnounce to AS203314Check route servers and looking glasses to confirm the intended propagation outcomeVerify the Effect

Usage Examples

Example 1: Local Traffic Only

Announce a prefix only within a specific region:

# Announce to Asia West only
203314:2:1         # Disable cross-region

Example 2: Deprioritize Backup Prefix

Make a backup prefix less attractive:

# Deprioritize via path prepending
203314:220:3      # Prepend 3x AS203314

Example 3: Selective Peering

Announce only to specific peer types:

# Announce to peering and customers only
203314:1:0        # Do not send to upstream

Example 4: Exclude Location

Prevent announcement via specific location:

# Exclude PoP-specific announcement
203314:202:301    # Do not send via Seattle

Example 5: Combined Control

Combine multiple communities for complex policies:

# Deprioritized, Asia-only, no upstream
203314:1:0        # No upstream
203314:2:1         # Asia only
203314:220:2      # Prepend 2x

Implementation Notes

Best Practices:

  1. Test before production: Use 203314:220:1 (1x prepend) to verify communities work
  2. Monitor impact: Check route servers and looking glasses after applying changes
  3. Document your policies: Keep track of which prefixes use which communities
  4. Use conservative prepends: 3x prepend is usually sufficient; 5x is extreme

Configuration Examples (JunOS / BIRD2)

AS203314 communities are BGP Large Communities (RFC 8092). On JunOS they are written with the large: prefix (for example large:203314:0:666). In BIRD2 they are handled via bgp_large_community with (203314, 0, 666) tuples.

Export Policy Safety Default (Strongly Recommended)

The BIRD2 examples below are export policies. The default action should be reject; to prevent route leaks if someone copy-pastes into production.
For JunOS, it's also recommended to add a final term REJECT-ALL then reject as a safety catch-all.

Example: Blackhole (203314:0:666)

set policy-options community HATS-BLACKHOLE members large:203314:0:666

set policy-options policy-statement EXPORT-TO-HATS term BLACKHOLE from route-filter 203.0.113.0/24 exact
set policy-options policy-statement EXPORT-TO-HATS term BLACKHOLE then community add HATS-BLACKHOLE
set policy-options policy-statement EXPORT-TO-HATS term BLACKHOLE then accept
set policy-options policy-statement EXPORT-TO-HATS term REJECT-ALL then reject

Example: No Upstream (203314:1:0) + Prepend 3x (203314:220:3)

set policy-options community HATS-NO-UPSTREAM members large:203314:1:0
set policy-options community HATS-PREPEND-3X members large:203314:220:3

set policy-options policy-statement EXPORT-TO-HATS term BACKUP from route-filter 203.0.113.0/24 exact
set policy-options policy-statement EXPORT-TO-HATS term BACKUP then community add [ HATS-NO-UPSTREAM HATS-PREPEND-3X ]
set policy-options policy-statement EXPORT-TO-HATS term BACKUP then accept
set policy-options policy-statement EXPORT-TO-HATS term REJECT-ALL then reject

Example: Keep in-region + Exclude a PoP (203314:2:1 + 203314:202:253)

set policy-options community HATS-NO-CROSS-REGION members large:203314:2:1
set policy-options community HATS-NO-AMS members large:203314:202:253

set policy-options policy-statement EXPORT-TO-HATS term LOCAL-ONLY from route-filter 203.0.113.0/24 exact
set policy-options policy-statement EXPORT-TO-HATS term LOCAL-ONLY then community add [ HATS-NO-CROSS-REGION HATS-NO-AMS ]
set policy-options policy-statement EXPORT-TO-HATS term LOCAL-ONLY then accept
set policy-options policy-statement EXPORT-TO-HATS term REJECT-ALL then reject

Example: Blackhole (203314:0:666)

filter export_to_hats_v4 {
  if net = 203.0.113.0/24 then {
    bgp_large_community.add((203314, 0, 666));
    accept;
  }
  reject; # Safety default
}

Example: No Upstream (203314:1:0) + Prepend 3x (203314:220:3)

filter export_to_hats_v4 {
  if net = 203.0.113.0/24 then {
    bgp_large_community.add((203314, 1, 0));
    bgp_large_community.add((203314, 220, 3));
    accept;
  }
  reject; # Safety default
}

Example: Keep in-region + Exclude a PoP (203314:2:1 + 203314:202:253)

filter export_to_hats_v4 {
  if net = 203.0.113.0/24 then {
    bgp_large_community.add((203314, 2, 1));
    bgp_large_community.add((203314, 202, 253));
    accept;
  }
  reject; # Safety default
}
  • PoP Codes - Reference for PoP numbers (XXX) in geographic restrictions
  • Region Codes - Reference for region numbers (XX) in geographic restrictions
  • Internal Communities - Communities we attach to routes we announce

Important: Control communities are applied to routes you announce to AS203314. They do not affect routes we announce to you.

Internal BGP Communities

Internal BGP communities for AS203314 indicating route origin types, PoP locations, and geographic regions.

PoP Codes

Point of Presence (PoP) codes used in AS203314 BGP communities for location-based routing across 16+ PoPs in Hong Kong, Tokyo, Singapore, Amsterdam, Frankfurt, London, Los Angeles, New York, and more.

On this page

Blackhole & Filtering
Propagation Control
Geographic Restrictions
Path Prepending
Community Decision Flow
Usage Examples
Example 1: Local Traffic Only
Example 2: Deprioritize Backup Prefix
Example 3: Selective Peering
Example 4: Exclude Location
Example 5: Combined Control
Implementation Notes
Configuration Examples (JunOS / BIRD2)
Related Information