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Routing Configuration

Configure BGP and OSPF for subscriber route advertisement.

Overview​

The routing section configures dynamic routing protocols:

  • BGP — Border Gateway Protocol for upstream peering
  • OSPF — Open Shortest Path First for internal routing
  • Subscriber route advertisement to upstream networks
  • Integration with FRRouting

Configuration Options​

bgp​

BGP configuration section (optional).

routing:
  bgp:
    enabled: true
    asn: 64512
    neighbors:
      - address: "10.255.0.254"
        remote_as: 64500
    announce_subscriber_routes: true

BGP Options​

enabled​

Enable or disable BGP (optional).

bgp:
  enabled: true

Type: Boolean
Required: No
Default: false
Valid values: true, false

CLI:

abng# set routing bgp enabled true
asn​

Autonomous System Number (required when enabled).

bgp:
  asn: 64512

Type: Integer
Required: Yes (if BGP enabled)
Constraints: Valid ASN (1-4294967295)

Private ASN ranges:

  • 64512-65534 (16-bit)
  • 4200000000-4294967294 (32-bit)

CLI:

abng# set routing bgp asn 64512
neighbors​

BGP neighbor list (required when enabled).

bgp:
  neighbors:
    - address: "10.255.0.254"
      remote_as: 64500
Neighbor Options​

address — Neighbor IP address (required).

neighbors:
  - address: "10.255.0.254"

Type: IPv4 address
Required: Yes
Constraints: Valid IPv4 address

remote_as — Neighbor ASN (required).

neighbors:
  - remote_as: 64500

Type: Integer
Required: Yes
Constraints: Valid ASN (1-4294967295)

announce_subscriber_routes​

Advertise subscriber routes to BGP neighbors (optional).

bgp:
  announce_subscriber_routes: true

Type: Boolean
Required: No
Default: false
Valid values: true, false

Purpose: If enabled, each subscriber /32 is advertised as a BGP route.

CLI:

abng# set routing bgp announce_subscriber_routes true

ospf​

OSPF configuration section (optional).

routing:
  ospf:
    enabled: false

OSPF Options​

enabled​

Enable or disable OSPF (optional).

ospf:
  enabled: false

Type: Boolean
Required: No
Default: false
Valid values: true, false

CLI:

abng# set routing ospf enabled true

Example Configurations​

BGP Only​

routing:
  bgp:
    enabled: true
    asn: 64512
    neighbors:
      - address: "10.255.0.254"
        remote_as: 64500
    announce_subscriber_routes: true

Multiple BGP Neighbors​

routing:
  bgp:
    enabled: true
    asn: 64512
    neighbors:
      - address: "10.255.0.254"
        remote_as: 64500
      - address: "10.255.0.253"
        remote_as: 64500
    announce_subscriber_routes: true

BGP with OSPF​

routing:
  bgp:
    enabled: true
    asn: 64512
    neighbors:
      - address: "10.255.0.254"
        remote_as: 64500
    announce_subscriber_routes: true
  ospf:
    enabled: true

Configuration via CLI​

Enable BGP​

abng> configure
abng# set routing bgp enabled true
abng# set routing bgp asn 64512
abng# commit

Add BGP Neighbor​

abng# set routing bgp neighbors[0] address "10.255.0.254"
abng# set routing bgp neighbors[0] remote_as 64500
abng# commit

Enable Subscriber Route Advertisement​

abng# set routing bgp announce_subscriber_routes true
abng# commit

Enable OSPF​

abng# set routing ospf enabled true
abng# commit

Verification​

View Routing Configuration​

abng> show configuration | match "^routing:"
routing:
  bgp:
    enabled: true
    asn: 64512
    neighbors:
      - address: 10.255.0.254
        remote_as: 64500
    announce_subscriber_routes: true

View BGP Summary​

abng> show bgp summary
BGP Router ID: 10.255.0.1
Local AS: 64512

Neighbor        Remote AS  State    Uptime    Sent/Rcvd
10.255.0.254    64500      Established  14d 3h  1,247/1,245

View Routes​

abng> show routes
┌──────────────────┬──────────┬──────────────┬──────────┬──────────┐
│ Destination      │ Gateway  │ Interface    │ Protocol │ Metric   │
├──────────────────┼──────────┼──────────────┼──────────┼──────────┤
│ 203.0.113.10/32  │ —        │ ppp0         │ connected│ 0        │
│ 203.0.113.20/32  │ —        │ eth1.111.5   │ connected│ 0        │
│ 10.0.0.0/8       │ 10.255.0 │ eth2         │ bgp      │ 100      │
│ 0.0.0.0/0        │ 10.255.0 │ eth2         │ bgp      │ 100      │
└──────────────────┴──────────┴──────────────┴──────────┴──────────┘

Check FRRouting Status​

sudo systemctl status frr
sudo vtysh -c "show bgp summary"

How Routing Works​

BGP Neighbor Establishment​

  1. BNG initiates TCP connection to neighbor IP on port 179
  2. BGP OPEN message exchange
  3. Neighbor relationship established
  4. Route updates begin

Subscriber Route Advertisement​

When announce_subscriber_routes is enabled:

  1. Subscriber session established (PPPoE or DHCP)
  2. Subscriber IP assigned (e.g., 203.0.113.10)
  3. Host route created in kernel (/32 for PPPoE, /32 for DHCP)
  4. FRR picks up route via redistribute connected
  5. Route advertised to BGP neighbors
  6. Upstream network can reach subscriber directly

Route Withdrawal​

When subscriber disconnects:

  1. Session terminated
  2. Host route removed from kernel
  3. FRR withdraws route from BGP
  4. BGP neighbors receive withdrawal
  5. Route no longer reachable

Integration with FRRouting​

FRRouting is configured to:

  • Redistribute kernel routes (subscriber /32s)
  • Accept BGP routes from neighbors
  • Maintain routing table

FRR config (auto-generated):

router bgp 64512
  bgp router-id 10.255.0.1
  neighbor 10.255.0.254 remote-as 64500
  !
  address-family ipv4 unicast
    redistribute connected
    neighbor 10.255.0.254 activate
  exit-address-family

Validation Rules​

FieldValidation
bgp.enabledBoolean
bgp.asnInteger 1-4294967295
bgp.neighbors[].addressValid IPv4 address
bgp.neighbors[].remote_asInteger 1-4294967295
bgp.announce_subscriber_routesBoolean
ospf.enabledBoolean

Best Practices​

  1. ASN — Use private ASN range (64512-65534 or 4200000000+)
  2. Router ID — Use loopback IP (system.router_id)
  3. Neighbors — Configure redundant neighbors for resilience
  4. Route Advertisement — Enable for subscriber reachability
  5. Monitoring — Monitor BGP session state and route count
  6. Testing — Test with traceroute from upstream
  7. Documentation — Document ASN and neighbor relationships

Troubleshooting​

BGP Neighbor Not Establishing​

  1. Check BGP is enabled: show configuration | match bgp
  2. Check neighbor is reachable: ping 10.255.0.254
  3. Check firewall allows TCP 179
  4. Check FRR is running: sudo systemctl status frr
  5. Check FRR logs: sudo vtysh -c "show bgp neighbors"

Subscriber Routes Not Advertised​

  1. Check route advertisement is enabled: show configuration | match announce_subscriber_routes
  2. Check subscriber route exists: show routes | match 203.0.113
  3. Check FRR is advertising: sudo vtysh -c "show bgp ipv4 unicast"
  4. Check neighbor is receiving: Check upstream router's BGP table

BGP Session Flapping​

  1. Check network stability: ping -c 100 10.255.0.254
  2. Check for configuration changes
  3. Check FRR logs: sudo journalctl -u frr -f
  4. Check for resource exhaustion: free -h, df -h

Next Steps​