Load Balancing with BGP in Red Hat OpenStack Platform

Red Hat OpenStack Platform leverages BGP for network performance optimization and high availability. The implementation combines FRR’s BGP capabilities with the OVN BGP agent for efficient traffic distribution.

ECMP Implementation

Equal-Cost Multi-Path (ECMP) routing is configured through FRR’s BGP daemon:

# FRR configuration for ECMP
router bgp 64999
  # Enable up to 8 equal-cost paths
  maximum-paths 8
  # Enable ECMP for iBGP peering
  maximum-paths ibgp 8

This configuration allows FRR to maintain multiple equal-cost paths in the routing table. The kernel then distributes traffic using a hash algorithm based on packet header information.

Traffic Flow and Redirection

When network traffic arrives at a node, the OVN BGP agent adds several components to redirect traffic:

  1. IP Rules: Direct traffic to specific routing tables

  2. Routes: Point to the OVS provider bridge

  3. OVS Flow Rules: Redirect traffic to the OVN overlay

These configurations work together to enable traffic to flow between external networks and the OVN overlay using RHEL kernel networking, without requiring Layer 2 connectivity between nodes.

Technical Components

The load balancing implementation includes these key components:

  1. Route Advertisement: The OVN BGP agent identifies routes to advertise: * Virtual IP addresses for OpenStack services * Provider network endpoints * Floating IP addresses

  2. Multiple BGP Peers: Configuration with multiple Top-of-Rack switches:

    # Multiple BGP peers configuration
router bgp 64999
  neighbor 192.168.1.1 remote-as 65000  # ToR Switch 1
  neighbor 192.168.2.1 remote-as 65000  # ToR Switch 2
  address-family ipv4 unicast
    network 10.0.0.0/24 # Advertise network to both peers
  exit-address-family

  3. VIP Failover: When a node fails, the OVN BGP agent: * Removes VIP advertisement from the failed node * Triggers advertisement from a healthy node * External routers automatically update routing tables

Advanced Traffic Engineering

Red Hat OpenStack Platform supports traffic engineering through BGP attributes:

  1. AS Path Prepending: Influence path selection:

    # Make a path less preferred
router bgp 64999
  address-family ipv4 unicast
    neighbor 192.168.1.1 route-map PREPEND out
  exit-address-family

route-map PREPEND permit 10
  set as-path prepend 64999 64999

  2. BGP Communities: Tag routes for selective routing:

     # Set community values
 router bgp 64999
   address-family ipv4 unicast
     network 10.0.0.0/24 route-map SET-COMMUNITY
exit-address-family
    route-map SET-COMMUNITY permit 10

    set community 64999:100

  3. BFD Integration: Fast failure detection:

    # Enable BFD
router bgp 64999
  neighbor 192.168.1.1 bfd
  neighbor 192.168.2.1 bfd

Monitoring

Commands to monitor BGP load balancing status:

# Check BGP peers status
$ sudo podman exec -it frr vtysh -c 'show bgp summary'

# View active routes and next-hops
$ sudo podman exec -it frr vtysh -c 'show ip bgp'

# Verify ECMP routes
$ sudo podman exec -it frr vtysh -c 'show ip route'

These commands help administrators verify that load balancing is functioning correctly and troubleshoot any issues that might arise.