Interdomain Routing · RFC 4271

Border Gateway Protocol

The interdomain routing protocol of the internet, and the control plane of modern DC fabrics. OcNOS implements BGP-4 (RFC 4271) with the full extension set required for SP transit, IXP peering, and leaf-spine DC underlay.

BGP Peering Topology

Two autonomous systems exchanging routes via eBGP, with the local AS running iBGP through a Route Reflector to scale full-mesh peering.

BGP topology: eBGP peering between AS 65001 and AS 65002, with two PEs running iBGP through a Route Reflector
BGP: eBGP peering between two ASes, with iBGP and a Route Reflector inside AS 65001.

BGP in Service Provider and DC Contexts

BGP-4 (RFC 4271) is a path-vector protocol that exchanges reachability information between autonomous systems. Its policy model, including route maps, community tagging, and AS-path filtering, gives operators precise control over traffic engineering across AS boundaries. The BGP multi-protocol extensions (RFC 4760) allow the same session to carry multiple address families: IPv4, IPv6, VPN, EVPN, SR-TE, and more.

In the data center, BGP has replaced OSPF and IS-IS as the de facto underlay in large-scale leaf-spine designs. RFC 7938 (Use of BGP for Routing in Large-Scale Data Centers) documents this shift: eBGP unnumbered sessions between leaf and spine, private ASNs per-device, and ADD-PATH for ECMP load distribution. OcNOS supports all three RFC 7938 design patterns.

BGP-LU (RFC 3107) distributes MPLS labels with BGP prefixes, enabling inter-AS MPLS LSP stitching without LDP. This is the foundation for BGP-signaled L3VPN Option C deployments across AS boundaries without exchanging full VPN routing tables at the border.

BGP FlowSpec

BGP FlowSpec (RFC 5575, RFC 8955) distributes traffic flow specifications as BGP routes. Each FlowSpec route matches a 5-tuple (or extended match criteria) and carries a REDIRECT or RATE-LIMIT action. This enables distributed DDoS mitigation at the network edge: a controller pushes a FlowSpec prefix to all PE routers simultaneously, black-holing or rate-limiting attack traffic without manual per-device configuration.

OcNOS Implementation

BGP-4 Base

RFC 4271 full compliance. 4-byte ASN (RFC 6793). MD5 TCP authentication (RFC 2385). Graceful Restart (RFC 4724). BGP NOTIFICATION reason codes.

Route Reflector

RR cluster support. Multiple RR clients per cluster. ORIGINATOR_ID and CLUSTER_LIST loop prevention. Confederation support (RFC 5065). On-demand RR for scaled deployments.

ADD-PATH / ECMP

RFC 7911 ADD-PATH. Up to 64-way ECMP in hardware. Per-prefix multipath relaxed comparison. Consistent next-hop for inter-cluster load sharing.

BGP-LU

RFC 3107 labeled unicast. Per-prefix label allocation. Inter-AS MPLS LSP stitching without LDP. Compatible with SR-MPLS co-existence.

FlowSpec

RFC 5575 / RFC 8955. IPv4 and IPv6 flow types. REDIRECT_VRF, REDIRECT_NH, RATE-LIMIT actions. Integration with ACL hardware for line-rate enforcement.

EVPN Address Family

L2VPN EVPN AFI/SAFI (25/70). Type-2, Type-3, Type-4, Type-5 routes. RT import/export policy. eBGP EVPN for DC leaf-spine (RFC 7432 §11).

BFD Fast Drain

BFD for BGP (RFC 5882). Sub-second peer failure detection. Per-session BFD discriminator. Integrated with ECMP next-hop withdrawal on BFD down.

Policy & Filtering

Route maps, prefix-lists, community-lists. Large community (RFC 8092). Extended community for VPN RT. AS-path regex filtering. NEXT_HOP rewrite and local preference manipulation.

OcNOS-Validated Hardware

For reference only. The platforms below are a representative subset of BGP-validated hardware. The complete, current list of qualified platforms, with ASIC, port density, and version coverage, is maintained in the OcNOS Hardware Compatibility List.

UfiSpace S9600-32X
Qumran2c · 32×100G
UfiSpace S9610-36D
Jericho2c+ · 36×400G
Edgecore AS7946-74XKSB
Qumran2c · 64×25G + 10×100G
UfiSpace S9510-28DC
Qumran2a · 24×25G + 2×100G + 2×400G
Edgecore AS7326-56X
Trident 3 X7 · 48×25G + 8×100G
Edgecore AS9726-32DB
Trident 4 · 32×400G
Edgecore AS9736-64D
Tomahawk 4 · 64×400G
Edgecore AIS800-64D
Tomahawk 5 · 64×800G
See all platforms in Qualified Hardware → BGP Feature Matrix →

Related Technologies & Solutions

SR-MPLS → SRv6 → EVPN-VXLAN → EVPN multi-homing → RoCEv2 → AI fabric topologies → 400G ZR/ZR+ DCI → SP Networks Solution → DC Fabric Solution → AI Fabric Solution → DDoS Protection Solution → OcNOS Feature Matrix →

Compare BGP support across all OcNOS-validated platforms

Open Feature Matrix →
FAQ

Frequently asked questions

What is BGP used for?
BGP exchanges routing reachability between autonomous systems, making it the interdomain routing protocol of the internet. It is also widely used as the underlay control plane in large-scale leaf-spine data center fabrics, where eBGP runs between leaf and spine switches.
Why is BGP used in data center fabrics instead of OSPF or IS-IS?
RFC 7938 documents BGP as the de facto underlay for large leaf-spine designs. It scales predictably with eBGP unnumbered sessions between leaf and spine, a private ASN per device, and ADD-PATH for ECMP load distribution. OcNOS supports all three RFC 7938 patterns.
What is BGP FlowSpec?
BGP FlowSpec (RFC 5575, RFC 8955) distributes traffic flow specifications as BGP routes, each matching a 5-tuple and carrying a redirect or rate-limit action. It enables distributed DDoS mitigation: a controller pushes one FlowSpec route and every edge router enforces it at once.
What is BGP-LU?
BGP-LU (BGP labeled unicast, RFC 3107) distributes MPLS labels alongside BGP prefixes, enabling inter-AS MPLS LSP stitching without LDP. It is the foundation for BGP-signaled L3VPN Option C deployments across AS boundaries. OcNOS supports BGP-LU with SR-MPLS co-existence.
Which hardware runs OcNOS BGP?
OcNOS BGP is supported on a range of open routers and switches from vendors such as UfiSpace and Edgecore, spanning Broadcom Qumran, Jericho2, Trident, and Tomahawk silicon. The current qualified list is maintained in the OcNOS Hardware Compatibility List.
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