Comparison
GLBP versus an EVPN anycast gateway
Both use several first-hop routers, but GLBP assigns clients to virtual forwarders through ARP while EVPN makes every attached PE the same local gateway.
Side by side
| Mechanism | GLBP | EVPN |
|---|---|---|
| Gateway identity | One virtual IP. The AVG may answer different clients with different virtual MAC addresses, one per AVF. Cisco IOS XE 17.x — Configuring GLBP §GLBP Active Virtual Gateway | Every participating PE uses the same anycast gateway IP and, in the recommended model, the same anycast MAC. IRB Interface and Its MAC and IP AddressesRFC 9135 · PROPOSED STANDARD · October 2021 |
| Who forwards | The AVF owning the virtual MAC cached by that host. A host can cross the LAN to reach a nonlocal AVF. Cisco IOS XE 17.x — Configuring GLBP §GLBP Virtual MAC Address Assignment | The PE where the host is attached routes locally, then carries the tenant packet across the overlay when the destination is remote. Data Plane - Ingress PERFC 9135 · PROPOSED STANDARD · October 2021 |
| Control mechanism | An AVG election, AVF assignments, hello/hold state, and weighting-based forwarder eligibility. Cisco IOS XE 17.x — Configuring GLBP §Information About GLBP | No per-subnet first-hop election. EVPN advertises reachability between PEs; the gateway identity is configured consistently on each IRB interface. IRB Interface and Its MAC and IP AddressesRFC 9135 · PROPOSED STANDARD · October 2021 |
| How load is shared | The AVG chooses a virtual MAC in each ARP reply using round-robin, weighted, or host-dependent assignment. Cisco IOS XE 17.x — Configuring GLBP §GLBP Benefits | Attachment determines the ingress gateway. Every leaf can route for its local hosts, so there is no ARP-based assignment across the fabric. IRB Interface and Its MAC and IP AddressesRFC 9135 · PROPOSED STANDARD · October 2021 |
| Failure behavior | A healthy member takes over the failed AVF’s virtual MAC while the AVG redirects new clients. Cached clients depend on that MAC takeover. Cisco IOS XE 17.x — Configuring GLBP §GLBP Virtual Forwarder Redundancy | A multihomed host or segment follows EVPN multihoming procedures; a singly attached host loses service with its access PE unless the attachment itself moves. Mobility ProcedureRFC 9135 · PROPOSED STANDARD · October 2021 |
What does not carry over
GLBP solves active use of several routers on one Ethernet segment. EVPN anycast gateway solves distributed routing across an overlay. The word active-active describes both outcomes but not the same mechanism.
Do not diagnose an EVPN anycast gateway by looking for an elected active router. If one leaf is forwarding only because it won an election, the design is no longer the anycast model in RFC 9135.