topic Re: Advantages of Anycast Gateway in ExtremeSwitching (VSP/Fabric Engine)

Advantages of Anycast Gateway

EF — Tue, 21 Jul 2026 11:58:32 GMT

Hi Team,

I was reading about this new feature introduced in release 9.1 that can be used to replace VRRP (which is currently my preferred option for L3 redundancy).

I have some doubts because I think I'm missing something.

What are the real advantages of Anycast Gateway? In which scenarios is it a better option than VRRP? What kind of topology is the best fit for this feature?

Thanks in advance!!!

Re: Advantages of Anycast Gateway

Ludovico — Tue, 21 Jul 2026 12:23:48 GMT

If your access switches are running SwitchEngine as FA Proxies, and you have VRRP with backup-master on the FabricEngine FA Server MLAG pair, then VRRP with Backup-Master is still perfect as you will get active-active load balancing of routed traffic on both VRRP routers (Anycast Gateway - ACGW - will also work fine).

Where ACGW shines is when the access switches are running FabricEngine. If you run VRRP here, the backup-master function becomes ineffective as the the fabric access switch will have to MAC-in-MAC encapsulate all VRRP gateway MAC destined traffic towards the real owner of the VRRP MAC i.e. only the VRRP Master router will be routing that traffic onwards, so you get no load balancing; also in certain fabric topologies the VRRP Master router might not be the nearest, so the forwarding path might be sub-optimal.

With ACGW, the fabric access switch can see if there are more ACGW gateways for the L2 I-SID (VLAN) and will deliver the traffic to the nearest gateway. If both/all gateways are equally near, then traffic from the different I-SIDs will be balances among them.

But ACGW requires some intelligence from the FabricEngine access switch which is a L2 switch. You need all FabricEngine devices to be on VOSS 9.1.0.0 or later.

Re: Advantages of Anycast Gateway

Jave — Tue, 21 Jul 2026 12:40:41 GMT

Hi @EF

With classic VRRP, a single router (the Master) handles all traffic for a given virtual IP; the other routers sit passively on standby (Backup). With Anycast IP Gateway since VOSS 9.1, every BEB (Backbone Edge Bridge) associated with the same L2 VSN configures the same gateway IP and MAC address locally, and becomes active simultaneously for that IP — there's no Master election, all nodes route at the same time. The gateway MAC uses the VRRP MAC address format with the VRID in the last byte (00:00:5e:00:01:xx), and must be identical across the different routers associated with the same L2 VSN.

Concrete advantages over VRRP

Active-active routing instead of active-passive: with VRRP, all inter-VLAN traffic is forced through the Master node; you can spread the Master role across multiple nodes, but that's only a band-aid since traffic leaving that VLAN is still limited to the throughput of a single switch. With Anycast Gateway, each BEB routes locally the traffic it receives — no bottleneck on a single node.
No traffic tromboning: without anycast, even east-west traffic between hosts on the same switch can end up having to travel to the Master switch to be routed, then back down. Anycast Gateway removes this detour since each switch routes directly.
Transparent host/VM mobility: VMs and other workloads can be moved across the fabric without changing their IP address — the new local switch simply becomes the new gateway and traffic flow is automatically optimized.
Improved resilience without convergence delay: with multiple active gateways, if one goes down, traffic is automatically redirected to another, avoiding a single point of failure — and without the failover/convergence delay inherent to VRRP (election, advertisement timers, etc.)

Regards.

Re: Advantages of Anycast Gateway

EF — Wed, 22 Jul 2026 11:33:48 GMT

Hi Jave,

Now I understand the advantages of Anycast better, but only when you have Fabric to the edge or a multi-layer Fabric deployment. When the Fabric is only in the core and the surrounding network is still legacy, I prefer VRRP with a Master/Backup configuration.

Kind regards,

Re: Advantages of Anycast Gateway

Goldy-chicken — Sat, 25 Jul 2026 01:47:05 GMT

This thread cleared up so much confusion I had about ACGW vs VRRP on our VOSS fabric we were stuck on active-passive routing for way too long without realizing there was a better option. Rolled it out on our FabricEngine access switches after upgrading to 9.1.0.0 and immediately noticed the traffic tromboning issue disappear, plus VM mobility across the fabric got way smoother finally got this sorted before our maintenance window closed around festivos febrero. Definitely worth the upgrade if you're running Fabric to the edge, though we kept VRRP on our legacy segments just like EF mentioned. Thanks for breaking down the MAC-in-MAC encapsulation part too, that was the piece I was missing!