AWS Direct Connect's route prefix limit just got a 10x boost with inbound prefix controls!

Hi, it's Shii! Today I found an AWS Direct Connect update. It might look like a small detail, but it's actually great news if you're running a large network connected to AWS from on-premises, so let me walk you through it!

AWS What's New aws.amazon.com

What was announced?

According to AWS What's New, AWS Direct Connect added a new capability called "inbound prefix controls." It lets you allocate and manage inbound route-prefix allocations for your private and transit virtual interfaces (VIFs) based on what your workload actually needs.

On both dedicated and hosted connections, you can now allocate up to 1,000 prefixes each for IPv4 and IPv6 on a single VIF.

The story so far

Until now, Direct Connect private and transit VIFs could accept a maximum of 100 route prefixes advertised from your on-premises network.

If your network was large or growing, you'd hit that ceiling of 100 pretty quickly, and had to architect around it, for example by:

• summarizing (aggregating) routes to reduce the count
• segmenting routes across multiple VIFs or connections

That meant extra design work and more operational complexity just to work around the limit, which wasn't exactly fun.

What changes

With this update, you no longer have to worry about that 100-prefix wall — you can advertise your on-premises routes over Direct Connect directly. You can connect large networks as-is, without resorting to route summarization or splitting traffic across multiple VIFs or connections.

And it's not just a flat bump to 1,000 for everyone — the key part is that you allocate prefix counts per VIF. For example, on the same connection you could:

• allocate a larger share to a transit VIF that carries a lot of routes
• allocate a smaller share to a simpler private VIF

so you can right-size prefix capacity per workload. There's no additional charge either, so if you're already using an eligible connection, you can revisit your setup without worrying about cost.

Dive Deep

Under the hood, new "prefix capacity pools" are introduced at the dedicated connection level and at the Direct Connect gateway (DXGW) level. When you create or update a VIF, you specify how many prefixes to allocate to it, and that allocation draws from both the connection's pool and the pool of the DXGW it's attached to.

The pool sizes themselves aren't fixed either:

• connection pool sizes scale with the connection's speed
• link aggregation group (LAG) pool sizes scale with the number of member connections

So environments with higher-bandwidth links or larger LAGs get access to bigger prefix capacity.

You can configure prefix allocations using the AWS Direct Connect console, the CLI, or the API.

Wrap-up

Here's a quick recap:

• Inbound prefix controls raise the per-VIF limit from 100 to up to 1,000 prefixes each for IPv4 and IPv6
• Available on VIFs for both dedicated and hosted connections
• New prefix capacity pools at the dedicated connection level and the DXGW level let you tune allocation per VIF
• Connection pools scale with bandwidth, and LAG pools scale with the number of member connections
• Configurable via the console, CLI, or API, at no additional charge

If you're a network engineer who's been wrestling with route summarization or VIF splitting to work around Direct Connect's old prefix limit, this update is squarely for you!