AWS Network Limits and Limitations

It is good to know about the AWS network limits both for planning and troubleshooting: you can build your architecture to allow you to overcome these limits and it saves you time of troubleshooting when there is a failure or downtime in your network.

For example, an AWS VGW carries a hard limit of 100 BGP routes in total. When the BGP prefixes exceed 100, VGW randomly resets the BGP session, leading to unpredictable potential network downtime.

AWS publishes VPC limits at this link.

In addition to limits, there are limitations in functionality.

Below is a list of commonly asked limits and limitations by network engineers.

Functions Limits Comments

VPC Peering Limit per VPC

125

Default limit is 50. Constrained also by route limit of 100.

VPC Route entries in a route table

100

Default is 50. Performance impact on 100 routes.

BGP prefix total on VGW

100

Exceeding the limit results in random BGP resets.

VGW instance size scaling

Reset BGP

Trigger a BGP downtime.

DNAT function in VGW

Not available

SNAT function in VGW

Not available

NAT Gateway policies

Not available

VPN connections per VPC

10

VPN traffic initiation

From on-premises

Traffic must be initiated from on-premises to establish a VPN tunnel with VGW.

VIF per Direct Connect

50

Inter-region peering MTU size

1500 bytes

Unlike intra-region peering, there is no Jumbo Frame support, therefore inter-region performance is maxed out at 5Gbps.

Outgoing SMTP traffic on port 25

Throttled

You can send a request to lift the throttle.