> ## Documentation Index
> Fetch the complete documentation index at: https://docs.aviatrix.com/llms.txt
> Use this file to discover all available pages before exploring further.

# AWS Transit Gateway Route Limit Test Validation

> While an AWS Transit Gateway (TGW) carries thousands of routes in the TGW route table, a TGW VPN has the same 100 route limit as the VGW VPN.

## Introduction

While an AWS Transit Gateway (TGW) carries thousands of routes in the TGW route
table, a TGW VPN has the same 100 route limit as the VGW VPN.

## Test Validation

In the following setup, we launch a Cisco CSR 1000v as the Customer Gateway and
use it to attach a VPN connection to the TGW. The TGW and the CSR also run BGP
between themselves. The detailed steps are
[here](https://docs.aws.amazon.com/vpc/latest/tgw/tgw-vpn-attachments.html).

<img src="https://mintcdn.com/aviatrix-14b37c43/0QYX2iFaLoliwUis/images/guides/connectivity/tgw/tgw-route-limit.png?fit=max&auto=format&n=0QYX2iFaLoliwUis&q=85&s=8af4537b69b56329808ae7af5f71dcc2" alt="tgw-route-limit" width="741" height="308" data-path="images/guides/connectivity/tgw/tgw-route-limit.png" />

After the VPN tunnel is created between TGW and CSR, run the following command
at CSR to verify the BGP peer connection, where 169.254.11.233 is the TGW's BGP
ID:

```
ip-10-10-0-106#show ip bgp neighbors 169.254.11.233 | include BGP state
  BGP state = Established
```

Turn on BGP debug on CSR and then configure CSR to advertise 101 routes to TGW
through BGP. CSR shows the following BGP debug messages:

```
*Dec 18 00:29:28.213: %BGP-3-NOTIFICATION: received from neighbor 169.254.11.233 6/1 (Maximum Number of Prefixes Reached) 7 bytes 00010100 000064
*Dec 18 00:29:28.213: BGP: ses global 169.254.11.233 (0x7F36A1AF6C60:1) Receive NOTIFICATION 6/1 (Maximum Number of Prefixes Reached) 7 bytes 00010100 000064
*Dec 18 00:29:28.213: %BGP-5-NBR_RESET: Neighbor 169.254.11.233 reset (BGP Notification received)
*Dec 18 00:29:28.213: BGP: ses global 169.254.11.233 (0x7F36A1AF6C60:1) Reset (BGP Notification received).
*Dec 18 00:29:28.213: BGP: 169.254.11.233 went from Established to Closing
```

The above messages show that when the TGW exceeds its route limit (100), it
sends a BGP reset message to CSR.

The BGP connection becomes idle after these messages.

```
ip-10-10-0-106#show ip bgp neighbors 169.254.11.233 | include BGP state
  BGP state = Idle
```

This test indicates that TGW has the same BGP total prefix limitation (100) as a
VGW.

## Summary

TGW VPN has a total 100 BGP prefix. In addition, a TGW cannot summarize Spoke
VPC routes.