---
name: transit-gateway-conn-basics
title: Connectivity issue basics
description: There are several simple issues that might be causing your connectivity issues. Verify the following tasks to eliminate them as problems.
last-updated: 2026-08-05
---

> ## Documentation Index
> The table of contents for this documentation set is at https://cloud.ibm.com/docs/transit-gateway?format=markdown
> The index for all IBM Cloud docs is at: https://cloud.ibm.com/docs/llms.txt
> Use these files to discover more information as needed.

# Connectivity issue basics
{: #connectivity-basics}

There are several simple issues that might be causing your connectivity issues. Verify the following tasks to eliminate them as problems.
{: shortdesc}

## Checking your permissions
{: #confirm-configuration}

If you are encountering resource issues on the provisioning page, make sure you have the correct [IAM permissions](https://cloud.ibm.com/docs/transit-gateway?topic=transit-gateway-iam&format=markdown) to use IBM Cloud Transit Gateway and IBM Cloud VPC for the connections you are attempting to make.

If you can't successfully provision a transit gateway, your account administrator might have disabled certain users' visibility to the [IBM Cloud catalog](https://cloud.ibm.com/docs/account?topic=account-restrict-by-user&format=markdown).
{: tip}

## Using supported locations
{: #confirm-locations}

If you are not able to establish connectivity between networks interconnected by a transit gateway, ensure that your networks are located in one of the [Transit gateway supported locations](https://cloud.ibm.com/docs/transit-gateway?topic=transit-gateway-tg-locations&format=markdown). You cannot establish connectivity to a resource in an unsupported location.

## Working with security groups
{: #working-with-security-groups}

[Security groups](https://cloud.ibm.com/docs/vpc?topic=vpc-using-security-groups&format=markdown#using-security-groups) exist at the virtual server instance level. Ensure that you allow the protocol you are using to egress from the originator and ingress at the target.

## Working with Access Control Lists
{: #acls}

Network Access Control Lists [ACLs](https://cloud.ibm.com/docs/vpc?topic=vpc-using-acls&format=markdown#using-acls) are applied at the VPC level. By default, they allow all inbound and outbound traffic. Check if you have changed this default.

## Interconnecting VPCs
{: #interconnect-vpcs}

You can create a single transit gateway or multiple transit gateways to interconnect more than one IBM Cloud VPCs. You can also connect your IBM Cloud classic infrastructure to a transit gateway to provide seamless communication with classic infrastructure resources. For more information, refer to [Interconnecting VPCs](https://cloud.ibm.com/docs/vpc?topic=vpc-interconnectivity&interface=cli&format=markdown#interconnecting-vpcs).