diff --git a/website/content/docs/connect/gateways/mesh-gateway/wan-federation-via-mesh-gateways.mdx b/website/content/docs/connect/gateways/mesh-gateway/wan-federation-via-mesh-gateways.mdx index 55a8194f54..1f8ca6eb79 100644 --- a/website/content/docs/connect/gateways/mesh-gateway/wan-federation-via-mesh-gateways.mdx +++ b/website/content/docs/connect/gateways/mesh-gateway/wan-federation-via-mesh-gateways.mdx @@ -184,3 +184,18 @@ expected result: - Ensure any API request that activates datacenter request forwarding. such as [`/v1/catalog/services?dc=`](/api-docs/catalog#dc-1) succeeds. + +### Upgrading the primary gateways + +Once federation is established, secondary datacenters will continuously request +updated mesh gateway addresses from the primary datacenter. Consul routes the requests + through the primary datacenter's mesh gateways. This is because +secondary datacenters cannot directly dial the primary datacenter's Consul servers. +If the primary gateways are upgraded, and their previous instances are decommissioned +before the updates are propagated, then the primary datacenter will become unreachable. + +To safely upgrade primary gateways, we recommend that you apply one of the following policies: +- Avoid decommissioning primary gateway IP addresses. This is because the [primary_gateways](/docs/agent/config/config-files#primary_gateways) addresses configured on the secondary servers act as a fallback mechanism for re-establishing connectivity to the primary. + +- Verify that addresses of the new mesh gateways in the primary were propagated +to the secondary datacenters before decommissioning the old mesh gateways in the primary.