Inter-site Redundancy Scenarios

This section describes that how the inter-site redundancy deployment works in the different scenarios:

In a scenario with two sites and both operational, each site have one primary/active GR (Gateway Router) instance. The endpoint configured on each site carries traffic corresponding to its active instance. It is possible that the Aggregation Router (ARG) may not be directly connected to the sites, and there could be multiple autonomous systems between the ARG and sites. The ARG router is responsible for the convergence of the routes from both sites.

Following are the various scenarios for the site redundancy:

  • During sunny weather conditions, Site A advertises the best route for GR1 and a less favorable route for the endpoint associated with GR2.

    On the ARG, following are the routes:

    • Routes from Site A

      • 209.165.200.225 AS-Path 65000 65000 65000 65000

      • 209.165.200.235 AS-Path 65000 65000 65000 65000 65000 65000 65000

    • Routes from Site B

      • 209.165.200.225 AS-Path 64000 64000 64000 64000 64000 64000

      • 209.165.200.235 AS-Path 64000 64000 64000 64000

    • Best Path:

      • Site-A 209.165.200.225 AS-path 65000 65000 65000 65000

      • Site -B 209.165.200.235 AS-path 64000 64000 64000 64000

Now if the Site A goes down:

The BGP session on the ARG routers goes down after the BGP convergence time, resulting in the withdrawal of routes learned from Site A. The current state of routes at ARG is as follows.

  • Routes from Site B:

    • 209.165.200.225 AS-Path 64000 64000 64000 64000 64000 64000 64000

    • 209.165.200.235 AS-Path 64000 64000 64000 64000

    Now the traffic for both the endpoints 209.165.200.225 and 209.165.200.225 is being sent towards site B.

  • The traffic monitoring feature at site B has identified traffic for the IP address 209.165.200.225. Once the packet threshold for this IP address is exceeded, the GeoReplication pod triggers the transition of the GR-1 instance from standby mode to active mode.

  • After the Geo-pod notifies the BGPSpeaker-pod of the transition of GR1 to the primary instance, the BGPSpeaker-pod readvertises the routes for the GR1 endpoint using the most favorable routing path.

  • Now the routes in the ARG are updated with following information:

    • Routes from site B:

      • 209.165.200.225 AS-Path 64000 64000 64000 64000

      • 209.165.200.235 AS-Path 64000 64000 64000 64000