Configuring on-premises routers

This document describes how to configure on-premises routers for Partner Interconnect. If you are creating a Dedicated Interconnect connection, see Configuring on-premises routers for Dedicated Interconnect.

For definitions of terms used on this page, see Cloud Interconnect key terms.

To help you solve common issues that you might encounter when using Partner Interconnect, see Troubleshooting.

When to configure your on-premises router

An on-premises router in this context means a Layer 2 or Layer 3 device that you configure to enable Partner Interconnect.

  • For Layer 2 connections, configure your on-premises router after your service provider has configured your VLAN attachments.
  • For Layer 3 connections, configuring BGP on your on-premises router is not required because the service provider configures BGP on their edge routers.

This document provides a sample topology and configuration for Layer 2 connections that you can use as a guide when configuring your on-premises router.

Topology for Layer 2 connections

In this topology, the Partner Interconnect connection or connections terminate on an on-premises router, which performs BGP peering with Cloud Router.

This sample topology uses the following Google Cloud resources:

  • The project Sample Interconnect Project
  • The network my-network
  • The region us-east1

There are two VLAN attachments, my-attachment1 and my-attachment2, which are already active and have BGP configured.

Physical topology

The following diagram shows the physical topology for Layer 2 connections. Google and your service provider set up and manage the physical connections between Google Cloud and your service provider's network.

Sample physical Layer 2 topology (click to enlarge).
Sample physical topology for Layer 2 connections (click to enlarge)

Logical topology

The following diagram shows the logical topology for Layer 2 connections.

Sample logical Layer 2 topology (click to enlarge).
Sample logical topology for Layer 2 connections (click to enlarge)

Configuring your on-premises router

This section describes how to configure Layer 2 topologies for production use. The sample configuration describes all device settings.

On-premises router settings

Based on the configuration in the sample Google Cloud project, the following table summarizes the on-premises router settings to use for the example topology.

For the sample project name, Virtual Private Cloud (VPC) network, and region used on the Google Cloud side, see the topology reference.

The hold timer and keepalive timer values allow Google to quickly transfer traffic to redundant connections in the event of an issue. Set their values as shown in the table.

Graceful restart prevents BGP sessions from packet drops and route withdrawal during Cloud Router maintenance. If your on-premises device supports BGP graceful restart, enable it and set the graceful restart and stalepath timers as shown in the table.

For more information about BGP timer settings, see the recommended values for BGP timers in the Cloud Router documentation.

Settings my-attachment1 my-attachment2
VLAN number 1010 1020
VLAN interface IP address 169.254.10.2/29 169.254.20.2/29
On-premises ASN 64500 64500
Cloud Router ASN 16550 16550
Cloud Router BGP IP address For cr1-us-east1:
169.254.10.1
For cr2-us-east1:
169.254.20.1
BGP timers Keepalive: 20 sec Keepalive: 20 sec
Hold timer: 60 sec Hold timer: 60 sec
Graceful restart: Set the graceful restart timer to a value that is appropriate for your needs. For more information, see BGP timer settings. Graceful restart: Set the graceful restart timer to a value that is appropriate for your needs.
Stalepath timer: 300 sec Stalepath timer: 300 sec
On-premises LAN subnet range 192.168.12.0/24 192.168.12.0/24

Configuration guidelines

Use the following information on your on-premises switch or router to establish a BGP session with your Cloud Router:

  • The interface IP address and peering IP address provided by your activated VLAN attachment.
  • The VLAN ID provided by your service provider.
  • A maximum transmission unit (MTU) of 1440 or 1500 bytes, depending on the MTU of your attachment and the VPC network.
  • The EBGP neighbor must have multihop configured. The recommended value for this setting is 4.

Device configuration

VLAN 1010 (Cisco) router

The following listing shows a Layer 2 sample configuration for on-premises Router1 (Cisco) on VLAN 1010:

        interface E0/0
          description connected_to_service_provider_device
          no shut

        interface E0/0.1010
          description attachment_vlan1010
          encapsulation dot1Q 1010
          ip address 169.254.10.2 255.255.255.248
          ip mtu 1440

        ip prefix-list TO_GCP seq 5 permit 192.168.12.0/24

        route-map TO_GCP_OUTBOUND permit 10
          match ip address prefix-list TO_GCP

        router bgp 64500
          bgp graceful-restart restart-time 1
           neighbor 169.254.10.1 description peering_to_cloud_router
           neighbor 169.254.10.1 remote-as 16550
           neighbor 169.254.10.1 ebgp-multihop 4
           neighbor 169.254.10.1 timers 20 60
           neighbor 169.254.10.1 update-source E0/0.1010
           neighbor 169.254.10.1 route-map TO_GCP_OUTBOUND out
      

VLAN 1020 (Juniper) router

The following listing shows a Layer 2 sample configuration for on-premises Router2 (Juniper) on VLAN 1020:

          set interfaces xe-0/0/0 description "connected_to_service_provider_device"
          set interfaces xe-0/0/0 flexible-vlan-tagging
          set interfaces xe-0/0/0 unit 1020 family inet mtu 1440
          set interfaces xe-0/0/0 unit 1020 vlan-id 1020
          set interfaces xe-0/0/0 unit 1020 family inet address 169.254.20.2/29

          set routing-options autonomous-system 64500

          set policy-options prefix-list TO_GCP 192.168.12.0/24

          set policy-options policy-statement TO_GCP_OUTBOUND term 1 from protocol direct
          set policy-options policy-statement TO_GCP_OUTBOUND term 1 from prefix-list TO_GCP
          set policy-options policy-statement TO_GCP_OUTBOUND term 1 then accept
          set policy-options policy-statement TO_GCP_OUTBOUND term 2 then reject

          set protocols bgp group config_vlan_1020 type external
          set protocols bgp group config_vlan_1020 multihop ttl 4
          set protocols bgp group config_vlan_1020 local-address 169.254.20.2
          set protocols bgp group config_vlan_1020 peer-as 16550
          set protocols bgp group config_vlan_1020 neighbor 169.254.20.1 export TO_GCP_OUTBOUND
          set protocols bgp group config_vlan_1020 neighbor 169.254.20.1 graceful-restart restart-time 1
      

Best practices

Follow these best practices to ensure effective connectivity to Google Cloud from your on-premises devices when using Cloud Interconnect 99.9% and 99.99% topologies.

Configuring devices for active/active forwarding

  • Ensure that the same MED values are exchanged across all BGP sessions.
  • Enable equal-cost multipath (ECMP) routing in your BGP configuration.
  • Enable graceful restart on your BGP sessions to minimize the impact of Cloud Router task restarts. When you connect two attachments through different edge availability domains, as described in the recommended topologies, the Cloud Router uses one task per edge availability domain. To avoid downtime, software tasks are scheduled independently.
  • If you are configuring two on-premises devices, use any routing protocol to connect both devices to each other. If you are configuring your device to use redistribution, use either IBGP or IGP.

Configuring devices for active/passive forwarding

  • To avoid asymmetric routing, make sure that higher MED values are applied on the Cloud Router side and on the on-premises device side.
  • Enable graceful restart on your BGP sessions to minimize the impact of Cloud Router task restarts. When you connect two attachments through different edge availability domains, as described in the recommended topologies, the Cloud Router uses one task per edge availability domain. To avoid downtime, software tasks are scheduled independently.
  • If you are configuring two on-premises devices, make sure that both devices have Layer 3 connectivity to each other. If you are configuring your device to use redistribution, use either IBGP or IGP.

Check that your BGP sessions are working between your on-premises network and your Google Virtual Private Cloud (VPC) network. For more information, see Viewing Cloud Router status and routes in the Cloud Router documentation.