home

Supported platforms

Vyatta NOS documentation

Learn how to install, configure, and operate Vyatta Network Operating System (Vyatta NOS), which helps to drive our virtual networking and physical platforms portfolio.

Configure symmetric routing with VRRP and BGP

An example of how to set up symmetric routing with BGP and VRRP.

In this topology, VRRP runs on the local internal LAN network. BGP runs between the ISP and the VRRP routers. The northbound traffic from the local internal LAN network routers does not use the same path as does the southbound (incoming) traffic from the ISP network routers. This mode of routing is referred to as asymmetric routing.
Note:

If you are upgrading the vRouter to the 4.0 release from any previous release, make sure that you use unique VRRP group IDs across interfaces. This is to avoid conflicts between configurations of the interfaces. Also, use only the following command and use unique VRRP group IDs for the VRRP groups that are tracked by BGP.

protocols bgp asn neighbor id interface interface-name vrrp-failover vrrp-group vrrp-group-id
VRRP groups that are not tracked do not require unique IDs within the vRouter.
Figure 1. Configuring symmetric routing for VRPP and BGP
Components of this topology
  • Vyatta01 and Vyatta02 are the two routers in the local internal LAN network that are running VRRP. Vyatta01 is the master router and Vyatta02 is the backup router.
  • CE01 and CE02 are the ISP gateway routers that are running BGP.

Both the VRRP master and backup routers, Vyatta01 and Vyatta02, are connected to an ISP gateway router, through use of BGP. This topology provides two possible outgoing and incoming paths for the traffic.

For example, the HTTP traffic passes from CE01 to the master router, Vyatta01. To make routing symmetric, the data sent from Vyatta01 must pass through CE01.

When VRRP failover occurs, the flow of northbound traffic switches to the backup router, Vyatta02 which becomes the new master router.

After the switchover, the southbound traffic coming from the ISP network to the LAN network should pass traffic through Vyatta02 to achieve symmetric routing.

BGP recognizes the multiple paths to send traffic. BGP uses the path selection algorithm to determine the best path to send traffic.

You can modify the BGP path selection process in ISP routers through the following parameters:

  • Multi-exit discriminator (MED)
  • AS PATH Length
  • BGP route map for VRRP failover

For both Vyatta01 and Vyatta02, configure as follows:

  1. Configure BGP as a client to notify VRRP state changes.
    user@system# set interfaces dataplane interface-name vrrp vrrp-group vrrp group-id notify bgp
  2. Set MED configuration for the neighbor.
    user@system# set protocols bgp asn neighbor id interface interface-name vrrp-failover vrrp-group vrrp-group-id med med-value
  3. Set prepend-as configuration for the neighbor.
    user@system# set protocols bgp asn neighbor id interface interface-name vrrp‐failover vrrp‐group vrrp‐group‐id prepend‐as as-path-string
  4. Set route-map configuration for the neighbor.
    user@system# set protocols bgp asn neighbor id interface interface-name vrrp-failover vrrp-group  vrrp-group-id route-map route-map-name