After configuring OSPF on the Tier-0 gateway, the default route (0.0.0.0/0) is advertised to the upstream physical router.

Products

• VMware NSX

Issue/Introduction

The Edge nodes are connected to dual physical upstream routers, both of which are configured with default-information originate.

Upon checking the Edge nodes' OSPF database, the 0.0.0.0/0 route is present under 'AS External Link States', advertised by one of the upstream routers.

EDGE#1(tier0_sr)> get ospf database        OSPF Router with ID (<EDGE#1>) ...                 AS External Link States Link ID         ADV Router      Age  Seq#       CkSum  Route 0.0.0.0         <ROUTER#1>   ### 0x######## 0x#### E2 0.0.0.0/0 [0x0]

In this scenario, it might be observed that the other physical upstream router is receiving this 0.0.0.0/0 route advertised back from one of the Edge nodes.

<ROUTER#2># sh ip route ospf ... 0.0.0.0/0, #####/#####: #/#     *via <TIER0_INTERFACE>, Vlan####, [###/#], ##:##:##, ospf-1, type-2

 

Environment

VMware NSX

Cause

This is expected behavior for Type-5 LSAs according to the OSPF RFC standards.

https://www.rfc-editor.org/rfc/rfc2328.html

AS-external-LSAs (LS Type = 5)             AS-external-LSAs are flooded throughout the entire AS, with the exception of stub areas (see Section 3.6).

 

Resolution

Since the NSX Edge is operating as designed, no action is required on the Edge side; the necessary configuration should be applied to the upstream physical router.