Description

This article provides guidance in the scenario where there are routes in the OSPF database but are not in the routing table.

Symptoms

There are other routes in the OSPF database but they are not in the routing table. For example:


QFX5100> show ospf database | match 172.25.48

Extern 172.25.48.0 10.250.104.14 0x8000000a 1638 0x2 0xb062 36

Extern 172.25.48.0 10.251.200.2 0x8000279f 578 0x20 0xa32a 36

Extern 172.25.48.0 10.251.200.3 0x80001ee3 438 0x20 0x444b 36


root@QFX5100> show route 172.25.48

inet.0: 708 destinations, 1019 routes (708 active, 0 holddown, 0 hidden)

+ = Active Route, - = Last Active, * = Both

172.25.48.0/22 *[OSPF/150] 00:23:09, metric 2, tag 65500

> to 10.251.200.2 via irb.600

Solution

OSPF will only install a route in the routing table if it is considered the "best" route based on its calculated cost, meaning it will not install a route if another route to the same destination has a lower cost according to OSPF's metric calculations. 

Modification History

2025-02-21 : Article Created