Why is BGP route not advertised?

There may be several reasons why a BGP route isn’t advertised to its eBGP neighbor in JUNOS. I was doing some tests and noticed that one of my routes 172.16.10.0 isn’t advertised to its neighbor.

Show route indicates that route is also learned via OSPF as well due to my crap topology at the moment:) and doesn’t choose it as BGP best route.

root@JGW3> show route 172.16.10.0 

inet.0: 27 destinations, 29 routes (27 active, 1 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both

172.16.10.0/24     *[OSPF/150] 00:21:41, metric 0, tag 0
                    > to 192.168.249.1 via ge-0/0/2.0
                    [BGP/170] 01:38:26, localpref 100
                      AS path: 8000 I
                    > to 192.168.250.3 via ge-0/0/0.0

inactive-path option also clearly indicates a problem with the preference.

root@JGW3> show route 172.16.10.0 inactive-path extensive

inet.0: 27 destinations, 29 routes (27 active, 1 holddown, 0 hidden)
172.16.10.0/24 (2 entries, 2 announced)
TSI:
KRT in-kernel 172.16.10.0/24 -> {192.168.249.1}
Page 0 idx 1 Type 1 val 937ce38
    Nexthop: Self
    AS path: [4000] 8000 I
    Communities:
Path 172.16.10.0 from 192.168.250.3 Vector len 4.  Val: 1
         BGP    Preference: 170/-101
                Next hop type: Router, Next hop index: 563
                Address: 0x9348520
                Next-hop reference count: 2
                Source: 192.168.250.3
                Next hop: 192.168.250.3 via ge-0/0/0.0, selected
                State: 
                Inactive reason: Route Preference
                Local AS:  4000 Peer AS:  8000
                Age: 1:34:14
                Task: BGP_8000.192.168.250.3+51757
                Announcement bits (1): 3-BGP_RT_Background
                AS path: 8000 I
                Accepted
                Localpref: 100
                Router ID: 192.168.250.3

If a route isn’t advertised, it is good to check with the detail option!

About: rtoodtoo

Worked for more than 10 years as a Network/Support Engineer and also interested in Python, Linux, Security and SD-WAN, currently living in the Netherlands and works as a Network Support Engineer. // JNCIE-SEC #223 / RHCE / PCNSE


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