BGP Prefix List

[HS08]

I have prefix list to filter which prefix will be send to azure.

Previously ID no 4 is not exist and i can see in the advertise route only showig 10.103.0.0/16 and 172.30.30.0/24

FW01 (Internet) # get router info bgp neighbors 10.201.0.4 advertised-routes
VRF 0 BGP table version is 43362, local router ID is 10.103.103.103
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal
Origin codes: i - IGP, e - EGP, ? - incomplete

Network Next Hop Metric LocPrf Weight RouteTag Path
*> 10.103.0.0/16 10.210.0.103 100 32768 0 i <-/->
*> 172.30.30.0/24 10.210.0.103 100 32768 0 i <-/->

Total number of prefixes 2

But when i add ID number 4 above why the fgt still advertise 2 prefix and not advertise 10.105.0.0/16?

[Toshi_Esumi]

Do you have "set soft-reconfituration enable" in the neighbor configuration? If so, try "exe router clear bgp ip 10.201.0.4 soft out" a couple of times. Otherwise, you might need to reset the session (take the neighbor down and bring it back up).

Toshi 

[funkylicious]

do you have a route in RIB on the FGT for that route? if not that may be a reason why it isnt advertised.

[tayi]

check;

get router info routing-table details 10.105.0.0

or

get router info routing-table all | grep 10.105

check whether the subnet exists as 16 or 24

if no route exists for 10.105, BGP cannot advertise it

test by adding a blackhole static route;

config router static

edit 100
set dst 10.105.0.0 255.255.0.0
set blackhole enable

end

re-check;

get router info bgp neighbors 10.201.0.4 advertised-routes

[HS08 · Accepted solution]

Hi..

I just realized that prefix list will be execute from lower id to higher id. The picture i post earlier should be sort by ID. 

So after bgp to that peer cleared then only prefix 10.103.0.0/16 will be advertised.

[Toshi_Esumi]

No. They're examined from the top of the list regardless of the ID. If you go into CLI then delete the ID#1 prefix list, the GUI should show only #3, #4 and #2. Then if you go back and configure,

config router prefix-list
  edit [prefix-list_name]
    config rule
      edit 1 
        set prefix 10.103.0.0 255.255.0.0
        unset ge
        unset le
      next
    end
  next
end

the ID#1 prefix would be added to the end of the list. So now GUI would show in the order  #3, #4, #2, and #1. Then #3 would be examined first and #1 last.

Toshi