How to Advertise IP Pool to BGP Peer

This article describes how to advertise IP Pool to BGP Peer.

Network Diagram

Requirement

• FGT_A needs to advertise IP Pool 10.10.10.0/24 to FGT_B using BGP.
• For routes/prefixes to be advertised to BGP peers, those routes should be active on the FortiGate routing table.

Solution

Solution 1: Using Network command.

Step 1: Configure a static route for the IP Pool to Blackhole.

config router static
edit 0
set dst 10.10.10.0 255.255.255.0
set blackhole enable
next
end

Step 2: Add the IP Pool subnet to the BGP network statement.

config router bgp
config network
edit 1
set prefix 10.10.10.0 255.255.255.0
next
end
end

Result:

FGT_A # get router info bgp neighbors 192.168.254.82 advertised-routes
VRF 0 BGP table version is 4, local router ID is 192.168.254.81
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
*> 10.10.10.0/24 192.168.254.81 100 32768 0 i <-/->
*> 192.168.100.0 192.168.254.81 32768 0 ? <-/->
*> 192.168.254.0 192.168.254.81 32768 0 ? <-/->

Total number of prefixes 3


FGT_B # get router info bgp neighbors 192.168.254.81 routes
VRF 0 BGP table version is 2, local router ID is 192.168.254.82
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete

Network Next Hop Metric LocPrf Weight RouteTag Path
*> 10.10.10.0/24 192.168.254.81 0 0 0 100 i <-/1>
*> 192.168.100.0 192.168.254.81 0 0 0 100 ? <-/1>
* 192.168.254.0 192.168.254.81 0 0 0 100 ? <-/->


FGT_B # get router info routing-table all
Codes: K - kernel, C - connected, S - static, R - RIP, B - BGP
O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area
* - candidate default

Routing table for VRF=0
S* 0.0.0.0/0 [10/0] via 192.168.254.254, port1
B 10.10.10.0/24 [20/0] via 192.168.254.81 (recursive is directly connected, port1), 00:07:23
B 192.168.100.0/24 [20/0] via 192.168.254.81 (recursive is directly connected, port1), 00:20:51

Solution 2: Using redistribution.

Step 1:Configure a static route for the IP Pool to Blackhole similar to step 1 on Solution 1.

Step 2:Redistribute static routes to BGP.

config router bgp
config redistribute "static"
set status enable
end
end

Result:

FGT_A # get router info bgp neighbors 192.168.254.82 advertised-routes
VRF 0 BGP table version is 6, local router ID is 192.168.254.81
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
*> 10.10.10.0/24 192.168.254.81 32768 0 ? <-/->
*> 192.168.100.0 192.168.254.81 32768 0 ? <-/->
*> 192.168.254.0 192.168.254.81 32768 0 ? <-/->


FGT_B # get router info bgp neighbors 192.168.254.81 routes
VRF 0 BGP table version is 2, local router ID is 192.168.254.82
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete

Network Next Hop Metric LocPrf Weight RouteTag Path
*> 10.10.10.0/24 192.168.254.81 0 0 0 100 ? <-/1>
*> 192.168.100.0 192.168.254.81 0 0 0 100 ? <-/1>
* 192.168.254.0 192.168.254.81 0 0 0 100 ? <-/->

Total number of prefixes 3


FGT_B # get router info routing-table all
Codes: K - kernel, C - connected, S - static, R - RIP, B - BGP
O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area
* - candidate default

Routing table for VRF=0
S* 0.0.0.0/0 [10/0] via 192.168.254.254, port1
B 10.10.10.0/24 [20/0] via 192.168.254.81 (recursive is directly connected, port1), 00:10:18
B 192.168.100.0/24 [20/0] via 192.168.254.81 (recursive is directly connected, port1), 00:43:30