Technical Tip: Redundant route not install in the routing-table from second ISP via eBGP dynamic routing

When FortiGate has two ISP BGP peering that are advertising the default route or the same route, FortiGate may not install the routes in the routing-table. This would be an expected behavior of BGP protocol to install one route only as its best route.

In this example, BGP peering is with 10.193.4.152 and 10.201.4.152 which both are advertising a default route and 172.21.0.0/20 subnet.

juara-kvm89 # get router info bgp summary

VRF 0 BGP router identifier 10.1.1.1, local AS number 65510
BGP table version is 2
3 BGP AS-PATH entries
0 BGP community entries

Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd
10.193.4.152 4 65520 33 60 2 0 0 00:00:36 2
10.201.4.152 4 65530 16 21 2 0 0 00:00:33 2

juara-kvm89 # get router info bgp neighbors 10.193.4.152 received-routes
VRF 0 BGP table version is 2, local router ID is 10.1.1.1
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
*> 0.0.0.0/0 10.193.4.152 0 0 65520 ? <-/->
*> 172.21.0.0/20 10.193.4.152 0 0 65520 ? <-/->

Total number of prefixes 2

juara-kvm89 # get router info bgp neighbors 10.201.4.152 received-routes
VRF 0 BGP table version is 2, local router ID is 10.1.1.1
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
*> 0.0.0.0/0 10.201.4.152 0 0 65530 ? <-/->
*> 172.21.0.0/20 10.201.4.152 0 0 65530 ? <-/->

juara-kvm89 # get router info routing-table bgp
Routing table for VRF=0
B* 0.0.0.0/0 [20/0] via 10.193.4.152 (recursive is directly connected, port9), 00:03:49, [1/0]

B 172.21.0.0/20 [20/0] via 10.193.4.152 (recursive is directly connected, port9), 00:03:49, [1/0]

From the output of the routing-table, BGP is only installed from one peer only. To install both routes from both peers, the 'ebgp-multipath' would need to be enabled.

config router bgp
    set ebgp-multipath enable  << 
end

Below is the updated routing-table showing both routes from both peers.

juara-kvm89 # get router info routing-table bgp
Routing table for VRF=0
B* 0.0.0.0/0 [20/0] via 10.201.4.152 (recursive is directly connected, port10), 00:00:46, [1/0]
[20/0] via 10.193.4.152 (recursive is directly connected, port9), 00:00:46, [1/0]
B 172.21.0.0/20 [20/0] via 10.201.4.152 (recursive is directly connected, port10), 00:00:46, [1/0]
[20/0] via 10.193.4.152 (recursive is directly connected, port9), 00:00:46, [1/0]