Technical Tip: The BGP advertised and received routes have no subnet mask included
| Description | This article describes why the BGP-advertised and received routes have no subnet mask included. |
| Scope | FortiGate. |
| Solution | If the advertised and received routes have no subnet mask included, this means that the network is a classful subnet and hits the boundary. So in the below example, the 172.16.0.0 and 172.31.0.0 are using a /16 subnet mask. This is a class B subnet. The class A boundary is /8 while class C is /24.
FGT (BGP_1) # get router info bgp neighbors 1.1.1.2 advertised-routes VRF 0 BGP table version is 2, local router ID is 1.1.1.1 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 *> 172.16.0.0 1.1.1.1 100 32768 0 i <-/->
FGT (BGP_1) # get router info bgp neighbors 1.1.1.2 received-routes VRF 0 BGP table version is 4, local router ID is 1.1.1.1 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 *> 172.31.0.0 1.1.1.2 0 0 2 i <-/->
The subnet mask will be only included on the advertised and received routes that are not hitting the boundary and if the network is a classless subnet. Below is an example.
FGT (BGP_1) # get router info bgp neighbors 1.1.1.2 advertised-route VRF 0 BGP table version is 4, local router ID is 1.1.1.1 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 *> 10.1.0.0/24 1.1.1.1 100 32768 0 i <-/->
PAULO_FWF60E (BGP_1) # get router info bgp neighbors 1.1.1.2 received-routes VRF 0 BGP table version is 4, local router ID is 1.1.1.1 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 *> 10.2.0.0/24 1.1.1.2 0 0 2 i <-/-> |