Description
This article describes the steps to announce multiple routes with one summary route in BGP.
Scope
All FortiGate or VDOM running in NAT mode.
Solution
Diagram:
Expectations, Requirements
This article contains the summary of the following connected networks:
* 10.162.0.0/255.255.254.0
* 10.162.2.0/255.255.254.0
* 10.162.4.0/255.255.254.0
=> As the following summarized route:
* 10.162.0.0/16
Configuration:
FGT-AS162 is the FortiGate on which is the configuration of the route summary.
FGT-AS162 (bgp) # show
config router bgp
config aggregate-address
edit 1
set prefix 10.162.0.0 255.255.0.0
set summary-only enable <- Only the aggregate route is advertised.
next
end
set as 162
config neighbor
edit 10.142.0.110
set remote-as 1
next
end
For the aggregate address to be advertised to the neighbor, at least one of its specific routes must be injected in the BGP RIB. So:
config network
edit 1
set prefix 10.162.0.0 255.255.254.0
next
edit 2
set prefix 10.162.2.0 255.255.254.0
next
edit 3
set prefix 10.162.4.0 255.255.254.0
next
end
config redistribute "connected"
end
config redistribute "rip"
end
config redistribute "ospf"
end
config redistribute "static"
end
set router-id 10.142.0.114
end
Verification:
FGT_ISP is ISP's border router.
FGT-AS162 is the FortiGate on which is the configuration to the route summary.
The following commands will be used:
# get router info bgp summary
# get router info bgp neighbors
# get router info bgp network
# get router info routing-table all
FGT-AS162:
FGT-AS162 # 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
S* 0.0.0.0/0 [10/0] via 192.168.183.254, port1
B 1.1.1.1/32 [20/0] via 10.142.0.110, port2, 01:03:29
C 10.142.0.0/23 is directly connected, port2
B 10.160.0.0/23 [20/0] via 10.142.0.110, port2, 00:02:07
B 10.162.0.0/16 [20/0] is a summary, Null, 00:12:16
C 10.162.0.0/23 is directly connected, port3
C 10.162.2.0/23 is directly connected, port5
C 10.162.4.0/23 is directly connected, port6
B 192.168.0.0/16 [20/0] via 10.142.0.110, port2, 01:03:29
B 192.168.0.0/21 [20/0] via 10.142.0.205, port2, 01:03:29
B 192.168.168.0/24 [20/0] via 10.142.0.110, port2, 01:03:29
C 192.168.182.0/23 is directly connected, port1
See above the null route in the routing table in order to prevent routing loops.
FGT-AS162 # get router info bgp network
BGP table version is 9, local router ID is 10.142.0.114
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 Path
*> 1.1.1.1/32 10.142.0.110 0 0 1 ?
*> 10.160.0.0/23 10.142.0.110 0 0 1 i
*> 10.162.0.0/16 0.0.0.0 32768 i <- This is the summary that will be sent.
s> 10.162.0.0/23 0.0.0.0 100 32768 i
s> 10.162.2.0/23 0.0.0.0 100 32768 i
s> 10.162.4.0/23 0.0.0.0 100 32768 i
*> 192.168.0.0/16 10.142.0.110 0 0 1 ?
*> 192.168.0.0/21 10.142.0.205 0 0 1 2 i
*> 192.168.168.0 10.142.0.110 0 0 1 ?
Total number of prefixes 9
See above the 's' letter that is preceding each route that is suppressed by BGP. Note that, if the 'summary-only' option is set to disable under the 'aggregate-address' configuration, those routes will not be suppressed.
On FGT_ISP:
FGT_ISP (bgp) # get router info bgp network
BGP table version is 18, local router ID is 10.142.0.110
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 Path
*> 1.1.1.1/32 192.168.183.254 32768 ?
*> 10.160.0.0/23 0.0.0.0 100 32768 i
*> 10.162.0.0/16 10.142.0.114 0 0 162 i
*> 192.168.0.0/16 192.168.183.254 32768 ?
*> 192.168.0.0/21 10.142.0.205 0 0 2 i
*> 192.168.168.0 192.168.183.254 32768 ?
Total number of prefixes 6
FGT_ISP (bgp) # 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
S 1.1.1.1/32 [10/0] via 192.168.183.254, port1
C 10.142.0.0/23 is directly connected, port6
C 10.160.0.0/23 is directly connected, port2
B 10.162.0.0/16 [20/0] via 10.142.0.114, port6, 01:04:08 <- This is the summary received on the peer.
S 192.168.0.0/16 [10/0] via 192.168.183.254, port1
B 192.168.0.0/21 [20/0] via 10.142.0.205, port6, 19:30:25
S 192.168.168.0/24 [10/0] via 192.168.183.254, port1
C 192.168.182.0/23 is directly connected, port1
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