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Diagram:
FGT1 (Port2 172.16.1.2)-------(172.16.1.1 Port2) FGT2.
FGT1 # show router bgp
config router bgp
set as 65555
set router-id 172.16.1.2
config neighbor
edit "172.16.1.1"
set soft-reconfiguration enable
set remote-as 65444
next
end
config network
end
config redistribute "connected"
end
config redistribute "rip"
end
config redistribute "ospf"
end
config redistribute "static"
set status enable <-------
end
FGT1 # show router static
config router static
edit 1
set dst 4.4.4.4 255.255.255.255
set gateway 10.254.1.100
set device "port1"
next
end
The FortiGate modifies the NEXT_HOP attribute to its own IP address(172.16.1.2):
FGT1 # get router info bgp neighbors 172.16.1.1 advertised-routes
VRF 0 BGP table version is 1, local router ID is 172.16.1.2
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
*> 4.4.4.4/32 172.16.1.2 32768 0 ? <-/->
Total number of prefixes 1
The objective is to modify the NEXT_HOP attribute to 10.254.1.100 when FGT1 advertises the prefix 4.4.4.4 to its eBGP peer FGT2. By default, it is not possible.
FGT1 # show router bgp
config neighbor
edit "172.16.1.1"
set attribute-unchanged next-hop <-------
next
end
FGT1 # get router info bgp neighbors 172.16.1.1 advertised-routes
VRF 0 BGP table version is 1, local router ID is 172.16.1.2
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
*> 4.4.4.4/32 10.254.1.100 32768 0 ? <-/->
Total number of prefixes 1
After configuring 'set attribute-unchanged next-hop', the original next hop (10.254.1.100) was advertised to the eBGP neighbor.
The next-hop can be changed to any IP address and does not need to match the static route's gateway. For example,
even if the prefix 4.4.4.4/32 is configured with a static route pointing to 10.254.1.100, it is still possible to change the
next hop to 192.168.1.1 by configuring a route map in the outbound direction, as shown in the example below.
This is also valid when advertising the network using the network statement
FGT1 # show router bgp
config router bgp
config neighbor
edit "172.16.1.1"
set route-map-out "nexthop"
next
end
FGT1 # show router route-map
config router route-map
edit "nexthop"
config rule
edit 1
set match-ip-address "4.4.4.4"
set set-ip-nexthop 192.168.1.1
unset set-ip-prefsrc
next
end
next
end
FGT1 # show router prefix-list
config router prefix-list
edit "4.4.4.4"
config rule
edit 1
set prefix 4.4.4.4 255.255.255.255
unset ge
unset le
next
end
next
end
FGT1 # get router info bgp neighbors 172.16.1.1 advertised-routes
VRF 0 BGP table version is 1, local router ID is 172.16.1.2
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
*> 4.4.4.4/32 192.168.1.1 32768 0 ? <-/->
Total number of prefixes 1
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