Using BGP tags with SD-WAN rules

SD-WAN rules can use Border Gateway Protocol (BGP) learned routes as dynamic destinations.

In this example, a customer has two ISP connections, wan1 and wan2. wan1 is used primarily for direct access to internet applications, and wan2 is used primarily for traffic to the customer's data center.

The customer could create an SD-WAN rule using the data center's IP address range as the destination to force that traffic to use wan2, but the data center's IP range is not static. Instead, a BGP tag can be used.

For this example, wan2's BGP neighbor advertises the data center's network range with a community number of 30:5.

This example assumes that SD-WAN is enable on the FortiGate, wan1 and wan2 are added as SD-WAN members, and a policy and static route have been created. See SD-WAN quick start for details.

To configure BGP tags with SD-WAN rules:

1. Configure the community list:

   config router community-list
       edit "30:5"
           config rule
               edit 1
                   set action permit
                   set match "30:5"
               next
           end
       next
   end

2. Configure the route map:

   config router route-map
       edit "comm1"
           config rule
               edit 1
                   set match-community "30:5"
                   set set-route-tag 15
               next
           end
       next
   end

3. Configure BGP:

   config router bgp
       set as xxxxx
       set router-id xxxx
       config neighbor
           edit "10.100.20.2"
               set soft-reconfiguration enable
               set remote-as xxxxx
               set route-map-in "comm1"
           next
       end
   end

4. Configure a firewall policy:

   config firewall policy
       edit 1
           set name "1"
           set srcintf "dmz"
           set dstintf ""virtual-wan-link""
           set srcaddr "all"
           set dstaddr "all"
           set action accept
           set schedule "always"
           set service "ALL"
           set nat enable
       next
   end

5. Edit the SD-WAN configuration:

   config system virtual-wan-link
       set status enable
       config members
           edit 1
               set interface "wan1"
               set gateway 172.16.20.2
           next
           edit 2
               set interface "wan2"
           next
       end
       config service
           edit 1
               set name "DataCenter"
               set mode manual
               set route-tag 15
               set members 2
           next
       end
   end

Troubleshooting BGP tags with SD-WAN rules

Check the network community

Use the get router info bgp network command to check the network community:

# get router info bgp network
BGP table version is 5, local router ID is 1.1.1.1
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
*> 0.0.0.0/0 10.100.1.5 32768 0 ?
*> 1.1.1.1/32 0.0.0.0 32768 0 ?
*> 10.1.100.0/24 172.16.203.2 32768 0 ?
*> 10.100.1.0/30 0.0.0.0 32768 0 ?
*> 10.100.1.4/30 0.0.0.0 32768 0 ?
*> 10.100.1.248/29 0.0.0.0 32768 0 ?
*> 10.100.10.0/24 10.100.1.5 202 10000 15 20 e
*> 172.16.200.0/24 0.0.0.0 32768 0 ?
*> 172.16.200.200/32
                    0.0.0.0 32768 0 ?
*> 172.16.201.0/24 172.16.200.4 32768 0 ?
*> 172.16.203.0/24 0.0.0.0 32768 0 ?
*> 172.16.204.0/24 172.16.200.4 32768 0 ?
*> 172.16.205.0/24 0.0.0.0 32768 0 ?
*> 172.16.206.0/24 0.0.0.0 32768 0 ?
*> 172.16.207.1/32 0.0.0.0 32768 0 ?
*> 172.16.207.2/32 0.0.0.0 32768 0 ?
*> 172.16.212.1/32 0.0.0.0 32768 0 ?
*> 172.16.212.2/32 0.0.0.0 32768 0 ?
*> 172.17.200.200/32
                    0.0.0.0 32768 0 ?
*> 172.27.1.0/24 0.0.0.0 32768 0 ?
*> 172.27.2.0/24 0.0.0.0 32768 0 ?
*> 172.27.5.0/24 0.0.0.0 32768 0 ?
*> 172.27.6.0/24 0.0.0.0 32768 0 ?
*> 172.27.7.0/24 0.0.0.0 32768 0 ?
*> 172.27.8.0/24 0.0.0.0 32768 0 ?
*> 172.29.1.0/24 0.0.0.0 32768 0 ?
*> 172.29.2.0/24 0.0.0.0 32768 0 ?
*> 192.168.1.0 0.0.0.0 32768 0 ?

Total number of prefixes 28

# get router info bgp network 10.100.11.0
BGP routing table entry for 10.100.10.0/24
Paths: (2 available, best 1, table Default-IP-Routing-Table)
  Advertised to non peer-group peers:
   172.10.22.2
  20
    10.100.20.2 from 10.100.20.2 (6.6.6.6)
      Origin EGP metric 200, localpref 100, weight 10000, valid, external, best
      Community: 30:5 <<<<===========================
      Last update: Wen Mar 20 18:45:17 2019 

Check dynamic BGP addresses

Use the get router info route-map-address command to check dynamic BGP addresses:

# get router info route-map-address
Extend-tag: 15, interface(wan2:16)
        10.100.11.0/255.255.255.0

Check dynamic BGP addresses used in policy routes

Use the diagnose firewall proute list command to check dynamic BGP addresses used in policy routes:

# diagnose firewall proute list
list route policy info(vf=root):

id=4278779905 vwl_service=1(DataCenter) flags=0x0 tos=0x00 tos_mask=0x00 protocol=0 sport=0:65535 iif=0 dport=1-65535 oif=16
source wildcard(1): 0.0.0.0/0.0.0.0
destination wildcard(1): 10.100.11.0/255.255.255.0