Applying BGP route-map to multiple BGP neighbors

Controlling traffic with BGP route mapping and service rules explained how BGP can apply different route-maps to the primary and secondary SD-WAN neighbors based on SLA health checks.

In this example, SD-WAN neighbors that are not bound to primary and secondary roles are configured.

The FortiGate has multiple SD-WAN links and has formed BGP neighbors with both ISPs.

ISP1 is used primarily for outbound traffic, and has an SD-WAN service rule using the lowest cost algorithm applied to it. When SLAs for ISP1 are not met, it will fail over to the MPLS line.

Inbound traffic is allowed by both WAN links, with each WAN advertising a community string when SLAs are met. When SLAs are not met, the WAN links advertise a different community string.

This example uses two SD-WAN links. The topology can be expanded to include more links as needed.

To configure BGP route-maps and neighbors:

1. Configure an access list for routes to be matched:

   config router access-list
       edit "net192"
           config rule
               edit 1
                   set prefix 192.168.20.0 255.255.255.0
               next
           end
       next
   end
   

2. Configure route-maps for neighbor ISP1:

   config router route-map
       edit "comm1"
           config rule
               edit 1
                   set match-ip-address "net192"
                   set set-community "64511:1"
               next
           end
       next
       edit "comm-fail1"
           config rule
               edit 1
                   set match-ip-address "net192"
                   set set-community "64511:5"
               next
           end
       next
   end
   

3. Configure route-maps for neighbor ISP2:

   config router route-map
       edit "comm2"
           config rule
               edit 1
                   set match-ip-address "net192"
                   set set-community "64522:1"
               next
           end
       next
       edit "comm-fail2"
           config rule
               edit 1
                   set match-ip-address "net192"
                   set set-community "64522:5"
               next
           end
       next
   end
   

4. Configure the BGP neighbors:

   config router bgp
       set as 64512
       set keepalive-timer 1
       set holdtime-timer 3
       config neighbor
           edit "192.168.2.1"
               set soft-reconfiguration enable
               set remote-as 64511
               set route-map-out "comm-fail1"
               set route-map-out-preferable "comm1"
           next
           edit "172.31.0.1"
               set soft-reconfiguration enable
               set remote-as 64522
               set route-map-out "comm-fail2"
               set route-map-out-preferable "comm2"
           next
       end
       config network
           edit 1
               set prefix 192.168.20.0 255.255.255.0
           next
       end
   end
   

   When SLAs are met, route-map-out-preferable is used. When SLAs are missed, route-map-out is used.

To configure SD-WAN:

1. Configure the SD-WAN members:

   config system sdwan
       set status enable
       config members
           edit 1
               set interface "port1"
               set gateway 192.168.2.1
           next
           edit 2
               set interface "MPLS"
               set cost 20
           next
       end
   end
   

2. Configure the health checks that must be met:

   config system sdwan
       config health-check
           edit "pingserver"
               set server "8.8.8.8"
               set members 2 1
               config sla
                   edit 1
                       set link-cost-factor packet-loss
                       set packetloss-threshold 2
                   next
               end
           next
       end
   end
   

3. Configure the SD-WAN neighbors and assign them a role and the health checks used to determine if the neighbor meets the SLA:

   When no role is defined, the default role, standalone, is used.

   config system sdwan
       config neighbor
           edit "192.168.2.1"
               set member 1
               set health-check "pingserver"
               set sla-id 1
           next
           edit "172.31.0.1"
               set member 2
               set health-check "pingserver"
               set sla-id 1
           next
       end
   end

Service rules

Create SD-WAN service rules to direct traffic to the SD-WAN links based on the lowest cost algorithm The same SLA health check and criteria that are used for the SD-WAN neighbor are used for this SD-WAN service rule.

When no roles are defined in the service rule, the default role, standalone, is used.

To configure the SD-WAN service rule:

config system sdwan
    config service
        edit 1
            set name "OutboundAll"
            set mode sla
            set dst "all"
            set src "all"
            config sla
                edit "pingserver"
                    set id 1
                next
            end
            set priority-members 1 2
        next
    end 
end

Verification

To verify that when both SLAs are met, port1 is selected due to its lower cost:

1. Verify the health check status:

   FortiGate-Branch # diagnose sys sdwan health-check
   Health Check(pingserver):
   Seq(2 MPLS): state(alive), packet-loss(0.000%) latency(24.709), jitter(14.996) sla_map=0x1
   Seq(1 port1): state(alive), packet-loss(0.000%) latency(28.771), jitter(14.840) sla_map=0x1
   

2. Verify SD-WAN neighbor status:

   FortiGate-Branch # diagnose sys sdwan neighbor
   Neighbor(192.168.2.1): member(1) role(standalone)
           Health-check(pingserver:1)  sla-pass selected alive
   Neighbor(172.31.0.1): member(2) role(standalone)
           Health-check(pingserver:1)  sla-pass selected alive

3. Verify service rules status:

   Because the service role is standalone, it matches both neighbors. The mode (SLA) determines that port1 is lower cost.

   FortiGate-Branch # diagnose sys sdwan service
   
   Service(1): Address Mode(IPV4) flags=0x0
     Gen(1), TOS(0x0/0x0), Protocol(0: 1->65535), Mode(sla), sla-compare-order
     Service role: standalone
     Members:
       1: Seq_num(1 port1), alive, sla(0x1), cfg_order(0), cost(0), selected
       2: Seq_num(2 MPLS), alive, sla(0x1), cfg_order(1), cost(20), selected
     Src address:
           0.0.0.0-255.255.255.255
   
     Dst address:
           0.0.0.0-255.255.255.255
   

4. Verify neighbor routers:
   1. Primary neighbor router:

      FGT-NBR1 # get router info bgp network 192.168.20.0
      BGP routing table entry for 192.168.20.0/24
      Paths: (1 available, best #1, table Default-IP-Routing-Table)
        Not advertised to any peer
        64512
          192.168.2.5 from 192.168.2.5 (192.168.122.98)
            Origin IGP metric 0, localpref 100, valid, external, best
            Community: 64511:1
            Last update: Thu Apr 30 23:59:05 2020
      

   2. Secondary neighbor router:

      FGT-NBR2 # get router info bgp network 192.168.20.0
      VRF 0 BGP routing table entry for 192.168.20.0/24
      Paths: (1 available, best #1, table Default-IP-Routing-Table)
        Not advertised to any peer
        Original VRF 0
        64512
          172.31.0.2 from 172.31.0.2 (192.168.122.98)
            Origin IGP metric 0, localpref 100, valid, external, best
            Community: 64522:1
            Last update: Fri May  1 00:11:28 2020
      

To verify that when neighbor ISP1 misses SLAs, MPLS is selected and BGP advertises a different community string for ISP1:

1. Verify the health check status:

   FortiGate-Branch # diagnose sys sdwan health-check
   Health Check(pingserver):
   Seq(2 MPLS): state(alive), packet-loss(0.000%) latency(25.637), jitter(17.820) sla_map=0x1
   Seq(1 port1): state(dead), packet-loss(16.000%) sla_map=0x0
   

2. Verify SD-WAN neighbor status:

   FortiGate-Branch # diagnose sys sdwan neighbor
   Neighbor(192.168.2.1): member(1) role(standalone)
           Health-check(pingserver:1)  sla-fail dead
   Neighbor(172.31.0.1): member(2) role(standalone)
           Health-check(pingserver:1)  sla-pass selected alive
   
   

3. Verify service rules status:

   As SLA failed for neighbor ISP1, MPLS is preferred.

   FortiGate-Branch # diagnose sys sdwan service
   
   Service(1): Address Mode(IPV4) flags=0x0
     Gen(3), TOS(0x0/0x0), Protocol(0: 1->65535), Mode(sla), sla-compare-order
     Service role: standalone
     Members:
       1: Seq_num(2 MPLS), alive, sla(0x1), cfg_order(1), cost(20), selected
       2: Seq_num(1 port1), dead, sla(0x0), cfg_order(0), cost(0)
     Src address:
           0.0.0.0-255.255.255.255
   
     Dst address:
           0.0.0.0-255.255.255.255
   
   

4. Verify neighbor routers:

   The community received on ISP1 is updated.

   1. Primary neighbor router:

      FGT-NBR1 # get router info bgp network 192.168.20.0
      BGP routing table entry for 192.168.20.0/24
      Paths: (1 available, best #1, table Default-IP-Routing-Table)
        Not advertised to any peer
        64512
          192.168.2.5 from 192.168.2.5 (192.168.122.98)
            Origin IGP metric 0, localpref 100, valid, external, best
            Community: 64511:5
            Last update: Fri May  1 00:33:26 2020
      

   2. Secondary neighbor router:

      FGT-NBR2 # get router info bgp network 192.168.20.0
      VRF 0 BGP routing table entry for 192.168.20.0/24
      Paths: (1 available, best #1, table Default-IP-Routing-Table)
        Not advertised to any peer
        Original VRF 0
        64512
          172.31.0.2 from 172.31.0.2 (192.168.122.98)
            Origin IGP metric 0, localpref 100, valid, external, best
            Community: 64522:1
            Last update: Fri May  1 00:22:42 2020