Interface Cost

This feature adds multiple extensions to various objects and rules, increasing the flexibility of how SD-WAN can be set up.

The cost parameter is added for SD-WAN members, to support assigning a cost value to each interface. It can be used in SLA mode rules to select the lowest cost link from the links that otherwise satisfy the SLA. The lowest possible cost for a link is 0. If the costs are the same, the Interface preference order is used to select a link.

Interface selection based on quality now balances across all matching links that satisfy the quality SLA. Traffic can also be restricted to a specific subset of interfaces.

To configure interface cost:

config system virtual-wan-link
    config members
        edit 1
            set cost 10
        next
        edit 2
            set cost 5
        next
        ... ...
    end
end

Example

In this example:

• The SD-WAN has four members:
  • Member 1 and member 2 can satisfy the SLA and are selected as candidates.
  • Member 3 and member 4 are slower and cannot satisfy the SLA.
• The cost parameter only applies to candidates, even though the interface cost of members 3 and 4 are lower than that of members 1 and 2.

The ISP of member 1 is more expensive, so the its cost is set higher than the member 2 cost. Consequently, member 2, with the lower cost, is the first choice. If the cost parameters for all of the members were not set, or were all set to the same value, the selection would be the highest priority member that satisfies the SLA.

To configure the SD-WAN:

config system virtual-wan-link
    set status enable
    set load-balance-mode usage-based
    config members
        edit 1
            set interface "port13"
            set gateway 10.100.1.1
            set cost 10
        next
        edit 2
            set interface "port12"
            set cost 5
        next
        edit 3
            set interface "agg1"
            set gateway 172.16.203.2
            set cost 1
        next
        edit 4
            set interface "vlan200"
            set gateway 172.16.216.2
            set cost 1
        next
    end
    config health-check
        edit "ping"
            set server "10.100.2.22"
            set threshold-warning-latency 2
            set threshold-alert-latency 5
            set members 2 1 3 4
            config sla
                edit 1
                    set link-cost-factor latency
                next
                edit 2
                    set link-cost-factor latency
                    set latency-threshold 4
                next
            end
        next
    end
    config service
        edit 2
            set name "google-dns"
            set mode sla
            set src "all"
            set internet-service enable
            set internet-service-id 65539
            config sla
                edit "ping"
                    set id 2
                next
            end
            set priority-members 3 4 1 2
        next
    end
end

To check the link status and sequence:

diagnose sys virtual-wan-link health-check        <<<<<<<< check link status, pay attention to state(alive or dead) and the link quality 
    Health Check(ping):
    Seq(2): state(alive), packet-loss(0.000%) latency(0.244), jitter(0.028) sla_map=0x2
    Seq(1): state(alive), packet-loss(0.000%) latency(0.697), jitter(0.094) sla_map=0x2
    Seq(3): state(alive), packet-loss(0.000%) latency(21.835), jitter(1.159) sla_map=0x0
    Seq(4): state(alive), packet-loss(3.333%) latency(21.975), jitter(1.271) sla_map=0x0

diagnose sys virtual-wan-link service        <<<<<<<< check link sequence and pay attention to "sla(0x)" value
    Service(2): Address Mode(IPV4) flags=0x0
      TOS(0x0/0x0), Protocol(0: 1->65535), Mode(sla)
      Members:
        1: Seq_num(2), alive, sla(0x1),cfg_order(3), selected
        2: Seq_num(1), alive, sla(0x1),cfg_order(2), selected
        3: Seq_num(3), alive, sla(0x0),cfg_order(0), selected
        4: Seq_num(4), alive, sla(0x0),cfg_order(1), selected
      Internet Service: Google-DNS(65539)
      Src address: 0.0.0.0-255.255.255.255