Increasing NP6 offloading capacity using link aggregation groups (LAGs)

 

NP6 processors can offload sessions received by interfaces in link aggregation groups (LAGs) (IEEE 802.3ad). A LAG combines more than one physical interface into a group that functions like a single interface with a higher capacity than a single physical interface. For example, you could use a LAG if you want to offload sessions on a 30 Gbps link by adding three 10-Gbps interfaces to the same LAG.

All offloaded traffic types are supported by LAGs, including IPsec VPN traffic. Just like with normal interfaces, traffic accepted by a LAG is offloaded by the NP6 processor connected to the interfaces in the LAG that receive the traffic to be offloaded. If all interfaces in a LAG are connected to the same NP6 processor, traffic received by that LAG is offloaded by that NP6 processor. The amount of traffic that can be offloaded is limited by the capacity of the NP6 processor.

If a FortiGate has two or more NP6 processors connected by an integrated switch fabric (ISF), you can use LAGs to increase offloading by sharing the traffic load across multiple NP6 processors. You do this by adding physical interfaces connected to different NP6 processors to the same LAG.

Adding a second NP6 processor to a LAG effectively doubles the offloading capacity of the LAG. Adding a third further increases offloading. The actual increase in offloading capacity may not actually be doubled by adding a second NP6 or tripled by adding a thrid. Traffic and load conditions and other factors may limit the actual offloading result.

The increase in offloading capacity offered by LAGs and multiple NP6s is supported by the integrated switch fabric (ISF) that allows multiple NP6 processors to share session information. Most FortiGate units with multiple NP6 processors also have an ISF. However, the FortiGate-1000D does not have an ISF. On this model and others that have more than one NP6 and no ISF, if you attempt to add interfaces connected to different NP6 processors to a LAG the system displays an error message.

 

There are also a few limitations to LAG NP6 offloading support for IPsec VPN:

• IPsec VPN anti-replay protection cannot be used if IPSec is configured on a LAG that has interfaces connected to multiple NP6 processors.
• Because the encrypted traffic for one IPsec VPN tunnel has the same 5-tuple, the traffic from one tunnel can only can be balanced to one interface in a LAG. This limits the maximum throughput for one IPsec VPN tunnel in an NP6 LAG group to 10Gbps.

 

Configuring Inter-VDOM link acceleration with NP6 processors

 

FortiGate units with NP6 processors include inter-VDOM links that can be used to accelerate inter-VDOM link traffic.

• For a FortiGate unit with two NP6 processors there are two accelerated inter-VDOM links, each with two interfaces:
• npu0_vlink: npu0_vlink0 npu0_vlink1
• npu1_vlink: npu1_vlink0 npu1_vlink1

These interfaces are visible from the GUI and CLI. For a FortiGate unit with NP6 interfaces, enter the following CLI command to display the NP6-accelerated inter-VDOM links:

get system interface

…

== [ npu0_vlink0 ]

name: npu0_vlink0 mode: static ip: 0.0.0.0 0.0.0.0 status: down netbios-forward: disable type: physical sflow-sampler: disable explicit-web-proxy: disable explicit-ftp-proxy: disable mtu-override: disable wccp: disable drop-overlapped-fragment: disable drop- fragment: disable

 

== [ npu0_vlink1 ]

name: npu0_vlink1 mode: static ip: 0.0.0.0 0.0.0.0 status: down netbios-forward: disable type: physical sflow-sampler: disable explicit-web-proxy: disable explicit-ftp-proxy: disable mtu-override: disable wccp: disable drop-overlapped-fragment: disable drop- fragment: disable

 

== [ npu1_vlink0 ]

name: npu1_vlink0 mode: static ip: 0.0.0.0 0.0.0.0 status: down netbios-forward: disable type: physical sflow-sampler: disable explicit-web-proxy: disable explicit-ftp-proxy: disable mtu-override: disable wccp: disable drop-overlapped-fragment: disable drop- fragment: disable

 

== [ npu1_vlink1 ]

name: npu1_vlink1 mode: static ip: 0.0.0.0 0.0.0.0 status: down netbios-forward: disable type: physical sflow-sampler: disable explicit-web-proxy: disable explicit-ftp-proxy: disable mtu-override: disable wccp: disable drop-overlapped-fragment: disable drop- fragment: disable

…

By default the interfaces in each inter-VDOM link are assigned to the root VDOM. To use these interfaces to accelerate inter-VDOM link traffic, assign each interface in the pair to the VDOMs that you want to offload traffic between. For example, if you have added a VDOM named New-VDOM to a FortiGate unit with NP4 processors, you can go to System > Network > Interfaces and edit the npu0-vlink1 interface and set the Virtual Domain to New–VDOM. This results in an accelerated inter-VDOM link between root and New-VDOM. You can also do this from the CLI:

 

config system interface edit npu0-vlink1

set vdom New-VDOM

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