If you allow me I have a quite far fetched question...

I have a fortigate 110C with a gigabit WAN port, 100mb LAN ports and a 200mb modem connected to the Fortigate. Therefore I cant have 200mb/s using the LAN ports.

Could I have two 100mb networks using two ports?

I.e 192.168.1.X using port 1 and 192.168.2.X using port 2

And each of these networks would have 100mb, theoretically.

Is this possible at all?


Both ports working as two separate networks such as 192.168.1.X and 192.168.2.X

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Aggregate interfaces Link aggregation (IEEE 802.3ad) allows you to combine two or more connected physical interfaces together to form an aggregated link. This new link has the bandwidth of all the links combined for example if we aggregate 2 links of 100mb +100mb =200mb. If a link in the group fails, traffic is automatically transferred to the remaining interfaces with the only noticeable effect being reduced bandwidth to 100 mb again in case if one link fails to accomplish your requirement aggregate 3 links of each 100mb so total bandwidth of link reaches to 300mbps . If any one of link fails. Bàndwidth will drop to 200mb which is modem bàndwidth requirement.

This is similar to redundant interfaces, with the major difference being that a redundant interface group uses only one link at a time, while an aggregate link group uses the total bandwidth of the functioning links in the group, up to eight (or more).

Some FortiGate models support the IEEE standard 802.3ad for link aggregation.

An interface can be an aggregate interface if it meets the following criteria:

It's a physical interface, not a VLAN interface or subinterface. It's not already part of an aggregate or redundant interface. It's in the same VDOM as the aggregated interface. Aggregate ports can't span multiple VDOMs. It doesn't have an IP address and isn't configured for DHCP or PPPoE. To create an aggregate interface - GUI: Go to Network > Interfaces and select Create New, then Interface. Enter the Name as Aggregate. For the Type, select 802.3ad Aggregate. If this option doesn't appear, the FortiGate doesn't support aggregate interfaces.

In the Interface Members field, click + to add interfaces. Select port 1,2 and 3 In the Addressing mode field, select Manual. Enter the IP address for the port of X.X.X.X

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Yes, you can use each LAN port for a different IP subnet - that's the main point of having multiple LAN ports.

If you want to use the full WAN bandwidth from one (or each) connected LAN, you could either bond two 100M LAN ports using LACP (Create interface -> 802.3ad Aggregate, requires an LACP-capable uplink switch) or repurpose the second 1G WAN port as LAN.

Bonding two 100M ports offers only an aggregate bandwidth of 200M, any single flow stays limited to 100M. Traffic distribution will be mostly random, so you might not get what you're looking for.

Repurposing WAN2 should work better, depending on whether there are any technical limitations on that port.

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  • To implement the bonding solution you will need an LACP-capable device behind the Forigate in order to form the logical link, which would normally be a managed switch. Unless you (OP) already have two separate networks, I'm guessing this is your best bet to utilize as much of that 200 Mbps uplink you have now. This will have the added benefit of providing some resiliency in the case one of the two ports/cables fails; if properly configured, the channel will stay up even if one of the two ethernet links fails. – Ted Quanstrom Mar 10 at 20:53

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