Trunked MX WAN connection...can it be done?

[The_Roo]

I have been asked to design a Merki network with three ISP connections, connected to two MX105. What has been suggested is that each ISP is connected to a switch, ISP1 on VLAN 1000, ISP2 on VLAN 2000, and then the VLANs connected to the MXs so that each MX has its WAN 1 port connected to a VLAN 1000 Accesss port, and its WAN 2 port connected to a VLAN 2000 Accesss port. As long as the ISPs present a /29 subnet I can then have each MX on its own address and also a VIP to make failover faster. Nothing strange or unusual here, it's how things are done.

But I've got 3 ISPs....and only two physical WAN ports on each MX. the only way I can see to handle that is to trunk one of the MX WAN ports , have it configured with an SVI for one of the original two ISPs and another for the third ISP...and I can't see a way to do that.

Is it possible? any suggestions?

Thanks

Roo

[GreenMan · Accepted solution]

What you're trying to do, in terms of trunking and multiple virtual interfaces on one WAN port is not possible.

[The_Roo]

Thanks GreenMan, that confirmed what I thought.... 🙂

Roo

[PhilipDAth]

Slow down green guy, I think we can do something with some compromises.  🙂

The compromise is that only two ISP connections can be active at a time, and the third can only be used for backup.

WAN1 on MX1 and MX2 can connected to access ports on the switch in VLAN1000.

ISP2 plugs directly into WAN2 on MX1.

ISP3 plugs directly into WAN2 on MX2.

Assuming MX1 is the primary.  It will load balance across ISP1 and ISP2.  If both ISP1 and ISP2 fail, then MX1 will failover to MX2, and ISP3 will be used.

[PhilipDAth]

When I say load balance - that is optional.  You could keep ISP2 purely for failover as well.

[GreenMan]

Yeah, that would work @PhilipDAth    I was rather guilty of answering the specific question that was asked, not looking at the business requirement...   Rather unusual to want belt and braces, in terms of WAN redundancy though..?   When I come across this, it's usually cos the individual links are only available with low bandwidth, therefore active/active/active is desired which, as you say, would be a problem here.

[PhilipDAth]

I've got several customers in India, and they struggle with getting reliable ISP connections.  They fail all the time.  Some have three connections to try and cover when two of the ISPs have failed at once.