OSPF - Dual gateway with equal default route to ISP. Possible to achieve?

[alexals]

Hello guys,

I need some help and advice on dual gateway on a network (using OSPF) with equal default route to ISP. Based on the network diagram (as attached), I have two data center; each has a single up-link to different ISP. In this case, I'm using static (default) route from core router to firewall on each data center. Both core network on DC and DR are under Area 0 of OSPF. My objective is to get those remote offices' network traffic to be load balanced on both DC and DR up-links. In other words, having 'active-active' mode for both data center. I understood that the incoming traffic from internet/ISP to reach to remote offices would be asymmetrical and this not really an issue for me. I'm more interested on having both up-link to be equally utilize and having 'active-active' network.

Kindly advice me.

Regards,

Alex

p/s: Apologize for my grammar...

[Reza Sharifi]

Hi,

The issue is that OSPF doesn't perform unequal cost load balancing. So, traffic from DC-WAN will always go out ISP1 since that is the shorted path. You can however try and manipulate the OSPF cost on DC-Core towards fw1 and make it appear as equal as DC-Interlink and DR-Core and possibly achieve load balancing that way.

Depending on the device and IOS, PFR maybe another option.

http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/pfr/configuration/xe-3s/pfr-xe-3s-book/pfr-target-disc.html

HTH

[Joseph W. Doherty]

Besides using PfR, as suggested by Reza, you could also load balance, using OSPF ECMP, by making each FW have the same OSPF cost from each core router.  This might be done with either tunnels or using VLANs, depending on the nature of your core equipment.