Multiple ISP load balancing

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Multiple ISP load balancing

L3 Networker

We currently have an Internet setup as shown in the image below.   ISP1 is Metro Ethernet running over a disparate fiber path at 100Mbps symmetrical bandwidth.  ISP2 is ATM over 1Gb Fiber, with a disparate fiber path and 250Mbps symmetrical bandwidth.  ISP1 and ISP1 are running BGP.  I use padding to control my preferred link, which changes depending on conditions.   ISP3 and ISP4 are business class cable modems with 105Mbps down and 10Mbps up.    The cable modems are significantly cheaper than the other connections, they are usually peered better (go figure), and they allow me to use their entire bandwidth without having to worry about usage fees.

I have a /22 on my BGP connection on ISP1 & 2, and a /32 on each of my ISP3 and ISP4 connections.   I currently have ISP3 and ISP4 plugged into Ethernet ports on my Barracuda Load Balancer.  This firewall services a separate physical open public WIFI network and performs basic NAT, DHCP, and DNS functionality.

I would like to be able to take outbound requests from network 1, behind the Palo Alto firewalls, and send the traffic through ISP3 and/or ISP4.  I don't expect to utilize BGP on these cable modems.  I expect I would NAT the outbound connection. 

It's my understanding the Palo Alto can't do this on it's own.  It can do PBF, but not load balancing.  I'm looking for suggestions on how to best accomplish outbound load balancing.  I do not expect nor do I want inbound load balancing (connections initiated from the Internet to my servers.)

internet 2013.png


L7 Applicator


Load-Balancing is not supported on PA platforms.You can play with Policy Based Forwarding to route/ classify certain traffic based on Network address/Applications etc through ISP-3/ISP-4 Outbound connection.



I suppose I could purchase two Barracuda Link Balancers, set them up HA, and then use PBF on the Palo Alto to send specific traffic to the inside vIP of the Barracudas.  Such traffic would likely need to be double NATed.  I would need to exclude B2B destinations that have IP filters in place based on our BGP network, or get static IPs on the cable modems and have those added to the IP filters.

I suppose I could connect a port from ETHERNET2 to each of the Palo Alto firewalls on a new Ethernet port, then use PBF to redirect traffic to the existing Barracuda.  Such traffic wold be double NATed.   As I've never used the police based forwarding before, I'm a bit concerned about making this change on my production firewall.

In this scenario, say I gave the Palo Alto Firewalls a address on the private inside of the Barracuda Link Balancer.  I assign it as zone WIFI and interface 1/7.   Then I create PBF rule that says if the source is (PC VLAN RANGE, Zone TRUST) and the destination is (Akamia CDN Netblock)  I forward this to egress from interface 1/7 (right?) with a next hop of, my Barracuda inside vIP.   I would create a fail-over monitor and specify an IP address to ping.  Preferably, the IP address would be a remote IP address at Akamia, not something on my LAN.  This way I can fail over if there is an upstream failure.

Do I understand correctly?  If not, what mistakes am I making?  

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