Multiple GRE Tunnels

Hi All,

I want to prepare two GRE tunnels to use more than 1Gbps traffic, but I cannot find any documentations for it.

Is there a good way to load balance traffic over two GRE tunnels?
I would like to know if there are any limitations or cautions.

  • Must not be per-packet load balancing
  • Must be source IP based load balancing


Zscaler supports a maximum bandwidth of 1 Gbps for each GRE tunnel if its internal IP addresses aren’t behind NAT. Zscaler uses the internal IP addresses to load balance GRE traffic over multiple servers. If the internal subnet is behind NAT, Zscaler can only support up to 250 Mbps of traffic for each tunnel. If your organization wants to forward more than 1 Gbps of traffic, Zscaler recommends configuring more GRE tunnels with different public source IP addresses. For example, if your organization forwards 2 Gbps of traffic, you can configure two primary GRE tunnels and two backup GRE tunnels. If your organization forwards 3 Gbps of traffic, you can configure three primary GRE tunnels and three backup GRE tunnels.

Hi Adoonaim, everyone.

Thank you for the information .
However, I still want to know "how can we do load balancing?
I believe there are several techniques for load balancing.


  • use Load balancer (f5, A10,etc.)
  • use policy based routing with source(client PC) IP

We shouldn’t choose packet-based forwarding way, right?
Is that the only caution point?
If there is anything else I should be aware of, please let me know.

Also, if anyone knows the best way to do this, please let me know.