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Old 09-17-2015, 03:47 PM   #1
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Registered: Sep 2012
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IPIP Encapsulation

I am trying to setup IPIP for Encapsulation vs. IPIP Tunneling.

I want to do Direct Server Return from a load balancer, where my pool members are behind a separate network (so packets must be routed to the pool). We have configured IPIP on the Load Balancer and the packets are making it to the pool member. Our pool member is currently a Ubuntu server.

I can see the packet arrive on the ethernet interface as IPIP. What I now need is for the server to unencapsulate the packet and forward it to the loopback interface that has the VIP IP on it for processing.

We do not have a "tunnel" setup between the load balancer and the VIP and hoping I do not need to.

This is what is setup:


Load Balancer (LB) public facing:
LB private facing:



Pool Member (PM) server:
PM Loopback IP:

This is what I am expecting:
Requester performs a DNS Query: -> on UDP Port 53 (DNS Query)

LB receives packet. Forwards as IPIP to -> ( ->

PM unencapsulates the packet: ->

PM forwards packet to loopback interface and the loopback handles the request.

PM replies to the DNS query directly to the client. -> UDP port 53

What is happening is:
PM receives and unencapsulates the packet.
PM replies ICMP - Unreachable protocol 4 port XX

If I define a tunnel interface on the PM, tunl0, w/ the same IP as the ethernet interface:

Then, the PM fowards the unencapsulated packet to the tunl0 interface and the packet dies there.

Three question:
1) Is it possible to use IPIP for packet encapsulation w/o having to define a tunnel?

2) If so, what might I have incorrect?

3) If not, is it enought to define the tunnel interface, or do I need more configuration on the PM?



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