ReadyNas 2304 Bond 2nd ETH adapter | Static IP

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ejcmdq wrote:

 

The idea of using ReadyNas 2nd adapter is to fall back to other switch (main concentrator) if eth0 cannot connect to camera.

 

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Ok.  Fallback is of course a different goal from simply adding bandwidth.  

 

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ejcmdq wrote:

 

# Adaptative Loading Balancing, do you will work for us?

 

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It might - the only way to be certain is to try it (and test the failover cases).

 

The way ALB works on receive traffic is that the NAS is monitoring ARP requests, and is dynamically setting the source MAC addresses in the ARP responses to balance the connection load.  The camera making the ARP requests then will use that source MAC address in it's transmitted ethernet packets.

 

A pure layer 2 switch fabric will then route the packets from the camera to the NAS using the MAC address alone.  But a layer 2/3 switch fabric might not.  Just seeing two MAC addresses with the same IP address might confuse the fabric.

 

When this works, it isn't particularly fluid.  Whenever the sending device (camera in this case), makes an ARP request, it gets a response from the NAS - which as far as the camera is concerned binds whatever MAC address it receives to that IP address when it gets the ARP response.  It won't switch to a different MAC address unless it makes a new ARP request that gives it a different MAC address. 

 

ARP caching in the sending device (and ARP caching in the network itself) can prevent the mechanism from working in the failover case - because the new ARP request either isn't made at all, or because the new ARP request never actually reaches the NAS (because the network is ARP caching).  Another complication is that there can be multiple responses to the camera's ARP request (because the network is ARP caching), and they can have different MAC address in them.

 

So one thing to test is that both the active internet NICS in the NAS are receiving traffic from the cameras when ALB is in use.  Once that is confirmed, you can then test what happens if you disconnect the NIC that has the primary IP address.  Any active connections using that IP address will fail (so some video will be lost).  But any new connections should go the the remaining NIC.  This assumes that

1. the camera will make a fresh ARP request when the connection fails
2. ARP caching in the network itself won't prevent the fresh ARP request from reaching the NAS (or result in the camera using a netwrok-cached response).
3. any layer-3 routing in the network won't prevent the packets with the original IP address and the new MAC address from reaching the NAS. 

You'd also need to test that you get the desired behavior when you disconnect the secondary NIC.

 

BTW, TLB should have the same failover behavior as ALB - when the primary NIC is disconnected it is supposed to switch receive traffic to the second NIC.  But it won't attempt to dynamically balance the load when both NICs are working.  You might find it easier to test what happens with TLB first - if that works when you disconnect the primary NIC, restore that connection and then disconnect the secondary NIC, then ALB ought to work as well.

 

Either way, you should let the NAS take care of the IP address of the secondary NIC - you shouldn't need to set a static IP address.  The cameras would all be set to use same IP address (or the same DNS name, which binds to the same IP address).  The ARP address hack takes care of the rest.