[j-nsp] EX series - LACP flapping during ethernet storm.

[Chuck Anderson]

On Thu, Oct 20, 2011 at 10:05:58PM +0800, Mark Tinka wrote:
> We configured LAG's with LACP and our EX4200 couldn't load 
> balance any of the traffic.
> 
> While those links discuss how the box performs load sharing, 
> it isn't actually configurable at all, nor does it work. The 
> issue also affects the EX3200, but not sure about the rest 
> of the EX family.
> 
> We opened a case with JTAC and they confirmed that a 
> hardware limitation means the switch doesn't actually do any 
> kind of load balancing over LAG's. JTAC said there are some 
> internal discussions to write software to "sort of make it 
> load share", but that's not definite.
> 
> We ended swapping the switches out with Cisco's instead, and 
> got our load balancing working.

It appears to work here on 10.4R6.

Sending a large stream of traffic between host A & host B ingresses on
the first link and egresses on the second as evidenced by the pps
numbers:

ex4200> show interfaces statistics xe-0/1/0 |match pps    
  Input rate     : 112985632 bps (11250 pps)
  Output rate    : 845096 bps (602 pps)

ex4200> show interfaces statistics xe-0/1/2 |match pps    
  Input rate     : 88064 bps (137 pps)
  Output rate    : 116843816 bps (10993 pps)

Sending a large stream of traffic between host A & host C hashes to
the opposite links:

ex4200> show interfaces statistics xe-0/1/0 |match pps    
  Input rate     : 136304 bps (161 pps)
  Output rate    : 113228128 bps (10722 pps)

ex4200> show interfaces statistics xe-0/1/2 |match pps
  Input rate     : 113205336 bps (10765 pps)
  Output rate    : 4110504 bps (402 pps)

I also tested A <-> B with different TCP and UDP port numbers and the
interface selection changes, indicating that L4 fields are
successfully being taken into account in the load-balancing hash.

So at least in the basic Layer 2 bridging case, it appears to be
working.

Here is the configuration:

ex4200> show interfaces terse | match ae0 
xe-0/1/0.0              up    up   aenet    --> ae0.0
xe-0/1/2.0              up    up   aenet    --> ae0.0
ae0                     up    up  
ae0.0                   up    up   eth-switch


ex4200> show configuration interfaces xe-0/1/0 
ether-options {
    802.3ad ae0;
}

ex4200> show configuration interfaces xe-0/1/2    
ether-options {
    802.3ad ae0;
}

ex4200> show configuration interfaces ae0 
unit 0 {
    family ethernet-switching {
        port-mode trunk;
        vlan {
            members [ 1004 1005 3001 3019 1032 1176 ];
        }
    }
}