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

[Mark Tinka]

On Friday, October 21, 2011 12:00:47 AM Alexandre Snarskii 
wrote:

> Well, there are scenarios when load-balancing will not
> happen (for example, if LAG carries point-to-point link
> between routers, and traffic is MPLS-encapsulated), but
> this is expected behaviour (S/D mac's are always the
> same in this case, and that's the only option for non-ip
> traffic on EX series).

That was my initial deduction (you're right, our traffic is 
MPLS-encapsulated on egress) during the maintenance window, 
but then remembered that before our Cisco 6500's could 
specifically add MPLS labels to the hash algorithm, I could 
load balance MPLS traffic with no issue.

Below is the algorithm on the Cisco that replaced the 
EX4200. Notice it doesn't support MPLS labels for hashing:

test at lab#sh etherchannel load-balance 
EtherChannel Load-Balancing Configuration:
        src-dst-ip

EtherChannel Load-Balancing Addresses Used Per-Protocol:
Non-IP: Disabled
  IPv4: Source XOR Destination IP address
  IPv6: Source XOR Destination IP address

test at lab#


Now look at the 6500 which does (and also supports load 
balancing of MPLS traffic):

test at lab#sh etherchannel load-balance 
EtherChannel Load-Balancing Configuration:
        src-dst-ip
        mpls label-ip

EtherChannel Load-Balancing Addresses Used Per-Protocol:
Non-IP: Source XOR Destination MAC address
  IPv4: Source XOR Destination IP address
  IPv6: Source XOR Destination IP address
  MPLS: Label or IP
test at lab#


So I assumed that since the Cisco could look deeper into the 
frame and extract IP information on which to hash, that the 
EX4200 could do it.

Obviously, I was wrong, because even the Cisco switch we put 
in to replace the EX4200 doesn't have label hashing, it 
still can load balance the MPLS-encapsulated traffic, 
perhaps just by IP address alone embedded within the MPLS 
payload.

Mark.
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