[j-nsp] Juniper EX4550 load balancing of MPLS over LAG

[Erdal Rasid]

Just sharing. maybe it saves your time when it pops up on next search.

yes, EX4550 does load balancing of MPLS packets over LAG links

and no, not always working as eloquently explained in (yes, cisco link :) )

https://supportforums.cisco.com/t5/service-providers-documents/asr9000-xr-load-balancing-architecture-and-characteristics/ta-p/3124809#L3

In order to comply with that thought process, we check the first nibble following the MPLS header and if that starts with a 4 (ipv4) or a 6 (ipv6) we ASSUME that this is an IP header and we'll interpret the data following as an IP header deriving the L3 source and destination.

Now this works great in the majority scenarios, because hey let's be honest, MAC addresses for the longest time started with 00-0......

This fools the system to believe that the inner packet is IP, while it is an Ether header in reality.

Bottom line is that if your DMAC starts with a 4 or 6 you have a situation.

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Solution
Use the MPLS control word.


as for the question : can HASHing be influenced on the 4550’s ? 
officially no, but then again officially on juniper documentation ex4550 does not do mpls load balancing 

regards,
REM