[alcatel-nsp] unbalanced traffic on GigEs in a LAG

Scott Weeks surfer at mauigateway.com
Mon Mar 8 19:17:46 EST 2010

--- philxor at gmail.com wrote:
From: Phil Bedard <philxor at gmail.com>

I guess it's hard to know exactly which services are flowing across the 
link but if it's only acting as an LSR then it should be hashing based 
on the MPLS stack (Up to 5 labels), ingress port, and system ID.   Are 
there any potential really high BW services across the LAG?  With the 
IOM3/IMM you can have it hash on both the labels and the IPv4 header, 
but not on the IOM2.  

If there are services originating on the box there are all kinds of 
rules on how things are hashed on egress, but LSR it's pretty simple.  

We carry our internet traffic in a VPRN.  This is 99+% of all traffic.  
I'm guess I'm going to have to go with just 2 cases of bad load 
balancing.  The network goes something like this:

br1     br2
 |       |
 |       |
|\       /|
| \     / |
|  \   /  |
|   \ /   |
|    X    |
|   / \   |
|  /   \  |
| /     \ |
|/       \|

No links are full.  The 'middle' is 10G and the 'edges' are multi-GigE.  br1 has about twice the bandwidth as br2, so perhaps the label from br2 is hashed over one of the 2 GigEs (above the arrow) and the label of br1 is over the other  and it's just a case of bad load balancing.  More that 10 to 1, though, seems excessive.

Thank you everyone on and off-list for your help.  :-)

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