[nsp] Per-packet load sharing on Eng2 LC???

[Bruce Pinsky]

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Raymond, Steven wrote:

| Okay, please tell me what the real implication is here:
|
| Router#config t
| Enter configuration commands, one per line.  End with CNTL/Z.
| Router(config)#int Serial10/0/15:0
| Router(config-if)#ip load-sharing per-packet
| % Warning: Engine 2 and/or 3 linecards present.
| Traffic inbound on Engine 2/3 linecards will not be per-packet loadshared.
|
| S10/0/015:0 is a customer-facing eng 0 CT3 GSR linecard 6CT3-SMB=.  The
| backbone interface is an eng 2 OC48 SRP/DPT OC48/SRP-SR-SC=.  So does the
| above message mean it is completely impossible to load-balance per-packet
| outbound when the ingress card is eng 2/3?
|
| What then does it do?  Per-destination load-balancing?  Hopefully I am
| simply misinterpreting what IOS was kind enough to warn me about.  Otherwise
| I'll be left wondering if yet again I've been bitten by a linecard/engine
| rev performance/feature limitation that always seem to crop up after
| deployment.
|

According to the feature info for 12.0(21)S at:

http://www.cisco.com/en/US/partner/products/sw/iosswrel/ps1829/products_feature_guide09186a0080087c5b.html

here are the supported engines:

	Note   In the Cisco 12000 series Internet Router, per-packet load
balancing is supported only on Engine 0 (E0), Engine 1 (E1), and Engine 2
(E2) line cards.

And this note regarding configuring the load balancing the same across all
the E2 cards:

~ 	Configuring Load Balancing in the Same Way on All E2 Line Cards

	You must globally configure load balancing on E2 line cards so that it is
performed either in per-destination or per-packet mode. It is not possible
(as in other Cisco IOS software-based platforms) to configure some packet
prefixes in per-destination mode and others in per-packet mode. Although
you could configure one E2 line card in one load balancing mode and all
other E2 line cards in the other mode, this would not be practical and
would result in a limited use of the router. For this reason, Cisco
recommends that you configure load balancing on all E2 line cards in the
12000 Series Internet Router in the same way: either per-packet or
per-destination.


However, I found these notes for 12.0 mainline at
http://www.cisco.com/en/US/partner/products/sw/iosswrel/ps1828/products_command_reference_chapter09186a00800881f8.html#1017705:

	Note   Per-packet load balancing via CEF is not supported on Engine 2
Gigabit Switch Router (GSR) line cards (LCs).

	Note   If you want to enable per-packet load sharing to a particular
destination, then all interfaces that can forward traffic to the
destination must be enabled for per-packet load sharing.


So, I think the first question is one of which version you are running on
your GSR.  If you are running 12.0M, then it seems you will need to upgrade
to get E2 support.  If you are running at least 12.0(21)S, then you may
need consistent load-balancing method on all the ingress interfaces that
will feed to the egress interface.

- --
=========
bep

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