[c-nsp] Bundling ports on different WS6704 linecards

[Rin]

A friend of mine suggests that all linecards should have the same DFC (3C,
3CXL, 3B etc...), else the port channel might not work properly. 
In our case, all of the linecards are DFC3B & no service modules will be
used so I believe it should be ok. 

Thanks,

-----Original Message-----
From: cisco-nsp-bounces at puck.nether.net
[mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Ivan
Sent: Tuesday, August 10, 2010 3:02 AM
To: cisco-nsp at puck.nether.net
Subject: Re: [c-nsp] Bundling ports on different WS6704 linecards

On 9/Aug/2010 11:22 p.m., Phil Mayers wrote:
> On 09/08/10 08:47, Rin wrote:
>> Hi group,
>>
>>
>>
>> We are building a Core network of 3 7609 routers connecting as a 40Gbps
>> ring. On each router we have 4 WS6704 linecards. Each router will be
>> connected to other routers via 4 10G-links, these links will be
>> configured
>> as Port-Channel.
>>
>>
>>
>> Should we place each link of the port-channel on different linecard on
>> each
>> router or should we allocate all 4 links on the same linecard? Anyone has
>> any problem with configuring etherchannel for ports on different WS6704
>> linecards?
>
> We do that extensively. It works fine. It is better to have
> cross-linecard portchannels in general.
>
> HOWEVER - there are a couple of caveats to be aware of. One is if you've
> got different linecards with different QoS queuing, you will need:
>
> int PoX
> no mls qos channel-consistency
>
> Second is that there are some issues with cross-linecard portchannels if
> you have service modules (ACE, FWSM, WiSM) in the chassis. I can't
> remember the details or find the link at the moment.
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I was bitten by the FWSM and DEC.  The link that was referred to is
probably http://www.cisco.com/en/US/ts/fn/610/fn61935.html

Field Notice: FN - 61935 - Catalyst 6500 Series and 7600 Series Service
Module Incompatibility With Distributed EtherChannel and Packet
Re-Circulation

"Problem Description
When the listed service modules transmit packets to VLANs also used with
Distributed EtherChannel (DEC), those packets may be dropped and lost.

Background

The listed service modules do not support packet re-circulation. Packet
re-circulation is a specific means to forward packets internal to the
chassis between modules. When the service module attempts to forward a
packet onto such a VLAN with packet-recirculation enabled, it may fail and
the packet might be lost. When packet re-circulation is not enabled on the
destination VLAN, even if DEC is present, this problem will not be
encountered."

We ended up getting rid of the DEC and using plain EC and "no monitor
session servicemodule" as the span sessions were required for other
purposes.
(http://www.cisco.com/en/US/products/hw/modules/ps2706/products_qanda_item09
186a00801e9e26.shtml#q44)

Cheers

Ivan
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