EtherChannel cross multiple WS-X6148A-GE-TX modules

Unanswered Question
Apr 13th, 2008

Hi,

The backplane of WS-X6148A-GE-TX have 8:1 oversubscribe, but it havn't the 1Gbps EtherChannel limitation. Can I create EtherChannel cross multiple WS-X6148A-GE-TX modules? ( for example : Module 7-9 are WS-X6148A-GE-TX, bundle Gi7/1-4 & Gi8/1-2 & Gi9/1-2 as an EtherChannel )

Best Regards,

Jackson Ku

I have this problem too.
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Jon Marshall Sun, 04/13/2008 - 23:49

Jackson

From Cisco doc

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The WS-X6148A-GE-TX switching module has 48 oversubscribed ports in six groups of eight ports each:

Ports 1, 2, 3, 4, 5, 6, 7, 8

Ports 9, 10, 11, 12, 13, 14, 15, 16

Ports 17, 18, 19, 20, 21, 22, 23, 24

Ports 25, 26, 27, 28, 29, 30, 31, 32

Ports 33, 34, 35, 36, 37, 38, 39, 40

Ports 41, 42, 43, 44, 45, 46, 47, 48

The eight ports within each group use common circuitry that effectively multiplexes the group into a single, nonblocking, full-duplex Gigabit Ethernet connection to the internal switch fabric. For each group of eight ports, the frames that are received are buffered and sent to the common Gigabit Ethernet link to the internal switch fabric. If the amount of data received for a port begins to exceed buffer capacity, flow control sends pause frames to the remote port to temporarily stop traffic and prevent frame loss.

If the frames received on any group exceeds the bandwidth of 1 Gbps, the device starts to drop the frames. These drops are not obvious as they are dropped at the internal ASIC rather than the actual interfaces. This can lead to slow throughput of packets across the device

If more throughput is required, either use ports from a line module that does not use oversubscription, or use ports from different port-groupings on oversubscribed line modules. For example, if the line module has 48 ports in groups of eight, you can select ports 1, 9, 17, 25, 33, and 41 for the same port channel.

Cisco recommends that you use 61xx, 63xx, and 64xx modules for access layer as they are usually oversubscribed and always have only a bus connection to the backplane switching bus. For a backbone connection, it is recommended that you use 65xx or 67xx modules which always have either an eight or 20 GB dedicated connection to the switch fabric.

=============================================

So you could create the etherchannel using ports from different groups on the same module or you could do as you suggest and use ports across multiple modules. Either way you need to make sure you are not using ports from the same group.

Jon

jackson.ku Mon, 04/14/2008 - 00:35

Hi,

If I bundle ports in different groups ( for example : port 1 & 9 ), but I still use other ports ( for example : port 2, 3, 10, 11 ) to connect servers, and these server have heavy traffics. Does the EtherChannel problem still occur?

Best Regards,

Jackson Ku

Jon Marshall Mon, 04/14/2008 - 00:45

Jackson

Each groups of 8 ports supports 1Gbp. So if you connect anything else to the port group then this will affect the throughput of the 8 ports so yes it would affect the Etherchannel. These blades are not really meant for this kind of this, they are heavily oversubscribed so if you wanted the full throughput you would need to have a lot of unused ports.

Jon

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