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New Member

problem with catalyst 6500 share bus

1.When I install one line card with switch fabric is connect to supervisor engine using CEF ( e.g. WS-X6516A-GBIC ), i want to know the 32Gbps share bus  is work together or don't work at all? total 8Gbps switch fabric channels + 32Gbps (share bus)?

2.Can DFCx card  increase the switch fabric channels or share bus? or enhance the forwarding performace like 30Mpps per system up to 15Mpps per slot? or enhance application performace such as ACL, QoS, L2 Switching etc.?

Could anyone explain this to me?

Thank you for any input.

Everyone's tags (1)
3 ACCEPTED SOLUTIONS

Accepted Solutions
Cisco Employee

Re: problem with catalyst 6500 share bus

Hi Shi,

Shared Bus would always remain there for your Line Card (WS-X6516A-GBIC) as it does not have an option for local forwarding engine (DFC). So the packets ingress on this line card, would send a brief packet header (depends on the switching-mode) on this shared Bus (dbus) to reach out to PFC (Supervisor) for forwarding decision. The forwarding result would be sent again on this shared Bus (rbus), and now the ingress Line card would use that information to send that packet out over fabric, if the egress port is on a different line card or fabric channel. Though, it would really matter if other line cards are also fabric enabled.

Certainly DFC would increase the forwarding performance, as the line card equipped with it, can take local switching decisions and entire traffic would flow over fabric.

I suggest you go through this document:

http://www.cisco.com/en/US/prod/collateral/switches/ps5718/ps708/prod_white_paper0900aecd80673385.html

Cisco Employee

Re: problem with catalyst 6500 share bus

32 Gbps is exclusively for Dbus, Rbus is not used by any Line card to send packets, but rather result sent by the Supervisor/PFC. CBus is rather EOBC which is all together a different Out of Band Channel for internal communication between Supervisor and Line cards, so is not part of that 32Gbps bandwidth, and is rather a half duplex Fast Ethernet connection.

Show fabric switching-mode, is the CLI which helps to identify the switching mode of the device.

Cisco Employee

Re: problem with catalyst 6500 share bus

In truncated mode, Classic Line card rely on Shared Bus for communication.

1) Ingress-Fabric Enabled LC(w/o DFC)------>Egress Classic LC

A truncated header would go over Dbus for forwarding decision from PFC, which would be put on Rbus. Then the entire packet would go over Fabric, irrespective of the destination LC, however it would go to Supervisor in above case. From the supervisor it would go over the shared bus to reach the classic Line card.

2) Ingress-Fabric Enabled LC(with DFC)------>Egress Classic LC

The only difference is that no truncated header would go over Dbus, as DFC is present for forwarding decision. Rest remains same.

3) Ingress-Classis LC------>Egress Fabric LC

Entire packet would be sent over Dbus, and then result over Rbus. The Supervisor would pick this packet and send it over Fabric to make it to Fabric enabled Destination Line card.

HTH.

Regards,

Deepak

6 REPLIES
Cisco Employee

Re: problem with catalyst 6500 share bus

Hi Shi,

Shared Bus would always remain there for your Line Card (WS-X6516A-GBIC) as it does not have an option for local forwarding engine (DFC). So the packets ingress on this line card, would send a brief packet header (depends on the switching-mode) on this shared Bus (dbus) to reach out to PFC (Supervisor) for forwarding decision. The forwarding result would be sent again on this shared Bus (rbus), and now the ingress Line card would use that information to send that packet out over fabric, if the egress port is on a different line card or fabric channel. Though, it would really matter if other line cards are also fabric enabled.

Certainly DFC would increase the forwarding performance, as the line card equipped with it, can take local switching decisions and entire traffic would flow over fabric.

I suggest you go through this document:

http://www.cisco.com/en/US/prod/collateral/switches/ps5718/ps708/prod_white_paper0900aecd80673385.html

New Member

Re: problem with catalyst 6500 share bus

Thank you for your answer.

But now I have three new question.

1.According to document "The DBus is the bus that realizes the bandwidth of 32 Gbps", that RBus and CBus share the bandwidth of DBus? or have the separate bandwidth?

2.How can I detect the system run on Compact mode or Truncated Mode?

3.In Truncated Mode, how classic line cards and fabric enable line card interactive? from switch fabric channel to DBus? or only transmit between DBus?

Cisco Employee

Re: problem with catalyst 6500 share bus

In truncated mode, Classic Line card rely on Shared Bus for communication.

1) Ingress-Fabric Enabled LC(w/o DFC)------>Egress Classic LC

A truncated header would go over Dbus for forwarding decision from PFC, which would be put on Rbus. Then the entire packet would go over Fabric, irrespective of the destination LC, however it would go to Supervisor in above case. From the supervisor it would go over the shared bus to reach the classic Line card.

2) Ingress-Fabric Enabled LC(with DFC)------>Egress Classic LC

The only difference is that no truncated header would go over Dbus, as DFC is present for forwarding decision. Rest remains same.

3) Ingress-Classis LC------>Egress Fabric LC

Entire packet would be sent over Dbus, and then result over Rbus. The Supervisor would pick this packet and send it over Fabric to make it to Fabric enabled Destination Line card.

HTH.

Regards,

Deepak

New Member

Re: problem with catalyst 6500 share bus

Appreciate your answer very much.

Thanks a million.

Cisco Employee

Re: problem with catalyst 6500 share bus

32 Gbps is exclusively for Dbus, Rbus is not used by any Line card to send packets, but rather result sent by the Supervisor/PFC. CBus is rather EOBC which is all together a different Out of Band Channel for internal communication between Supervisor and Line cards, so is not part of that 32Gbps bandwidth, and is rather a half duplex Fast Ethernet connection.

Show fabric switching-mode, is the CLI which helps to identify the switching mode of the device.

New Member

Re: problem with catalyst 6500 share bus

Thanks in advance!

I have updated the question as above just now.

I'm sorry to trouble you again.

Question

In Truncated Mode, how classic line cards and fabric enable line card interactive? from switch fabric channel to DBus? or only transmit between DBus?

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