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Beginner

Replacing a 7206VXR w/ NPE-G1 with Sup720-3BXL w/ WS-X6408A-GBIC

Hi,

Our Internet BGP tier is currently provided by a pair of 7206VXR routers with NPE-G1s which are getting quite long in the tooth. We've recently been able to reclaim a pair of Sup720-3BXLs and the associated 6509 chassis'. Its our intention to retire the 7206s and replace them with the 6509s /w Sup720s but we require 6 GigE interfaces per box. We have a pair of WS-X6408A-GBIC 'classic bus' linecards on the shelf (no spare 65XX or 67XX modules unfortunately) but my question is whether using the WS-X6408A-GBIC to provide port capacity is a good or bad idea in this scenario?

I appreciate that using a WS-X6408A-GBIC means that the classic 32Gbps shared bus will be used (with a max of 15Mpps per system) but in raw performance numbers this is a significant increase on the 7206VXR/NPE-G1s ~2Gbps backplane and ~1Mpps forwarding rate.

My real concern is that I've found two different Cisco documents that describe the Forwarding-Engine Architecture differently for classic linecards.

This link :-

http://www.cisco.com/en/US/prod/collateral/switches/ps5718/ps708/product_data_sheet0900aecd801459a7.html

states that "the Supervisor engine CPU makes forwarding decision"

and this link:-

http://www.cisco.com/en/US/prod/collateral/switches/ps5718/ps708/product_data_sheet0900aecd8017376e.html

states that "Centralized Cisco Express Forwarding engine located on supervisor policy feature card (PFC) makes forwarding decision"

As the 6500 series is a hardware-based platform I'm keen to make use of hardware-supported features where available and not experience unexpected issues from high CPU utilisation.

Can anyone confirm exactly how traffic will be forwarded by the Sup720-3BXL with a WS-X6408A-GBIC in the chassis?

Thanks in advance

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Hall of Fame Mentor

Re: Replacing a 7206VXR w/ NPE-G1 with Sup720-3BXL w/ WS-X6408A-

If that's your proposed design, then it should be fine. The problem you may run into if you were to have a fully loaded switch with traffic in the shared bus. Having a CEF720 would improve throughput on such situation but as I said, with the few ports you are using, you should be fine.

Also, please note - regular line cards on 6500 do not support extensive QoS such as CBWFQ and Shaping.

You need a WAN module for such features.

These features are available w/ the 7200 platform so you will be missing those features if they were in used with your previous configuration.

Regards,

Edison

View solution in original post

3 REPLIES 3
Hall of Fame Mentor

Re: Replacing a 7206VXR w/ NPE-G1 with Sup720-3BXL w/ WS-X6408A-

Both documents are correct. I believe the first document refers to the CPU because that's where the packet is sent but in reality the forwarding decision is made by the Supervisor's PFC.

The process will be done in hardware thus you should be fine. With that said, I strongly suggest installing a CEF720 module instead of going with a classic line card. Classic line cards are designed for host connectivity, not for server connectivity nor internet connectivity.

Regards,

Edison

Beginner

Replacing a 7206VXR w/ NPE-G1 with Sup720-3BXL w/ WS-X6408A-GBIC

Thank you for the reply. Are you able to elaborate a bit more on the cons of using a classic line card like the WS-X6408A-GBIC in this situation. At present each 7206 has a GigE ISP link providing a full internet routing table with the other interfaces being firewall interface connections and a direct iBGP connection between the 7206s.

I was thinking of using the GigE interfaces on the Supervisors themselves for the ISP connection(s) and iBGP link with the WS-X6408A-GBIC proving the firewall links (there is also a possibility of being able to use dual sups per chassis which means only a couple of ports would be used on the WS-X6408A-GBIC).

Hall of Fame Mentor

Re: Replacing a 7206VXR w/ NPE-G1 with Sup720-3BXL w/ WS-X6408A-

If that's your proposed design, then it should be fine. The problem you may run into if you were to have a fully loaded switch with traffic in the shared bus. Having a CEF720 would improve throughput on such situation but as I said, with the few ports you are using, you should be fine.

Also, please note - regular line cards on 6500 do not support extensive QoS such as CBWFQ and Shaping.

You need a WAN module for such features.

These features are available w/ the 7200 platform so you will be missing those features if they were in used with your previous configuration.

Regards,

Edison

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