Solved: 7604 upgrade RSP720-3CXL-GE to RSP720-3CXL-10GE?

Kevin Hamilton · ‎12-08-2023

Hello All. I have a 7604 router with two RSP720-3CXL-GE, one WS-X6704-10GE and one WS-X6748-SFP, so all my slots are full. I need to add two more 10GE ports. I'm leaning toward replacing the two RSP720-3CXL-GE with RSP720-3CXL-10GE, which would give me 2 10GE per card for a total of 4 more.

Does anyone have a different suggestion to accomplish adding 10GE ports without moving to a 7606, A9K or some other change of platform?

If I choose to replace the RSP720-3CXL-GEs with RSP720-3CXL-10GEs how should I do it? Can I replace one at a time and copy the running config from old to new? Can I pull the old RSPs and move FLASH to the new RSPs then install them? What is the best way to accomplish this?

Thank you, Kevin.

Joseph W. Doherty · ‎12-09-2023

You're correct, a full duplex port provides 2x port bandwidth.

However, the slot bandwidth is also 2x. I.e. a 6704 is NOT oversubscibed at 2:1.

As to whether ANY oversubscription ratio is acceptable, well that an "it depends" answer.

BTW, a 6708 shares 10g between port pairs. I.e. you can pair a lightly used port with a heavier used port. In your case, using six ports, two of those ports would not be sharing their 10g. (I recall, on 6500s, the 6708 can run in "performance mode" which deactivates half its ports. Used for cases where you need to guarantee no oversubscription.)

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Joseph W. Doherty · ‎12-08-2023

Personally, I don't know if compatible in the 7604, but what about the 6708 or 6716 10g line cards?

Kevin Hamilton · ‎12-08-2023

Hello and thank you for your response. I'm pretty sure the 6708 is compatible and I thought about swapping the 6704 for one. However it's my understanding the 7604 throughput is 40G per slot, so I would be way over subscribed. Thanks, Kevin

Joseph W. Doherty · ‎12-08-2023

Correct, the 67xx cards support 40g, so a 6708 is 2:1 oversubscribed.

But you noted you only need 2 extra ports, so expected usage will really be limited with only 40g?

Cannot say for RSP sups, but on the sup720s, their sup ports hardware resources were inferior to the better line card ports.

Kevin Hamilton · ‎12-08-2023

Hi Joseph. Thank you again for responding. I was told that when figuring slot bandwidth usage/capacity you have to account for upstream and downstream. So a 10G port should be counted as 20G. I have a 6704 with 4 10G ports. I was told to calculate that as 20G x 4, which would be 80G. So I'm already oversubscribed 2:1 in a 40G slot. If I change the 6704 for a 6708 then I'm at 160G so I'm oversubscribing 4:1.

Was I told the truth? If so, is a 4:1 oversubscription acceptable?

Kevin

Joseph W. Doherty · ‎12-09-2023

You're correct, a full duplex port provides 2x port bandwidth.

However, the slot bandwidth is also 2x. I.e. a 6704 is NOT oversubscibed at 2:1.

As to whether ANY oversubscription ratio is acceptable, well that an "it depends" answer.

BTW, a 6708 shares 10g between port pairs. I.e. you can pair a lightly used port with a heavier used port. In your case, using six ports, two of those ports would not be sharing their 10g. (I recall, on 6500s, the 6708 can run in "performance mode" which deactivates half its ports. Used for cases where you need to guarantee no oversubscription.)

Kevin Hamilton · ‎12-10-2023

Thank you very much for sharing your insights. You have been very helpful. I assume the port pairs are 1-2, 3-4, 5-6 and 7-8. Is that correct?

Joseph W. Doherty · ‎12-10-2023

I recall (?) that's correct.

Joseph W. Doherty · ‎12-10-2023

Oh, one last factoid. The line card's 40g is provided by two 20g fabric connections. I recall for a 6708, ports 1-4 use one 20g fabric connection while parts 5-8 use the other 20g fabric connection.