2911 sufficient for full internet routing table?

[Patrick McHenry]

I was wondering what your thoughts would be on a 2911 for handling a full Internet routing table. We have two 2911s peering with two different providers using BGP and iBGP between the two 2911s.

We've been having some significant Internet slow downs recently and I wonder if the horse power of the routers could be an issue. When we experience the slowness the Interfaces don't seem taxed (although it is only a 100Mbps circuit and they are gig interfaces) and the show process cpu sorted doesn't show anything out of the ordinary. We plan on upgrading the circuit to 500 Mbps so if the router is being taxed now we might be in trouble.

Is there anything I should be looking at on the router when we are seeing the slowdowns?

Thank you, Pat

[Leo Laohoo]

2911 is NOT designed to push 100 Mbps of one-way traffic.  3925E or 3945 is more suitable for 100 Mbps (two-way traffic) with full BGP table (provided the DRAM has been upgraded up to it's eyeballs).  

500 Mbps, you will need to look at an ASR 1001-X or a 4451-X.

[Reza Sharifi]

Patrick,

As Leo also said it if you are looking to terminate a 500Mb circuit for your Internet access, you need to look at the ASR series and not the 3800 or 3900.  They don't have the horse power to push 500Mb line rate especially if you are planning to have full routing table which is close to 600k these days.

HTH

[Patrick McHenry]

Thanks for both of you getting back

Thanks for the confirmation - I was concerned about this myself. Is there a way I can prove that the router is not up for the job other than documentation? Meaning, other than reading a specs doc, how can I prove that the router is being over-worked? Is there some show output that will prove this?

Speaking of documentation where should I look for the listing of products and their bandwidth/routing table limitations?

Thank you, Pat

[Joseph W. Doherty · Accepted solution]

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The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

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Posting

Tracking your 2911's CPU usage will provide an indication of how hard it's being "worked".

I've attached a later Cisco document that better documents expected and recommended performance levels for various ISRs.  (NB: in that document, you'll see a 2911 is only recommended for up to 35 Mbps.)

PS:

BTW, running full BGP with your two ISPs, hoping to obtain optimal performance, really doesn't.  What actually works much better, if you're licensed for it, is Cisco's PfR technology (which will work fine with just a default to both ISPs).

[Patrick McHenry]

Thanks Joseph I will read the doc - could you point to the area that says the interface limit is 35Mpbs?

Can't seem to find it.

Thank you

[Joseph W. Doherty]

Disclaimer

The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

Liability Disclaimer

In no event shall Author be liable for any damages whatsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.

Posting

Figure 1, on last page.  The 35 Mbps is not a limit, but a usage "up to" recommendation.  Also, by WAN bandwidth, they also mean  full duplex (or 70 Mbps, overall).

[Patrick McHenry]

Sorry for throwing this into the mix, but the interface is really not a "WAN "connection - it is an Ethernet connection to the Internet provider. I know I said in an above post that it was a WAN connection - I apologize for the confusion.

And isn't the data sheet you provided assuming all the services are being used as well?

Also - just to add, I don't see any CPU spikes or memory utilization issues

Thank you

[Joseph W. Doherty]

Disclaimer

The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

Liability Disclaimer

In no event shall Author be liable for any damages whatsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.

Posting

Cisco recommendations are "generous" to insure you don't run short of CPU.

Cisco says "WAN" 'cause this is a "WAN" router.  Using a "WAN" Ethernet interface, I believe, may very slightly reduce overhead as framing is Ethernet to Ethernet.

If your current CPU utilization is okay, that's about the best measure because it's your real traffic.

[Patrick McHenry]

Thanks Joe. Then I'm going to assume we are on for now but when we go to 500mbps sec I'm thinking we need an upgrade. We do have a couple of spare 3900s laying around. Not sure how this response will format from my phone....

[Patrick McHenry]

Found it Thanks

[Patrick McHenry]

Hey - found this doc

http://www.cisco.com/web/partners/downloads/765/tools/quickreference/routerperformance.pdf

Says 2911 can handle 180 Mbps throughput

And we also have 2 GB of DDRAM - that should be enough for the BGP table correct?

Thanks

[Reza Sharifi]

Patrick,

I was going to post the same document for you.

2GB DDRAM should be enough to handle the routing table for now, but as you know it is always growing. Also, the 180 Mbps is for the whole box including all the interface. So, if you are bringing a 500Mb from circuit the and provider is guarantee this at line rate, the 2900 can't handle the speed. On the other hand, if the provider is committing at 100Mb and you can burst to 500Mb than the 2900 could be a possibility.

Also, have a look at this site for the current BGP routing table entries.

http://thyme.apnic.net/us/data-summary

HTH

[Patrick McHenry]

I didn't know that the 180Mbps was referring to all of the interfaces. So it is not referring to a per interface limit?

So, if we have a 100Mbps WAN connection, A 1000Gbps LAN connection and a 1000Gbps iBGP connection to the other internal Internet router, all three interfaces are included when considering the 180Mbps limit?

So, I understand that when we go to 500Mbps the 2911 isn't going to be able to keep up with the bandwidth requirments, but what about at 100Mbps? Do you think it is still an appropriate router?

Thank you

Thank you

[Reza Sharifi]

So, if we have a 100Mbps WAN connection, A 1000Gbps LAN connection and a 1000Gbps iBGP connection to the other internal Internet router, all three interfaces are included when considering the 180Mbps limit?

Correct. That is for whole box.  I personally would not use the 2911 for 100Mb, but would use 2921 or 2951.  

HTH