Cisco 2851 Capacity Question

[metropdx]

Hello,

I am turning here after spending hours of searching online. Hoping for some sort of confirmation of my suspicions. I manage the servers at my work and the network is mangaged by another group. I am concerned that the router we have is underpowered. It is a Cisco 2851. I am not sure how much RAM it has. Currently, we have about 700+ hosts (600 of which are on the same segment) connecting through it daily. The pipe that goes from it to our exteral data center in another city (stated 24Mbps, but really more like ~10Mbps) carries Notes email, DFS, AS400 client session, Internet (heavy), and ECM app traffic for 500+ users. Coming back up that pipe, for access to a DC in our server room, is traffic from several other outlying offices.

I have asked the network group about the status of the router and have repeatedly been told "everything's fine". We continue to experience outages of the services that go out through the router; but when this happens, services on our local net are still available (e.g. DFS goes out but I can ping the local server and unc to the share that is in the DFS root by name and IP).

I am uncertain what services are running on this router. It might not have anything but basic routing turned on; but from my research it seems that this router is not designed to handle the amount of traffic that we are pounding it with. Does anyone out there have experience with a similar router / scenario? I would contact Cisco directly; but don't want to just fall right into a sales pitch. If the router is capable, then it is capable and I will continue my troubleshooting. We originally suspected broadcast storms, but can find no evidence of a storm when the problems occur.

Thanks in advance. Any advice is greatly appreciated!

 

[SweetRevelation]

Hello metropdx,

The short answer is that a Cisco 2851 should be MORE than enough for a 24mbps connection, but it could have configuration issues, CEF being disabled or something.

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

That's a list of throughput performance of various cisco routers.

I'm currently using a 2851 on a DS3 and it has no trouble processing the load of the 45 meg circuit, that sheet shows CEF capability of over 100 meg.

Are they firewalling IPSing anything like that?

It's more likely to be a circuit issue than a router issue I would think. Just my two cents.

-
Chris

 

[metropdx]

Thanks for the reply Chris. If I am understanding you correctly, it sounds like it may be more of a bandwidth issue. Maybe we are maxing out the +/- 10Mbps of actual bandwidth that we have?

My concern is, for instance, even if you have a really good 1Gbps server NIC and you try and cram 200Mbps traffic down its throat with the connections coming from 500 different machines simultaneously, well at least in my experience it's going to start to choke up. I was worried that maybe something similar was happening to this router. That said, it seems that the limiting factor may very well the size of the pipe connecting the two data centers.

I have read the performance specs that you linked. Unfortunately, I do not have access to the settings or performance logs on this router to compare. All I have is the assurance from the network group that it is "configured and working properly".

From what I have read on Cisco's website, this is not an enterprise class router. Yet we seem to have enterprise class traffic here. Cisco states that this is an SMB router. I have seen other posts indicating that anything more than 250 some odd host connections steps into enterprise class needs and we are talking about 700+ hosts here. Hence my concerns.

I will further investigate the usage of our bandwidth and see if that yields any additional information.

 

[dgrizzard]

I can say from experience that if you have a 24Mbps connection (you are seeing 10, is this a cable modem?) for 500+ users for all services then it is not enough. Its not even enough for just internet.

I have a DC connecting 5 other heavy offices via 100MB MetroE, total users are about 500-550 for our main office and the other 4, and we spike to 50-60Mbps regularly and our average is about 15-20Mbps.

This is for all traffic including internet/etc.

 

[dgrizzard]

Follow up...

Your network people may or may not be doing this, but the best thing to do is run Netflow on the router and see what your actual usage is.

 

[SweetRevelation]

Agreed, at the very least they should be able to get you some sort of utilization information on the circuit, if it's constantly pegged at 24 megs and queuing and dropping packets it's time for a larger circuit.

That's part of their job as network people to monitor capacity and utilization and reliability.

 

[metropdx]

I want to thank everyone for the replies. This information is very helpful to me.

The network crew we have is very good to work with. However, the division between our departments is sometimes "politicized". So dealing with issues like these can be tricky. I hate to have to second guess anyone, especially co-workers that I respect as experts in their field. But after several months of these issues and nowhere else to look I have to start trying to overturn the stones I am not allowed to look under so to speak.

I think some of the key words here are "queueing and dropping packets". From my research, this seemed to be what was going on under heavy load. Thank you all for helping me to focus in on the potential cause.

As for our circuit, it is provided by an intra-gov agency. They state that it is 24Mbps; but the network guys have said that they feel that it is much less than that, more like ~10Mbps. As for the specifics of the circuit, I have none. At this point though, I am wishing it were something more like 100MB MetroE!

My boss has requested some bandwidth reports. Hopefully we get them.