Need Help with Cisco 6513 Switch

tom.oleary · ‎02-26-2012

I'm a recent Grad and just started to work for a cloud provider. The Senior Engineer gave me a project and thought this would be a good place to start to get some help. We have a Cisco 6513 Switch. During some parts of the day it is having large amounts of transmit discards on a certain interface because of the amount of data we are pushing. We have determined it is a link problem and not a problem with the switch. The link cannot handle the amount of packets the switch is pushing out. I was wondering if there is a way to create a buffer or a way to regulate the maximum amount of packets that can leave that interface without losing any packets? Thanks for the help!

swordcrowned · ‎02-26-2012

Thomas,

Is creating an etherchannel an option?

Bryan

tom.oleary · ‎02-26-2012

We have a port channel configured that uses 2 Gigabit interfaces through 2 different ISPs, one of them being the problem. I asked the senior engineer if we would be able to load balance between the 2 and he explained to me that somehow the application is picky and chooses the route and, for some reason, cannot be changed. Does this help?

Pronoy Dasgupta · ‎02-26-2012

Hey Thomas,

I am trying to understand this last part, where you mention the 2 Gig port channel through two different ISPs? Are you trying to say that there are 2 different port channels with 2 interfaces each in them?

When you say discards, what is the frequency of the increase in discards? And do these discards appear on the interface to which the server is connected to or the uplink interfaces?

What kind of line cards are you using on the 6500?

Are you using QoS on this switch?

Normally, the ethernet line cards on the 6500 have a bunch of front end interfaces mapped to an ASIC. When you see drops on the interface, the packets are basically being dropped on the ASIC. One workaround, would be to space out the interfaces in such a way that the higher used interfaces are not grouped to the same ASIC. I can explain this further, however if you would let us know of the above, I think it might help us reach a possible solution / workaround.

HTH

Pronoy

tom.oleary · ‎02-26-2012

Hi Pronoy,

There is one Gigabit ethernet interface that goes to one ISP and another Gigabit ethernet interface that goes to the other ISP. They are configured on the same port channel. Also, we don't see these discards on the switch but, we have a NMS that monitors the link. These discards are on the uplink interface. As for the other questions, I'll have to get back to you.

Thanks for the help!

Pronoy Dasgupta · ‎03-10-2012

Hey Thomas, took me a little time to get back to this. However what do you mean when you say that the discards on not on the switch but on the uplink interfaces?