Cisco Support Community
Showing results for 
Search instead for 
Did you mean: 

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. And see here for current known issues.

New Member

Lots of duplicate Ack's

I have a 6509 switch with 7 48 port gig blades completely full and am wondering if it is being overloaded. There are about 40 servers running gig and the rest is workstations/ip phones at 100 meg. All are on a single VLAN.

What I am seeing when I run a capture transferring a 60 meg file, it only takes a second or two between servers but I see about 900 duplicate Ack's with about 100 frozen windows. I've tested on various servers and see somewhat the same thing with some having a lot of  retransmissions.

This does not seem normal but wanted to ask others what they think. I am wondering if the broadcast domain is not the cause of the problem. If this is not normal, how can I best determine what the tru problem is?

New Member

Re: Lots of duplicate Ack's

All on one Vlan? This setup, while simple to manage, is most likely wreaking havoc on several different levels. The first thing I would do, in this case, would be to move the VoIP off into its own Voice vlan, with a good router that has specific support for VoIP vlans. Cisco makes several excellent ones, and this will alleviate quite a bit of traffic on your primary data network. It will also offer a more managable QoS. Second I would guess from the large number of used ports there are at least 50-100 workstations on the network in question, and these can be divided up into thier own Vlans based on location, dept, or whatever. This will give you a more organized setup to the network (but this can be done at a later time as this will most likely cause some downtime during reconfig.) There are additional ways to alleviate traffic and allow routing between the multiple subnets and offer you more control on route, permissions, load-balancing and several other benefits. First and foremost, I would suggest the removal of the VoIP traffic from your primary Vlan and then begin planning the design of the network beyond that point.