The 3750 only has a limited amount of TCAM that must be used for routing
(CEF entries) switching (for MAC entries), multicast and qos queues.
Sometimes the "default" allocation of TCAM isn't right and you have to
adjust it.
Do the MAC entries for the servers exist in "show mac-address-table", if
not you probably have an TCAM issue. Also do a "show mac-address-table
count" and see how many entries are left for MAC addresses (this will be the
last line of the output). If you are doing layer 3 on the switch then you
probably don't have enough TCAM allocated for CEF entries, and the reason
you are having issues.
The "show sdm prefer" command will show you what is currently configured.
The default is "default" but we have had to change this on 3750's that we
are doing layer 3 switching on. To change it, issue a "sdm prefer
<template>" command, and you will need to reboot for it to take effect.
See this article for more information on TCAM and the 3750.
http://www.enterprisenetworkingplane...le.php/3527301
"Aaron" <> wrote in message
news:27d46f52-5c8c-4752-baec-...
> So I'm tossing this out there to see if anyone might have some
> thoughts on where to look because I just find this baffling.
>
> We had a Cisco 3750 Catalyst switch set up with a number of hosts
> connected to it. All of these hosts were configured to do NIC teaming
> with etherchannels set up on the switch. We then added a second 3750
> to create a stack. We re-configured the etherchannels on the existing
> servers so that each one had one connection to each switch. We then
> added a number of new servers with each one using etherchannels (one
> connection to each switch). Everything seemed fine. All of the
> servers were available on the network, etc. But, we noticed that of
> the 12 new servers, two of them had this odd issue. All of the
> servers are in the same VLAN and IP's in the same subnet. All of them
> can get out to the internet and can be reached by *most* computers in
> the same VLAN and in other VLANS. BUT...the two oddballs can't talk
> to the other servers connected to the same 3750.
>
> I turned off the NIC teaming and disabled the secondary NIC port. We
> removed the switch ports from the etherchannel so it was just a
> normal, plain jane port. Still had the problem. Moving the server IP
> information from the primary to the secondary NIC port cleared up the
> problem...at first. While trying various permutations of the NIC
> teaming (trying to track down the problem) things got the point where
> if the server was configured to use NIC1, it could get out to the
> internet and other various servers, but couldn't talk (no ping, no
> thing..they don't even see ARP requests) to the other servers on the
> switch (EXCEPT those in a different VLAN) or some other random
> machines on that same VLAN.). Setting the server to use NIC2 resulted
> in it being able to talk to servers it previously couldn't talk to,
> but it suddenly couldn't talk to the gateway and so couldn't reach
> anything else. It was previously able to do so.
>
> What this FEELS like is that the switch has somehow declared these two
> server's MAC addresses as persona non-grata and won't route traffic
> from or to it except to seemingly random exceptions.
>
> Anyone have any thoughts on where to look as I'm pretty much stumped
> at this point.
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