Flooding across VLANS

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Nov 30th, 2009
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I have attached a power point for your review.  We are seeing excessive packets jumping VLANS so-to-speak.  On the drawing you will see XYZ receiver which sends out boatloads of UDP packets (i.e., broadcasts constantly).  We are OK if they remain confined to VLAN 30.  However, they are jumping across a non-trunked link to VLAN 40.  The excessive broadcasts are affecting our ABC system's performance.  The switches involved are a Cisco Catalyst 4948 and a Cisco Catalyst 3500.  Any idea what command I can enter or remove to eliminate the unwanted traffic?


Thanks,

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Jon Marshall Mon, 11/30/2009 - 14:58
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Perhaps you could post the configs.


You have a non-trunked link going from vlan 40 on one switch to vlan 90 on another which doesn't really make sense.


Also can you explain what the "earnhardt server" is doing ? It seems to have connections to vlan 20, 30 and 90 on the trailer switch ?


Jon

gdwingnuts Mon, 11/30/2009 - 15:39
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It will take some time to post the configs.  I will begin that process.  Our developers told me they have merely linked the two switches between those VLANS...no trunking protocol.  The Earnhardt Server runs application software.  After looking at our sniffer data the packets appear to be coming from the XYZ server.  There showing up on our other switch (i.e., 3500 XL).  It just seems that the XYZ's broadcasts should be confined to it's own VLAN...correct?


Thanks,

Jon Marshall Mon, 11/30/2009 - 15:43
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gdwingnuts wrote:


It will take some time to post the configs.  I will begin that process.  Our developers told me they have merely linked the two switches between those VLANS...no trunking protocol.  The Earnhardt Server runs application software.  After looking at our sniffer data the packets appear to be coming from the XYZ server.  There showing up on our other switch (i.e., 3500 XL).  It just seems that the XYZ's broadcasts should be confined to it's own VLAN...correct?


Thanks,

If you have connected your 2 switches together but not with a trunk port then if the port is vlan 40 on the 3500 and vlan 90 on the traffic switch those vlans have effectively been joined together. You need to check the config of the ports.


If the earnhardt server has connections to both vlan 90 and vlan 30 then it could be passing traffic from vlan 30 to vlan 90 which is joined to vlan 40 on the other switch.


Of course this is speculation without knowing


1) what the config of the ports linking the 2 switches are

2) what the earnhardt server is actually doing


Jon

gdwingnuts Fri, 12/04/2009 - 08:31
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Thanks Glen,


I will have have to repost.  I provided some incorrect data.


Thanks,

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