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4108 trunk not working

Occasional Visitor

4108 trunk not working

I have a 4108gl switch setup to trunk into a cabletron router. The issue I am seeing is all the outbound traffic from the switch is going out port#2 of the trunk. The inbound traffic is being evenly distributed by the cabletron.
We have tried setting the trunk to lacp and to trunk. Neither setting has made a difference. There are 10 server plugged into the switch via the 20port 10-100-1000tx + 2 mini-gbic card. Between the 10 severs they send about 70+ mbytes per second of data and handle about 1000+ connections. The 2port trunk is on a HPJ4864A transceiver module card with 3 J4131B gig sx cards installed. We are running firmware version 7.70..
I have tried turning routing on and off. With the routing turned on I have tried routing the traffic through the vlan ip and adding a static route of with the router ip as the gateway. Still no luck, any ideas?

Kell van Daal
Respected Contributor

Re: 4108 trunk not working

Hi Steve,

A few thoughts. Not sure if they are applicable for your situation.

Trunking uses SA/DA (source address/destination address, both mac-addresses) pairs to loadbalance between links in a trunk. The switch actually creates a hash from the SA/DA pair, and decides which link to use based on this hash.
So maybe the SA/DA pair hashes in your situation are the same for each traffic flow?

- Is the cabletron the default gateway for all the servers, so the servers do not first go through another router, which changes the SA and then to the cabletron? If so, the SA/DA pairs will be the same for each flow.

- Do you use a cluster method which uses the same SA for all servers?

- Are the MAC-addresses from all servers very similar? (same vendor and type for example) This could result in the same hashes for all SA/DA pairs. You could try manually changing a mac-address on a server to make sure a different hash will be created. Then check if that server will use another link in the trunk.

Hope this helps,

Occasional Visitor

Re: 4108 trunk not working

The Cabletron does host the default gateway for these servers and each server has its own live ipaddress. All the server are using Intel cards and I have tried changing the mac address twice on one of the servers but still no luck. Im going to try changing mac addr again later on and using the switch as the default gateway. Im surprised no one else has not had this issue.