site working slow and lots of Dup Ack on the network/VLAN....

Unanswered Question
Feb 2nd, 2007

Hi, I am expereincing a lots of Dup Acks , Retransmissions, TCP out of order when i sniff the traffic on my DMZ lan . Digging through forums i only came by MTU/MSS size issues and Speed Mismatch, but there is no such situation in my case I have dell power edge servers using Intel Pro 1 Gbps NICs with Linux OS which are connected to 6506E switch in a seperate VLAN for servers and the traffic flows through the CSS 11501 which has 100Mbps ports which is also connected to the same 6506E switch . I have manualls set the speed and Duplex of the CSS and other devices according to the port speeds and all the MTUS are 1500 (default) ,No CRC ,ERRORS or DROPPED packets on ant of the CSS,6506 or ASA interfaces ...What might be the possible cause of the Duplicates Acks.

I tested by placing servers on different loactions as marked in the diagram and go good resuls on two places as marked but when i put my servers on 6506 switch that is logically behind the DMZ port of ASA i get lots of retransmission and Dup Acks and my Site becomes slow.

I have this problem too.
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vijayasankar Fri, 02/02/2007 - 22:52


Could you please let us know, what was the speed/duplex settings of the server, when you placed the servers at the two places when you got better results?

Was it 100mbps/full or 1000mps/full.

Also let us know which party was retransmitting a lot?

Whether it was client retransmitting a lot towards the server or the server retransmitting a lot towards the server?


big_admin Tue, 02/06/2007 - 02:01

The Speed of the NIC was not modified when it was set at different locations as the NIC was in an Autonegotiating state.

Client side was aksing server that the packets are Out-of-Order (TCP out-of-order)

nyr.hakeem-habeeb Sun, 02/04/2007 - 20:25


Could try setting the MTU size on one PC to 1200bytes and test connectivity to server in the original location? Please post your outcomes.




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