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Throughput Issues - 2960 <-> ASA 5520

I am having some Strange issues regarding throughput between several trunked vlans when passing the ASA.


2960-2 (vlan 1-5) <-- trunk --> 2960-1 (vlan 1-5) <-- trunk --> ASA 5520 (Ge0/1.1-5)

As soon as flows traverse the ASA i have issues with really slow traffic (1-2Mbit max).

I already updated the ASA to the 8ED release but nothing changed.

There is a hint for the problem on the Ge Interface on 2960-1 in terms of "undersize packets"

Port Align-Err FCS-Err Xmit-Err Rcv-Err UnderSize

Gi0/2 0 0 0 4 3247978

Consulting the "Troubleshooting Switch Port and Interface Problems" guide i end up with following not so usefull info.


This is an indication of a bad frame generated by the connected device. Verify that the connected device operates correctly.

[quote end]

Unfortunately there are no signs of interface errors on the ASA interface and the corresponding subinterfaces.

Anyone a hint how to troubleshoot this the best way or find the source of the problem.

Software Images:

ASA -> 8.0(2)

2960 -> 12.2(35)SE

Thanks for reading...


New Member

Re: Throughput Issues - 2960 <-> ASA 5520

Having a similar problem with my ASA

Getting around 100Kb/s with a 100Mbit local lan connection.. If I use my older 515E it gives me top notch speed....

New Member

Re: Throughput Issues - 2960 <-> ASA 5520

found my problem, damn switch went half-duplex on me

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