Description of problem: quoting the customer: We have network issue's between guests and servers not on the same host (can be other guest on other hosts or normale servers). We discovered that this is related to IPv6 and GSO in the virtio-net driver. This is reported in also at: - http://www.mail-archive.com/kvm@vger.kernel.org/msg28045.html This one looks also related: - https://bugzilla.redhat.com/show_bug.cgi?id=490266 For a workaround, turning of GSO (options virtio_net gso=0) on the guests solves the problem for linux guests. We are not sure yet how to do that on windows. However I am sure this problem is generated on the host so it should be a bug in the kernel on the host. What we see is that the jumbo/super frames generated by the guests (due to GSO being enabled) are not correctly fragmented by the host at the moment it should leave the physical NIC. Disabling GSO/TSO on the NIC with ethtool on the host does not help. Version-Release number of selected component (if applicable): 2.6.18-194.el5 How reproducible: always Steps to Reproduce: 1. configure a virtio_net VM with IPv6 2. configure a http server with IPv6 in same subnet 3. configure wget to use IPv6, and add the http server to hosts file with it's IPv6 address 4. wget a large file - watch the speeds drop drastically Actual results: very slow speeds (avg of 1-2mbps on a 1Gbps network) Expected results: normal download speeds Additional info:
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This request was evaluated by Red Hat Product Management for inclusion in a Red Hat Enterprise Linux maintenance release. Product Management has requested further review of this request by Red Hat Engineering, for potential inclusion in a Red Hat Enterprise Linux Update release for currently deployed products. This request is not yet committed for inclusion in an Update release.
Created attachment 483203 [details] proposed patch
Patch(es) available in kernel-2.6.18-248.el5 Detailed testing feedback is always welcomed.
According to comment #19, moving this bug to VERIFIED.
An advisory has been issued which should help the problem described in this bug report. This report is therefore being closed with a resolution of ERRATA. For more information on therefore solution and/or where to find the updated files, please follow the link below. You may reopen this bug report if the solution does not work for you. http://rhn.redhat.com/errata/RHSA-2011-1065.html