<div dir="ltr">The tap interfaces from QEMU, and the veth pair from the qbr linux bridge to the br-int OVS integration bridge also need to be configured for jumbo frames. This article may help to get the lay of the land: <a href="http://openstack.redhat.com/Networking_in_too_much_detail">http://openstack.redhat.com/Networking_in_too_much_detail</a> It's a good idea to configure all interfaces on an L2 segment with the same MTU (at least all the interfaces with IP addresses, and ensure any L2 interfaces have the same or larger MTU) otherwise path MTU detection doesn't work.<div>
<br></div><div><br></div><div>Dustin Lundquist</div></div><div class="gmail_extra"><br><br><div class="gmail_quote">On Thu, Aug 28, 2014 at 7:47 PM, Tong Manh Cuong <span dir="ltr"><<a href="mailto:cuongtm@vdc.com.vn" target="_blank">cuongtm@vdc.com.vn</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div lang="EN-US" link="#0563C1" vlink="#954F72"><div><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Tahoma","sans-serif";color:#1f497d">Dear experts,<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Tahoma","sans-serif";color:#1f497d"><u></u> <u></u></span></p><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Tahoma","sans-serif";color:#1f497d">My issue is that:<u></u><u></u></span></p>
<p><u></u><span style="font-size:11.0pt;font-family:"Tahoma","sans-serif";color:#1f497d"><span>1.<span style="font:7.0pt "Times New Roman""> </span></span></span><u></u><span style="font-size:11.0pt;font-family:"Tahoma","sans-serif";color:#1f497d">I set up OpenStack in multi Nodes model, with ML2 Plugin and GRE mode.<u></u><u></u></span></p>
<p><u></u><span style="font-size:11.0pt;font-family:"Tahoma","sans-serif";color:#1f497d"><span>2.<span style="font:7.0pt "Times New Roman""> </span></span></span><u></u><span style="font-size:11.0pt;font-family:"Tahoma","sans-serif";color:#1f497d">I created 2 VMs in the same Compute node. (1 Web and 1 DB).<u></u><u></u></span></p>
<p><u></u><span style="font-size:11.0pt;font-family:"Tahoma","sans-serif";color:#1f497d"><span>3.<span style="font:7.0pt "Times New Roman""> </span></span></span><u></u><span style="font-size:11.0pt;font-family:"Tahoma","sans-serif";color:#1f497d">My App needs fully support packet 1500 Bytes.<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Tahoma","sans-serif";color:#1f497d"><u></u> <u></u></span></p><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Tahoma","sans-serif";color:#1f497d">How can I configure Openstack to do that?<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Tahoma","sans-serif";color:#1f497d"><u></u> <u></u></span></p><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Tahoma","sans-serif";color:#1f497d">----<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Tahoma","sans-serif";color:#1f497d">I already configured:<u></u><u></u></span></p><p><u></u><span style="font-size:11.0pt;font-family:"Tahoma","sans-serif";color:#1f497d"><span>1.<span style="font:7.0pt "Times New Roman""> </span></span></span><u></u><span style="font-size:11.0pt;font-family:"Tahoma","sans-serif";color:#1f497d">Set MTU of Ethernet_interface in VM <u></u><u></u></span></p>
<table border="0" cellspacing="0" cellpadding="0" style="margin-left:36.0pt;border-collapse:collapse"><tbody><tr><td width="312" valign="top" style="width:233.75pt;border:solid windowtext 1.0pt;padding:0cm 5.4pt 0cm 5.4pt">
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Tahoma","sans-serif";color:#1f497d"><u></u> <u></u></span></p><p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:#1f497d">VM1# ifconfig eth0 mtu 1600<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:#1f497d">VM2# ifconfig eth0 mtu 1600<u></u><u></u></span></p><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Tahoma","sans-serif";color:#1f497d"><u></u> <u></u></span></p>
</td><td width="708" valign="top" style="width:530.75pt;border:solid windowtext 1.0pt;border-left:none;padding:0cm 5.4pt 0cm 5.4pt"><p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Courier New";color:#1f497d">root@cuong-vm-01:~# netstat -i<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Courier New";color:#1f497d">Kernel Interface table<u></u><u></u></span></p><p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Courier New";color:#1f497d">Iface MTU Met RX-OK RX-ERR RX-DRP RX-OVR TX-OK TX-ERR TX-DRP TX-OVR Flg<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Courier New";color:#1f497d">eth0 1600 0 15958 0 0 0 10317 0 0 0 BMRU<u></u><u></u></span></p><div style="border:none;border-bottom:solid windowtext 1.0pt;padding:0cm 0cm 1.0pt 0cm">
<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Courier New";color:#1f497d">lo 65536 0 0 0 0 0 0 0 0 0 LRU<u></u><u></u></span></p></div><p class="MsoNormal">
<span style="font-size:9.0pt;font-family:"Courier New";color:#1f497d">root@cuong-vm-02:~# netstat -i<u></u><u></u></span></p><p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Courier New";color:#1f497d">Kernel Interface table<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Courier New";color:#1f497d">Iface MTU Met RX-OK RX-ERR RX-DRP RX-OVR TX-OK TX-ERR TX-DRP TX-OVR Flg<u></u><u></u></span></p><p class="MsoNormal">
<span style="font-size:9.0pt;font-family:"Courier New";color:#1f497d">eth0 1600 0 15936 0 0 0 10009 0 0 0 BMRU<u></u><u></u></span></p><p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Courier New";color:#1f497d">lo 65536 0 0 0 0 0 0 0 0 0 LRU</span><span style="font-size:11.0pt;font-family:"Tahoma","sans-serif";color:#1f497d"><u></u><u></u></span></p>
</td></tr></tbody></table><p class="MsoNormal" style="margin-left:72.0pt"><span style="font-size:11.0pt;font-family:"Tahoma","sans-serif";color:#1f497d"><u></u> <u></u></span></p><p><u></u><span style="font-size:11.0pt;font-family:"Tahoma","sans-serif";color:#1f497d"><span>2.<span style="font:7.0pt "Times New Roman""> </span></span></span><u></u><span style="font-size:11.0pt;font-family:"Tahoma","sans-serif";color:#1f497d">Set MTU of every port in BR-INT to 1600Bytes<u></u><u></u></span></p>
<table border="0" cellspacing="0" cellpadding="0" style="margin-left:38.6pt;border-collapse:collapse"><tbody><tr><td width="926" valign="top" style="width:694.2pt;border:solid windowtext 1.0pt;padding:0cm 5.4pt 0cm 5.4pt">
<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Courier New";color:#1f497d">root@controller:~# netstat -i<u></u><u></u></span></p><p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Courier New";color:#1f497d">Kernel Interface table<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Courier New";color:#1f497d">Iface MTU Met RX-OK RX-ERR RX-DRP RX-OVR TX-OK TX-ERR TX-DRP TX-OVR Flg<u></u><u></u></span></p><p class="MsoNormal">
<span style="font-size:9.0pt;font-family:"Courier New";color:#1f497d">br-ex 1500 0 21680 0 0 0 2928 0 0 0 BRU<u></u><u></u></span></p><p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Courier New";color:#1f497d">br-int </span><span style="font-size:9.0pt;font-family:"Courier New";color:red">1600 </span><span style="font-size:9.0pt;font-family:"Courier New";color:#1f497d">0 308 0 0 0 6 0 0 0 BRU<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Courier New";color:#1f497d">br-tun 1500 0 0 0 0 0 6 0 0 0 BRU<u></u><u></u></span></p><p class="MsoNormal">
<span style="font-size:9.0pt;font-family:"Courier New";color:#1f497d">eth0 1500 0 483582 0 2 0 22859 0 0 0 BMPRU<u></u><u></u></span></p><p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Courier New";color:#1f497d">eth1 1500 0 220 0 0 0 6 0 0 0 BMRU<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Courier New";color:#1f497d">lo 65536 0 174389 0 0 0 174389 0 0 0 LRU<u></u><u></u></span></p><p class="MsoNormal">
<span style="font-size:9.0pt;font-family:"Courier New";color:#1f497d">qbr480003c8-57 1500 0 29 0 0 0 6 0 0 0 BMRU<u></u><u></u></span></p><p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Courier New";color:#1f497d">qbr59db81a4-93 1500 0 46 0 0 0 6 0 0 0 BMRU<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Courier New";color:#1f497d">qvb480003c8-57 1500 0 15907 0 0 0 9877 0 0 0 BMPRU<u></u><u></u></span></p><p class="MsoNormal">
<span style="font-size:9.0pt;font-family:"Courier New";color:#1f497d">qvb59db81a4-93 1500 0 15773 0 0 0 10087 0 0 0 BMPRU<u></u><u></u></span></p><p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Courier New";color:#1f497d">qvo480003c8-57 </span><span style="font-size:9.0pt;font-family:"Courier New";color:red">1600 </span><span style="font-size:9.0pt;font-family:"Courier New";color:#1f497d">0 9877 0 0 0 15907 0 0 0 BMPRU<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Courier New";color:#1f497d">qvo59db81a4-93 </span><span style="font-size:9.0pt;font-family:"Courier New";color:red">1600 </span><span style="font-size:9.0pt;font-family:"Courier New";color:#1f497d">0 10087 0 0 0 15773 0 0 0 BMPRU<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Courier New";color:#1f497d">tap480003c8-57 1500 0 9995 0 0 0 15912 0 0 0 BMRU<u></u><u></u></span></p><p class="MsoNormal">
<span style="font-size:9.0pt;font-family:"Courier New";color:#1f497d">tap59db81a4-93 1500 0 10169 0 0 0 15764 0 0 0 BMRU<u></u><u></u></span></p><p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Courier New";color:#1f497d">virbr0 1500 0 0 0 0 0 0 0 0 0 BMU</span><span style="font-size:11.0pt;font-family:"Tahoma","sans-serif";color:#1f497d"><u></u><u></u></span></p>
</td></tr></tbody></table><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Tahoma","sans-serif";color:#1f497d"><u></u> <u></u></span></p><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Tahoma","sans-serif";color:red">However, I clouldn’t ping from VM 01 to VM02 without fragment<u></u><u></u></span></p>
<p class="MsoNormal" style="margin-left:36.0pt"><span style="font-size:10.0pt;font-family:"Courier New";color:red">root@cuong-vm-01:~# traceroute --mtu 172.16.10.13 <u></u><u></u></span></p><p class="MsoNormal" style="margin-left:36.0pt">
<span style="font-size:10.0pt;font-family:"Courier New";color:red">traceroute to 172.16.10.13 (172.16.10.13), 30 hops max, 65000 byte packets<u></u><u></u></span></p><p class="MsoNormal" style="margin-left:36.0pt">
<span style="font-size:10.0pt;font-family:"Courier New";color:red">1 * F=1600 * *<u></u><u></u></span></p><p class="MsoNormal" style="margin-left:36.0pt"><span style="font-size:10.0pt;font-family:"Courier New";color:red">2 * * *<u></u><u></u></span></p>
<p class="MsoNormal" style="margin-left:36.0pt"><span style="font-size:10.0pt;font-family:"Courier New";color:red">3 * * *<u></u><u></u></span></p><p class="MsoNormal" style="margin-left:36.0pt"><span style="font-size:10.0pt;font-family:"Courier New";color:red">4 * *^C<u></u><u></u></span></p>
<p class="MsoNormal" style="margin-left:36.0pt"><span style="font-size:10.0pt;font-family:"Courier New";color:red">--- <u></u><u></u></span></p><p class="MsoNormal" style="margin-left:36.0pt"><span style="font-size:10.0pt;font-family:"Courier New";color:red">root@cuong-vm-02:~# ping -s 1500 -M do 172.16.10.12<u></u><u></u></span></p>
<p class="MsoNormal" style="margin-left:36.0pt"><span style="font-size:10.0pt;font-family:"Courier New";color:red">PING 172.16.10.12 (172.16.10.12) 1500(1528) bytes of data.<u></u><u></u></span></p><p class="MsoNormal">
<span style="font-size:10.0pt;font-family:"Courier New";color:red"><u></u> <u></u></span></p><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Tahoma","sans-serif";color:red">Thank you very much.<u></u><u></u></span></p>
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