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Okay, here is a real stumper.
One of our POPs can not send microsoft word or excel attachments through our
mailserver. It times out and hangs. We can send any other kind of
attachment through just fine, and we can dial into other POPs and send those
same word and excel attachments through the same mail server.
We are running LVS_NAT, I wouldn't even suspect LVS, but I got a weird
tcpdump while trying to diagnose the problem. We have replaced the router
at the POP and we are showing no errors on it's T1s, or any other sign of
problems at the POP.
The SMTP port is actually running on port 925 on the realservers and LVS
forwards from port 25 on the director to port 925 on the realservers. The
reason I'm posting here is because you can see at the end of the tcpdump,
you can see ACKs being sent through the director on port 925. So it seems
that the NAT translation stops and the realserver is now talking directly to
the client and not getting it's packets translated.
It seems that this starts happening in the middle of the word attachment.
13:58:13.579110 dial-216-198-97-37.triconet.org.1448 >
director.trueband.net.smtp: S 2869415996:2869415996(0) win 8760 <mss
1460,nop,nop,sackOK> (DF)
13:58:13.579481 director.trueband.net.smtp >
dial-216-198-97-37.triconet.org.1448: S 1326594950:1326594950(0) ack
2869415997 win 5840 <mss 1460,nop,nop,sackOK> (DF)
13:58:13.872487 dial-216-198-97-37.triconet.org.1448 >
director.trueband.net.smtp: . ack 1 win 8760 (DF)
13:58:13.908295 director.trueband.net.smtp >
dial-216-198-97-37.triconet.org.1448: P 1:60(59) ack 1 win 5840 (DF)
13:58:14.171444 dial-216-198-97-37.triconet.org.1448 >
director.trueband.net.smtp: P 1:17(16) ack 60 win 8701 (DF)
13:58:14.171625 director.trueband.net.smtp >
dial-216-198-97-37.triconet.org.1448: . ack 17 win 5840 (DF)
13:58:14.171712 director.trueband.net.smtp >
dial-216-198-97-37.triconet.org.1448: P 60:113(53) ack 17 win 5840 (DF)
13:58:14.470326 dial-216-198-97-37.triconet.org.1448 >
director.trueband.net.smtp: P 17:52(35) ack 113 win 8648 (DF)
13:58:14.470585 director.trueband.net.smtp >
dial-216-198-97-37.triconet.org.1448: P 113:121(8) ack 52 win 5840 (DF)
13:58:14.722056 dial-216-198-97-37.triconet.org.1448 >
director.trueband.net.smtp: P 52:81(29) ack 121 win 8640 (DF)
13:58:14.722309 director.trueband.net.smtp >
dial-216-198-97-37.triconet.org.1448: P 121:129(8) ack 81 win 5840 (DF)
13:58:14.978556 dial-216-198-97-37.triconet.org.1448 >
director.trueband.net.smtp: P 81:87(6) ack 129 win 8632 (DF)
13:58:14.979444 director.trueband.net.smtp >
dial-216-198-97-37.triconet.org.1448: P 129:143(14) ack 87 win 5840 (DF)
13:58:15.651127 dial-216-198-97-37.triconet.org.1448 >
director.trueband.net.smtp: . 87:1547(1460) ack 143 win 8618 (DF)
13:58:15.651564 director.trueband.net.smtp >
dial-216-198-97-37.triconet.org.1448: . ack 1547 win 8760 (DF)
13:58:26.453849 director.trueband.net.925 >
dial-216-198-97-37.triconet.org.1417: FP 0:22(22) ack 1 win 8760 (DF)
13:58:44.891684 director.trueband.net.925 >
dial-216-198-97-37.triconet.org.1415: FP 4219030021:4219030043(22) ack
2539552954 win 8760 (DF)
13:59:08.696151 director.trueband.net.925 >
dial-216-198-97-37.triconet.org.1417: FP 0:22(22) ack 1 win 8760 (DF)
14:00:33.180674 director.trueband.net.925 >
dial-216-198-97-37.triconet.org.1417: FP 0:22(22) ack 1 win 8760 (DF)
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