We have a 9509 at the HQ site and a 9216 in the DR site connected via a DS3.
There are periodic times when the fcip link will flap and come back up, sometimes it will continue for minutes and has happened for several hours with this error:
%PORT-5-IF_DOWN_TCP_MAX_RETRANSMIT: %$VSAN 50%$ Interface fcip1 is down(TCP conn. closed - retransmit failure).
My manager is telling me it is a setting on the FCIP profile and it is impossible the DS3 could be congested because it is a point to point link.
Verizon is also telling me it is a Cisco problem having to do with fragmentation.
Originally the fcip profile was configured for 1000 max bandwidth and it was suggested to change it to something closer to the DS3 and this change was made:
fcip profile 1
ip address 10.1.2.1
tcp max-bandwidth-mbps 41 min-available-bandwidth-mbps 30 round-trip-time-ms 4
tcp send-buffer-size 5000
It made no difference at all. There is connectivity to the DR site during the flapping, I can see the bandwidth spike up, but there should be plenty to handle the load during the flapping.
The time I had this problem the serial interface of the DS3 was showing the tx load 65/255 and rx was 5/255.
No interface errors, but I have seen the ping response times go from 3ms to 25ms during this time, an indication of congestion somewhere.
There are no errors on any of the interfaces for the DS3 or the fcip.
I have tried numerous different profile settings and nothing has made a differnce.
I have opened a TAC case and Cisco could find no reason for the flapping and suggested a carrier issue.
Does anyone have any ideas?
Any suggestion would be appreciated.