03-03-2010 07:04 AM
Here's some more info on Dlink from a coworker:
Chuck, the offending rule in the router’s firewall config does a blanket
set of the TCP MSS to 1360. So I'd guess an MTU of less than 1360 should
do it (I am NOT a TCP/IP expert). Alternatively you can telnet to the
router itself and remove the rule:
will show the rule, looks like this:
Chain FORWARD (policy ACCEPT)
target prot opt source destination
TCPMSS tcp -- anywhere anywhere tcp flagsYN,RST/SYN TCPMSS set 1360
To remove it:
iptables -D FORWARD 1
There is quite a bit of discussion on the web about it, "iptables
linkedin Dlink" brings most of it up.
03-03-2010 09:56 AM
Thanks for the clues about MTU. I'll have time later tonight to experiment. Much of the stuff on the web about D-link iptables deals with the D-link routers. My test mini-network has no router in it - only the switch being tested between the PC and BA. I'll try ping tests with varying buffer sizes to see what size causes fragmenting through the switch.
I picked up two Netgear GS608 switches this morning at Compusa with a sweet rebate deal until March 31, but I won't take them out of the shrink-wrap if I can get the D-link switches to work with the BA.
I'll post my results.
03-03-2010 05:47 PM
By pinging the BA with increasing ping buffer sizes, I found the maximum that worked was 1472. Anything bigger fragmented through either the Netgear or D-link switches or directly to the BA from the laptop (with no network) so I didn't learn anything and I'm baffled why the D-link switches don't work anymore.
With my new Netgear switches the BA is fast from any computer on the network. 25+MBps writes and 45+Mbps reads. I tried increasing the BA's MTU from 1500 to 9000 and it slows read and write speeds to about half. Settings between 1500 and 9000 were proportionally slow, so I left the MTU at the default 1500.
I'm chalking this up to a "learning moment" (learning that D-link switches suck) costing me $100 leaving me with gigabit doorstops.
I hope my experience here benefits others searching for answers.