"Supposedly" it should be set for 576 for internet dial up, not 1500. Thanks!

I can tell you ethernet is done like this:

ifconfig etho mtu 576

I rarely use it though. I almost always use my dial up connection, which is shows up as Ethernet:modem0(active) while online.

Look in /etc/ppp/options

Tells you about MRU /MTU settings, but not for dial up.
This is my current active options.

linux:~ # grep -v ^# /etc/ppp/options | grep -v ^$
noipdefault
noauth
crtscts
lock
modem
asyncmap 0
nodetach
lcp-echo-interval 30
lcp-echo-failure 4
lcp-max-configure 60
lcp-restart 2
idle 600
noipx
file /etc/ppp/filters


Does this all look ok? Also, How do I add the MTU setting of 576 to this active option list? Do you suggest another setting for a dial up connection? Since its not listed here, does that mean the computer will just use the 1500 as default? I'm just trying to make sure that I'm set up properly for my dial up connection.

There is a line that says mtu=1492 and mru=1492
change this.