Change MTU settings on Solaris 5.9

[hpalmer () comsquared com]

Recently a customer of ours has been having an issue w/ remote login from mulitiple customers on there network.  Our 
company installed, configured and setup A Sun Fire V250. The issue, there NetAdmin states, "Our customers are not able 
to login to your /our Sun Box because the MTU is at the default setting of 1500 and needs to be 1480 or 1460."  This  I 
(System Database Admin) believe is totally wrong.  But to prove a point I would like to check the current settings and 
make changes if needed.  
I read some where before that the changes could be made in /etc/networks/interfaces, but not able to locate that 
directory...

any suggestions?

Do or do not, there is no try. -Yoda.