Conference turris::digital_unix

8755.0. "NFS hangs with FDDI network" by KERNEL::CARPENTERS (One inode short of a file system) Fri Feb 07 1997 10:02

 
    A customer of mine has been having a few problems with NFS hangs when
    they use FDDI on their system. This is what they have said and it's a
    bit beyond my networking knowledge:
    
      I had a thought which might possibly have something to do with the
      NFS/FDDI hangs. Since we rebooted for the second time today at 1.20pm
      with tu0 as the primary device, there have been no NFS problems at all.
      In order to prevent NFS attacks from outside the subnet, I configure
      NFS in a somewhat unusual way. The web server uses the IP alias
      163.1.2.16 (in addition to its real IP number) and does *not* respond
      to arp requests on that interface (ifconfig eth0 163.1.2.16 -arp).
      That way, the subnet router cannot possibly send in NFS datagram
      forgeries from outside the subnet (and we secure the machine room
      subnet ourselves). When sable boots, it pings the two possible hosts
      which might be "the" web server (there's a hot spare) and uses
      "arp -s 163.1.2.16 ....." to install a permanent arp entry to the
      appropriate host. I wonder if the FDDI driver is not using the arp
      table correctly: perhaps something is timing out and then never
      consulting it again?
    
    
    Does anyone have any opinions about this?
    
    Stephen.