Conference netcad::hub_mgnt

847.0. "SUBNET MASK PB with POLYCENTER NETVIEW" by MARS03::THOMAS () Tue Mar 22 1994 05:36

	On a customer site, i use POLYCENTER MANAGER on NETVIEW (SSB kit) to
manage an IP network.

	 On this IP network and on the same ETHERNET LAN, there are the PNV
station and a DEChub 900. The subnet of this LAN is 145.42.41 with 255.255.255.0
for the subnet mask.

	The IP address of the PNV station is 145.42.41.4 with a subnet mask of 
255.255.255.0.
	The IP address of the DEChub 900 is 145.42.41.5 without subnet mask. The
DEChub 900 doesn't support subnet mask.

	With this configuration, PNV finds all the subnets 145.42.40, 145.42.41,
145.42.50 ... But, it finds the 145.42 subnet that doesn't exist.

	How can i fix this problem because this virtual subnet disturbs NETMON
daemon ?


	I put this note in the HUB_MGNT and in the NETVIEW conferences.


	Thanks for any information.

	Regards


	Bernard THOMAS

[Also posted in IMDOWN::NETVIEW Note 313.6]
    
    It is true that the DEChub 900 (and most of the DEChub family of
    products) do not support configuration of subnet mask.  This is because
    they almost never have needed to send unsolicited messages.  When they
    don't have an entry in thier address cache for an IP address, they send
    to the default gateway and let it correct them with an ICMP redirect if
    the station is actually local.
    
    This shortcut seems to be the ultimate cause of your problem, since
    they do reflect the subnet value in MIB-II based on the address class. 
    
    I can't help with workarounds for the problem this causes with PNV;
    further discussion of the merits (or lack thereof) of the approach
    should take place here.