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Conference netcad::hub_mgnt

Title:DEChub/HUBwatch/PROBEwatch CONFERENCE
Notice:Firmware -2, Doc -3, Power -4, HW kits -5, firm load -6&7
Moderator:NETCAD::COLELLADT
Created:Wed Nov 13 1991
Last Modified:Fri Jun 06 1997
Last Successful Update:Fri Jun 06 1997
Number of topics:4455
Total number of notes:16761

2271.0. "Advertising routes through 900EF" by CCOF02::PENNO (Murray Penno) Thu May 11 1995 21:39

Hi,

We have a switching opportunity which is defined as requiring level 2 switching
and level 3 routing.  The requirement for routing is due to the company having
three class network addresses.

I want to use 4 decswitch 900EF in a ring to privide the connections to servers
and users.  The question is how do I include a level of routing in this scenario.

Is it possible to put something like a decbrouter on the network and define all
the ip networks as being on the ethernet interface?  Would this allow users in 
one ip network to communicate with a server on another ip network? Do all
packets that need to go to another ip network have to go through the decbrouter?

Will ip route advertisements go through decswitches?
Hve I missed somthing fundamental here?

I know the 900EF will have routing but this is too far away. 

Any help really appreciated.

Murray
T.RTitleUserPersonal
Name		DateLines
2271.1NETCAD::ANILThu May 11 1995 23:349
    This is basically the "multiple subnets on a wire" scenario.  Yes,
    it should work but is far from optimal for two reasons: you are using
    the Ethernet as a backbone for the FDDI (!), and secondly all packets
    will go through the brouter.  Since the switches are transparent,
    they look like a single Ethernet to the brouter -- you can test whether
    this works simply by setting multiple subnets on the Ethernet of
    the brouter.
    
    Anil
2271.2Watch that subnet mask...NAC::LICAUSESat May 13 1995 21:4917
    I may be off base here, but I think it will really depend to a certain
    extent on how your setup your end systems.  For example, if you setup
    multiple IP subnets on a single router interface and have end systems
    distributed throughout the LAN using different subnet addresses, then
    they may or may not hit the router.
    
    Again, someone please correct me if I'm wrong, but I believe the end
    system will first apply it's mask to both the end system's address
    as well as it's own.  If it finds that both systems are on the same
    LAN, then the router will not be contacted.
    
    For instance, if subnets 16.20.40 and 16.20.41 are on the same LAN and
    routed by the same router, on the same interface, then the use of a
    255.255.0.0 end system mask will allow both end systems to talk w/o
    using the router.  If, however, both end systems use a 255.255.255.0
    mask, then they will always use the router for each and every packet
    they want to send to each other.
2271.3KAOFS::S_HYNDMANRide life's curvesSun May 21 1995 19:0610
    
    
    You can define multiple addresses for the ethernet interface on the
    DB90 and have it route between subnets. The switches will pass all 
    frames.  As stated all packets destined for a different subnet will
    have to go through the DB90.  We have done this while we wait for routing 
    code.  If memory serves, a parameter called split horizions had to be 
    enabled.
    
    Scott
2271.4NETCAD::ANILThu May 25 1995 23:4923
>    Again, someone please correct me if I'm wrong, but I believe the end
>    system will first apply it's mask to both the end system's address
>    as well as it's own.  If it finds that both systems are on the same
>    LAN, then the router will not be contacted.
    
    This is correct.  Since the question was what does it take to
    get some kind of routing going, I was pointing out that all such
    packets must go through the router, which includes not only
    unnecessary extra hops but also congesting the Ethernet to
    which the router was connected.
    
>    For instance, if subnets 16.20.40 and 16.20.41 are on the same LAN and
>    routed by the same router, on the same interface, then the use of a
>    255.255.0.0 end system mask will allow both end systems to talk w/o
>    using the router.  If, however, both end systems use a 255.255.255.0
>    mask, then they will always use the router for each and every packet
>    they want to send to each other.
    
    The subnet mask must of course be set to whatever the proper subnet
    mask is for the IP network, ie this should be the same regardless of
    what routers are being used.
    
    Anil