Re: DHCP and secondaries

[Richard Letts <[e-mail]>]

Mike Carney - Sun BOS Software wrote....
> 
> I'm curious - Are you subnetting Class B networks to class C, and find that 
> 254 addresses is not enough for one media segment, or do you have a number 
> of Class C addresses, and must use multiple logical networks on the same 
> media the service the number of hosts you've got out there?
> 
The campus network hert is *very* routed. with an average of 40 hosts/subnet
we have a 'normal' subnet mask of 255.255.255.128

some networks have grown more than they were supposed to, and we have had to
expand the subnet range on the cable; in general this is by either changing
the subnet mask for the hosts on the cable, or in the first instance making
the next address-range on the cable the primary and the existing rang the
secondary.

eg.  146.87.253.0 ran out of addresses.

1. make 146.87.253.0 the secondary network number on the router
2. make 146.87.253.128 the primary network number on the router
3. change the subnet mask to be 255.255.255.0 on other devices on the network
4. wait until everthing agrees what the subnet-mask is now
5. make 146.87.253.0/255.255.255.0 the network/mask for the network on the
router.

[I tell departments not to use the .128 networks in their initial setup to
allow them flexibility to do this later]

Of course this falls-down when you come across a host that doesn't
understand subnetworks (we still have some this stupid), then it has
to go somewhere proxy-arp is supported.

As the network topology is getting flattened we're ending up with multiple
networks on the same cable that have no relationship; in this case we tell
everything that the mask is 255.255.0.0, and rely on proxy-arp.

Richard Letts  
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