routes and netmasks

Igor V. Semenyuk (iga@sovam.com)
Fri, 6 Oct 1995 03:48:21 +0300 (MMT)

Is the host route to host 0 legal? For example, is 192.0.0.0/32 legal?

I ask this question because Livingston allows to create such routes
easiely:

1) add route 192.0.0.0 some.gate.way 1

All 192.0.0.x traffic goes to some.gate.way

2) add netmask 192.0.0.0 255.255.255.255

All 192.0.0.x traffic goes via default gateway (perhaps
traffic to host 192.0.0.0 would go to some.gate.way but
I never tried this)

And now a trick:

3) add route 192.0.0.0 some.gate.way 1

Oops, now I have two routes to 192.0.0.0 which appear
identical on 'show route' display, but are different
internally. It seems that ComOS stores the current value
of netmask for the network along with the route itself.
Wouldn't it be more logical to display the netmask in
'show route' output? And get rid of add/del netmask commands?

Unfortunately this behavior prevents from installing a 'black hole'
BTW cisco replies with 'Inconsistent address and mask' when you try
'ip route 192.0.0.0 255.255.255.255 a.b.c.d'.

-- 
Igor V. Semenyuk                    Internet: iga@sovam.com
SOVAM Teleport                      Phone:    +7 095 258 4170
Moscow, Russia                      Fax:      +7 095 258 4133