Subject: RE: (usr-tc) Static Routing Question

From: Colin Wantling <[email-masked]>
Date: Tue, 25 Apr 2000 20:08:25 +0000

Jeff/Mike,

Maybe yes, maybe no. The route Mike is adding has a /32 mask, he doesn't say
what the mask is on the HARC ethernet interface already.  The mask is very
likely wider than that to provide server IP address space.  All depends what
that existing mask is. 
We are agreed anyway that IP aliasing is a possible alternative. For Mike's
information, IP aliasing is a technique where you give the server more than
one IP address. By giving it an address from another subnet, you can beat
the rules. You also need to create an IP alias on the HARC ethernet
interface by adding a new network to the interface. How it's all done will
depend very much on the type of server type, Unix/NT/Other. Might be a good
idea to take this off-line if we're getting down to details!

Regards,

Colin

	Also sprach Colin Wantling
	>But 10.1.1.9 and 10.1.1.12 are on the same subnet.

	Bah!  Get that classful crap out of your head! :)  The IP address
	10.1.1.12 is most definitely not in 10.1.1.9/32.

	>The Harc gets packets to the local destination using the MAC
address on
	>the local subnet.

	For a directly connected route, yes.  There's no reason that you
	shouldn't be able to have a more specific static route though.

	>IP aliasing might provide a way to do what you want.

	Kludge at best, but until 3Com fixes the code...this is probably how
I
	would pursue it as well.
	-- 
	Jeff McAdams                            Email: [email-masked]
	Head Network Administrator              Voice: (502) 966-3848
	IgLou Internet Services                        (800) 436-4456

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From: Jeff Mcadams <[email-masked]>
Date: Tue, 25 Apr 2000 20:45:29 +0000

>Maybe yes, maybe no. 

No "maybe" to it...as long as the next-hop of the route isn't within the
route itself, there's no problem.  10.1.1.12 isn't within 10.1.1.9/32,
so there's no problem.  Even if it were, its *possible* to even get that
to work...but there's not a "standard" way of doing it.  If you put the
/32 in there, its gonna be the most specific route, so it will (should)
be referenced before any shorter length match.  At that point, the only
questions are, "Is the next-hop reachable?"  There's another route that
is valid for the next-hop address (locally connected), so yes.  "Is
there a higher precedence route of the same mask length (ie, /32)?"
Possible, but unlikely.

>The route Mike is adding has a /32 mask, he doesn't say what the mask
>is on the HARC ethernet interface already.  

Doesn't matter.  As long as the next-hop for the /32 route is reachable,
it should be accepted.  Even if the next-hop isn't reachable, the route
should probably be accepted...just not entered into the active routing
table.

>By giving it an address from another subnet, you can beat
>the rules.

s/rules/bugs/  :)

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