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

From: Colin Wantling <[email-masked]>
Date: Tue, 25 Apr 2000 21:03:34 +0000

Jeff,

We need Mike to confirm what the mask is on the HARC interface. This will
get us past this techie discussion an onto helping the guy. His attached
network may well be mask /29 /28 ... etc. This would give the error message
he gets as it would then include the address of the HARC itself. Not a
question of Classful/Classless, more a question of inconsistency and getting
caught.

Regards,

Colin

	Also sprach Colin Wantling
	>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/  :)
	-- 
	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 21:20:13 +0000

>We need Mike to confirm what the mask is on the HARC interface. 

Again, what the mask is on the Arc interface doesn't...well, shouldn't
anyway...matter.  

Trying to set up a static route, 10.1.1.9/32 with a next-hop of
10.1.1.12, should pretty much *never* give an error like that.  Now,
depending upon several other factors, it may not actually install the
route into the active routing table, but the system should not give the
error that it did.  In classless routing, there is no problem entering a
route such as that above, even if a less specific route that encompasses
that route is locally connected, the most specific route is chosen,
period.  Whether the route is locally connected or static, or OSPF or
RIP, or whatever, is not relevant at this point.

>His attached network may well be mask /29 /28 ... etc. 

So?  Why should that cause any problem?

>This would give the error message he gets as it would then include the
>address of the HARC itself. Not a question of Classful/Classless, more
>a question of inconsistency and getting caught.

But there is absolutely nothing inconsistent about it.  10.1.1.9/32 ->
10.1.1.12 is perfectly consistent assuming 10.1.1.12 is reachable (which
the earlier discussion indicated it was), even if its not reachable, it
shouldn't generate an error like that, possibly a different error, but
certainly not the one that is given.  Given classless routing, there is
no problem with entering the route that Mike specified.

Again...this is purely an issue of 3Com not allowing perfectly legal,
though less common configurations.  3Com has decided to protect us from
ourselves.

The route table setup that Mike would wish to see (and is perfectly
legal) would look something like:

Network   /Mask    Next-hop            protocol
10.1.1.0  /24      10.1.1.8(eth:0)     local (directly connected)
10.1.1.9  /32      10.1.1.12           static

(went back and looked in previous messages...the Arc is 10.1.1.8 on a /24
netmask)
-- 
Jeff McAdams                            Email: [email-masked]
Head Network Administrator              Voice: (502) 966-3848
IgLou Internet Services                        (800) 436-4456

-