Subject: Re: static route strangeness
To: Tad Hunt <tad@entrisphere.com>
From: Seth Kurtzberg <seth@cql.com>
List: tech-kern
Date: 10/28/2002 23:59:12
Does anyone know of a document that compares gated to routed?

On Mon, 2002-10-28 at 18:08, Tad Hunt wrote:
> 
> Thanks for the pointer to gated(8).  It does everything I need.  Now
> our software simply has to construct a gated.conf file and say
> "gdc reconfig" whenever it changes.
> 
> The only thing it doesn't handle is the interface MTU changing,
> but it does handle the interface going up and down, so as long as
> I bring the interface down before changing the mtu, all of the
> routes are maintained correctly.
> 
> WHOO!
> 
> -Tad
> 
> In message <B4DFCB7CDE2DD4118F690008C786941604D785A4@tahoe.allegronetworks.com>
> , you said:
> ;3) It sounds like you're looking for a routing daemon. I know, for example,
> ;that GateD properly maintains static routes, and updates them based on
> ;changes to interface. Perhaps zebra also supports static routes in a similar
> ;way.
> ;
> ;I'm not sure if GateD would flush and re-add routes if the only thing that
> ;changed was an interface's MTU.
> ;
> ;Chris.
> ;
> ;-----Original Message-----
> ;From: Tad Hunt [mailto:tad@entrisphere.com]
> ;Sent: Saturday, October 26, 2002 8:29 PM
> ;To: tech-kern@netbsd.org; tech-net@netbsd.org
> ;Subject: static route strangeness
> ;
> ;
> ;
> ;I've recently encountered some problems attempting to maintain a
> ;some static routes.
> ;
> ;Specifically, it appears as though NetBSD computes the interface
> ;and MTU used to reach the gateway at the time the static route is
> ;entered into the routing table.  This information appears to be
> ;stored in the routing table along with the destination, mask, and
> ;gateway (netstat -nr).
> ;
> ;Furthermore, it appears as though bringing a new interface up, or
> ;modifying the MTU of an existing interface doesn't cause any existing
> ;routes to be updated with the new information.
> ;
> ;For example:
> ;
> ;	ifconfig fxp0 192.168.1.1 netmask 0xffffff00 up
> ;
> ;	route add -net 192.168.10.0 192.168.2.2
> ;
> ;	ifconfig fxp1 192.168.2.1 netmask 0xffffff00 up
> ;
> ;After bringing the second interface up, I would have expected the
> ;routing table entry for 192.168.10.2 to become associated with
> ;fxp1.  Instead, netstat(1) shows that it is still associated with
> ;fxp0.
> ;
> ;This behavior makes interface and routing table management extremely
> ;difficult because it effectively requires the routing table to be
> ;flushed and reconstructed every time an interface is brought up or
> ;down, or the MTU changes.
> ;
> ;I believe that the correct behavior is to update the routing table
> ;whenever an interface address, netmask, or MTU is modified.
> ;
> ;I have a some questions:
> ;
> ;1) Is there some way to configure my system such that the routing table
> ;   will automatically be updated?
> ;
> ;2) Is there a specific reason that the routing table behaves the way
> ;   I described, or is this a problem that nobody has attacked yet?
> ;
> ;3) Does anyone have any other suggestions on how to maintain the
> ;   routing table when faced with interface changes over time?
> ;
> ;-Tad
-- 
Seth Kurtzberg
M. I. S. Corp
480-661-1849
Pager 888-605-9296, or 6059296@skytel.com