The MPLS-OPS Archive

[Eric Osborne <eosborne@cisco.com>]

On Tue, Feb 27, 2001 at 08:11:44PM -0800, Mark S. Lewis wrote:
> Right, I'm familiar with the explicit-path feature. This is close to
> what we need. The problem we see is that such explicit path nodes
> (at least the first) must be RouterIDs which are known in the IOS
> mpls traffic-engineering topology.  It doesn't seem possible to
> specify a explicit path independently of the TE topology. Specifying
> a tunnel destination of any IP address other than a known RouterID
> in the topology results in the PCALC failure and does not attempt
> RSVP to establish a path.

The nodes in the path-option don't have to be Router IDs, but they do
have to be in the TE topo DB.

>  We would like to be able to specify an explicit path to any IP
> routeable address which is not in the TE topology database. I'm
> looking for a way to disable the constrained path LSP
> calculation. Is this possible with IOS? If so, how?

out of curiosity, why?  are you trying to get around the single-area
limitation?



eric

> Thanks.
> 
> ... Mark
> 
> http://MapleOptical.com <<<==---- Internet at the speed of light
> 
> Eric Osborne wrote:
> > 
> > On Tue, Feb 27, 2001 at 08:14:57PM -0500, Dave Curado wrote:
> > > > 4. I'm told Juniper supports the ability to manually configure MPLS
> > > > paths (i.e. not rely on TE with OSPF or ISIS). Is this what they refer
> > > > to as "explicit-path LSPs" where they disable constrained path
> > > > computation?
> > >
> > > Both cisco and juniper allow you to set up dynamic paths and/or explicit paths.
> > > You can set up a primary, secondary, tertiary, etc. path, each identified
> > > as dynamic or explicit paths.
> > >
> > > I believe that JunOS will allow you to define various degrees of explicit-ness.
> > > For example, set up an LSP from NY to LA, but go through Dallas
> > > on the way.  Or set up an LSP from NY to LA, but use only green
> > > links, and go through Chicago and Sunnyvale on the way.
> > > Or, build the LSP through this explicit list of LSRs: NYC,
> > > Chicago, Denver, Sunnyvale, and end in LA.
> > > Or even do any of the above, in a given order of preference.
> > 
> > We do something that sounds pretty close, if not identical, to this.
> > You can have different path-options, in whatever order you want.
> > And not only can you specify explicit hops (as seen below), but on
> > really recent code (maybe not out yet; Use the Question Mark), you can
> > do
> > 
> > gsr10(cfg-ip-expl-path)#exclude-address ?
> >   WORD  Enter IP address (A.B.C.D)
> > 
> > this is used in an explicit path to exclude a particular link or node
> > address from path calculation.  Note that you canot use next-address
> > and exclude-address in the same path-option.
> > 
> > >
> > > > 5. Does Cisco IOS support similar explicit-path LSPs?  If so, how does
> > > > one configure it?
> > >
> > > Yes, you can.  You manually define an ERO for the signalling
> > > protocol to use when setting up the LSP.
> > >
> > > ip explicit-path name hoopie-doopie enable
> > >  next-address 192.168.0.1
> > >  next-address 192.168.0.2
> > >  next-address 192.168.0.10
> > >  next-address 192.168.0.11
> > >
> > > interface Tunnel1
> > >  description the blue tunnel
> > >  ip unnumbered Loopback0
> > >  tunnel destination 192.168.0.3
> > >  tunnel mode mpls traffic-eng
> > >  tunnel mpls traffic-eng autoroute announce
> > >  tunnel mpls traffic-eng path-option 1 explicit name hoopie-doopie
> > >
> > > You could add further path-option statements to set up secondary
> > > LSPs, tertiary, etc.  I believe the recommendation is that you
> > > should make the last path-option "dynamic", so that if none of
> > > your preferred paths are available, that the LSP will follow
> > > the IGP.
> > 
> > Yes, that's the recommendation.
> > 
> > eric

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