From: ccie2be (ccie2be@nyc.rr.com)
Date: Thu Oct 07 2004 - 12:34:07 GMT-3
Brian,
You're the best. Thanks
----- Original Message -----
From: "Brian McGahan" <bmcgahan@internetworkexpert.com>
To: "ccie2be" <ccie2be@nyc.rr.com>; "mani poopal" <mani_ccie@yahoo.com>
Cc: <ccielab@groupstudy.com>
Sent: Thursday, October 07, 2004 9:59 AM
Subject: RE: ospf virtual-links vs GRE
> In terms of functionality, the only difference between a GRE tunnel
and
> virtual link is that with a GRE tunnel the transit area can be of any
type
> (stub, nssa, regular non-backbone area) while with a virtual link the
> transit area must be a regualr non-backbone. Correct?
Yes, but the tunnel adds GRE overhead to all traffic transiting
it.
> With a GRE tunnel, the endpoints must be in and advertised throughout
the
> transit area. They don't have to be physical interfaces. They could
be
> loopback interfaces in the transit area. True?
Any address that the endpoints have reachability to.
> With GRE tunnel, the ip address is arbitrary but must be advertised in
> Area
> 0. True?
Yep.
HTH,
Brian McGahan, CCIE #8593
bmcgahan@internetworkexpert.com
Internetwork Expert, Inc.
http://www.InternetworkExpert.com
Toll Free: 877-224-8987 x 705
Outside US: 775-826-4344 x 705
24/7 Support: http://forum.internetworkexpert.com
Live Chat: http://www.internetworkexpert.com/chat/
> -----Original Message-----
> From: ccie2be [mailto:ccie2be@nyc.rr.com]
> Sent: Thursday, October 07, 2004 6:15 AM
> To: Brian McGahan; mani poopal
> Cc: ccielab@groupstudy.com
> Subject: Re: ospf virtual-links vs GRE
>
> Hi Brian,
>
> That example was very helpful. Thank you.
>
> I'd like to confirm my understanding and summarize some concepts
related
> to
> this topic.
>
> In terms of functionality, the only difference between a GRE tunnel
and
> virtual link is that with a GRE tunnel the transit area can be of any
type
> (stub, nssa, regular non-backbone area) while with a virtual link the
> transit area must be a regualr non-backbone. Correct?
>
> With a GRE tunnel, the endpoints must be in and advertised throughout
the
> transit area. They don't have to be physical interfaces. They could
be
> loopback interfaces in the transit area. True?
>
> With GRE tunnel, the ip address is arbitrary but must be advertised in
> Area
> 0. True?
>
> Thanks, Tim
>
> ----- Original Message -----
> From: "Brian McGahan" <bmcgahan@internetworkexpert.com>
> To: "mani poopal" <mani_ccie@yahoo.com>
> Cc: <ccielab@groupstudy.com>
> Sent: Wednesday, October 06, 2004 8:13 PM
> Subject: RE: ospf virtual-links vs GRE
>
>
> > Mani,
> >
> > Yes, that is exactly what I was referring to. See the following
> > output:
> >
> > R1#show ip ospf int lo0 | in Area
> > Internet Address 10.1.1.1/24, Area 0
> > R1#show ip ospf int tun0 | in Area
> > Internet Address 0.0.0.0/0, Area 0
> > R1#show ip ospf int e0/0 | in Area
> > Internet Address 15.1.1.1/8, Area 1
> >
> > R1#show ip ospf nei
> >
> > Neighbor ID Pri State Dead Time Address
> > Interface
> > 10.2.2.2 0 FULL/ - 00:00:34 10.2.2.2
> > Tunnel0
> > 10.2.2.2 1 FULL/BDR 00:00:33 15.1.1.2
> > Ethernet0/0
> >
> > R2#show ip ospf nei
> >
> > Neighbor ID Pri State Dead Time Address
> > Interface
> > 10.1.1.1 0 FULL/ - 00:00:38 10.1.1.1
> > Tunnel0
> > 10.1.1.1 1 FULL/DR 00:00:38 15.1.1.1
> > Ethernet0/0
> > 3.3.3.3 0 FULL/ - 00:00:34 23.0.0.3
> > Serial0/1
> >
> > R3#show ip ospf nei
> >
> > Neighbor ID Pri State Dead Time Address
> > Interface
> > 10.2.2.2 0 FULL/ - 00:00:35 23.0.0.2
> > Serial1/3
> >
> >
> > R1#sh ip route ospf
> > O IA 23.0.0.0/8 [110/11175] via 10.2.2.2, 00:00:33, Tunnel0
> > 10.0.0.0/8 is variably subnetted, 3 subnets, 2 masks
> > O 10.2.2.2/32 [110/11112] via 10.2.2.2, 00:03:22, Tunnel0
> > O IA 10.3.3.3/32 [110/11176] via 10.2.2.2, 00:00:23, Tunnel0
> >
> > R2#sh ip route ospf
> > 10.0.0.0/8 is variably subnetted, 3 subnets, 2 masks
> > O 10.3.3.3/32 [110/65] via 23.0.0.3, 00:00:19, Serial0/1
> > O 10.1.1.1/32 [110/11112] via 10.1.1.1, 00:00:29, Tunnel0
> >
> > R3#show ip route ospf
> > 10.0.0.0/8 is variably subnetted, 3 subnets, 2 masks
> > O IA 10.2.2.2/32 [110/782] via 23.0.0.2, 00:00:20, Serial1/3
> > O IA 10.1.1.1/32 [110/11893] via 23.0.0.2, 00:00:20, Serial1/3
> > O IA 15.0.0.0/8 [110/791] via 23.0.0.2, 00:00:20, Serial1/3
> >
> >
> >
> > HTH,
> >
> > Brian McGahan, CCIE #8593
> > bmcgahan@internetworkexpert.com
> >
> > Internetwork Expert, Inc.
> > http://www.InternetworkExpert.com
> > Toll Free: 877-224-8987 x 705
> > Outside US: 775-826-4344 x 705
> > 24/7 Support: http://forum.internetworkexpert.com
> > Live Chat: http://www.internetworkexpert.com/chat/
> >
> >
> > > -----Original Message-----
> > > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On
Behalf
> > Of
> > > mani poopal
> > > Sent: Wednesday, October 06, 2004 6:36 PM
> > > To: Brian McGahan
> > > Cc: ccielab@groupstudy.com
> > > Subject: RE: ospf virtual-links vs GRE
> > >
> > > Brian,
> > >
> > > If R1 connect to area 0 & 1. R2 connect to area 1& 2. How can I
make
> > an
> > > unnumbered interface (R2's lo 0 to participate in area 0). Is the
> > > following config should be ok on R2(note I am advertiseing lo 0 of
R2
> > in
> > > area 0 eventhough R2 is not connected to area 0.)
> > >
> > > Example:
> > >
> > > ----------area 0---R1(15.1.1.1)------Area
> > 1--------(15.1.1.2)R2-----Area
> > > 2------R3
> > > R1 lo 0=10.1.1.1/24
> > > R2 lo 0=10.2.2.2/24
> > > R2 lo 0=10.3.3.3/24
> > >
> > > R1 Config:
> > > router ospf 1
> > > network 15.1.1.1 0.0.0.0 area 1
> > > network 10.1.1.1 0.0.0.0 area 0
> > >
> > > int tunnel 0
> > > ip unnumbered lo 0
> > > tunnel source 15.1.1.1
> > > tunnel destination 15.1.1.2
> > >
> > >
> > > R2 Config:
> > > router ospf 1
> > > network 15.1.1.2 0.0.0.0 area 1
> > > network 10.2.2.2 0.0.0.0 area 0<------Since I am using unnumbered
lo 0
> > is
> > > it area 0 or 2
> > >
> > > int tunnel 0
> > > ip unnumbered lo 0
> > > tunnel source 15.1.1.2
> > > tunnel destination 15.1.1.1
> > >
> > > PS:Brian in R2 the loopback is advertised as area 0 or area1.
With
> > the
> > > above config, will I will be able to see R3's routes(lo 0) in R1.
I
> > > haven't tested yet. Thanks for taking your time.
> > >
> > > Mani
> > >
> > >
> > >
> > >
> > > Brian McGahan <bmcgahan@internetworkexpert.com> wrote:
> > > Mani,
> > >
> > > As long as the tunnel sources and destinations are reachable by
> > > both endpoints of the tunnel, the ip address used on the tunnel
itself
> > > is arbitrary, as long as it participates in area 0. Also, you
don't
> > > necessarily even have to give the tunnel it's own address. You
could
> > > unnumber it to another interface that is already participating in
OSPF
> > > area 0.
> > >
> > > Brian McGahan, CCIE #8593
> > > bmcgahan@internetworkexpert.com
> > >
> > > Internetwork Expert, Inc.
> > > http://www.InternetworkExpert.com
> > > Toll Free: 877-224-8987 x 705
> > > Outside US: 775-826-4344 x 705
> > > 24/7 Support: http://forum.internetworkexpert.com
> > > Live Chat: http://www.internetworkexpert.com/chat/
> > >
> > >
> > > > -----Original Message-----
> > > > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On
Behalf
> > > Of
> > > > mani poopal
> > > > Sent: Wednesday, October 06, 2004 1:32 PM
> > > > To: James
> > > > Cc: ccielab@groupstudy.com
> > > > Subject: Re: ospf virtual-links vs GRE
> > > >
> > > > Hi James,
> > > >
> > > > Thanks for the info. From where we are getting ip address for
the
> > > tunnel
> > > > interface(10.1.10.1). Then we are advertising this network in
the
> > > routing
> > > > domain and this route is propaged to the rest of the network. Is
it
> > > ok to
> > > > come up with an ip address for tunnel interface. Because we
> > shouldn't
> > > > learn about the tunnel interface itself from the routing
> > > protocol(ospf),
> > > > do we have to advertise it in a different routing protocol, say
rip.
> > > I am
> > > > looking through cisco website and could not get good config
example
> > > for
> > > > gre/tunnel interface for ospf/rip/eigrp configuration. Any
> > suggestion
> > > > which books or url is better for this subject. By the way I
tried
> > the
> > > > command you gave me and is not working, from both ABR's I
created a
> > > tunnel
> > > > interface and advertised both tunnel interface in area 0.
> > > >
> > > > thanks
> > > >
> > > > Mani
> > > >
> > > > James wrote:
> > > > On Wed, Oct 06, 2004 at 06:36:37AM -0700, mani poopal wrote:
> > > > > Hi Group,
> > > > >
> > > > > In the exam if an ospf area is not connected to area 0, you
can
> > use
> > > > virtual link to have the connectivity. It the requirement says
not
> > to
> > > use
> > > > virtual link, I know you can achieve the desired result by GRE
> > tunnel.
> > > Can
> > > > any one point me to sampe url for configuration in the cisco
website
> > > or
> > > > post a sample config.
> > > >
> > > > Router A:
> > > > in tun0
> > > > tun so a.a.a.a
> > > > tun des b.b.b.b
> > > > ip add 10.1.10.1 255.255.255.252
> > > > no shut
> > > > !
> > > > router osp 100
> > > > net 10.1.10.0 0.0.0.3 ar 0
> > > > !
> > > >
> > > > Router B:
> > > > in tun0
> > > > tun so b.b.b.b
> > > > tun des a.a.a.a
> > > > ip add 10.1.10.2 255.255.255.252
> > > > no shut
> > > > !
> > > > router osp 100
> > > > net 10.1.10.0 0.0.0.3 ar 0
> > > > !
> > > >
> > > > HTH,
> > > > -J
> > > >
> > > >
> > > > --
> > > > James Jun TowardEX Technologies, Inc.
> > > > Technical Lead Network Design, Consulting, IT Outsourcing
> > > > james@towardex.com Boston-based Colocation & Bandwidth Services
> > > > cell: 1(978)-394-2867 web: http://www.towardex.com , noc:
> > www.twdx.net
> > > >
> > > >
> > >
> >
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