From: Godswill Oletu (oletu@inbox.lv)
Date: Sun Apr 30 2006 - 20:53:30 GMT-3
Luis,
Though R1 is the hub of the Frame Relay setup in your example, your
configuration did not indicate that R2 is communicating with R3 via R1 and
vice versa.
Do not forget that, All three routers communicates with the Frame Relay
Switch, which then switches the packets among them. So, packets encapsulated
in R2 and destined to R3 do not get de-encapsulated until they get to R3 and
vice versa.
Because, it is not visible, it is easy to forget that something else behind
the scene does the frame relay switching and that these Routers are not
nicely and directly connected as the wonderful and colorful diagrams given
to us by the various lab vendors.
HTH
Godswill Oletu
----- Original Message -----
From: "Luis Rueda" <luis.rueda@comsat.com.co>
To: "CCIE 4 Me" <ccie4me@inbox.lv>; <ccielab@groupstudy.com>
Sent: Sunday, April 30, 2006 6:29 PM
Subject: RE: FRAME-RELAY ENCAPSULATION QUESTION
> Godswill,
>
> What I'm trying to understand is, what happens if this situation appears
> at the CCIE lab, most likely if the encapsulation per dlci mapping is
> not done correctly, you will loose the points for the setting up of the
> frame-relay cloud, don't you think so ? The question is.... Since R2 is
> communication with R3 through R1, does R1 de-encapsulate packets and
> then encapsulate them again ? If this is the case, R2 - R1 mapping
> should be done with cisco's encapsulation and only the mapping towards
> R3 should be done with ietf. If R1 just switches (layer2) packets, then
> you have to correctly configure the encapsulation for every packet sent
> to R3 on R2 (this means put the ietf at the end of the frame-relay map
> on R2 for R3's ip address.
>
> So which one will be ? 1st or 2nd option ?
>
> Regards,
>
> Luis
>
> -----Mensaje original-----
> De: CCIE 4 Me [mailto:ccie4me@inbox.lv]
> Enviado el: Sunday, April 30, 2006 5:24 PM
> Para: Luis Rueda; ccielab@groupstudy.com
> Asunto: Re: FRAME-RELAY ENCAPSULATION QUESTION
>
> Luis,
>
> I am trying hard to understand what you are looking to achieve here.
>
> A Cisco Router will understand both IETF and Cisco encapsulation, it
> will not make any different what encapsulation, you are using to send
> the frame packets to it.
>
> However, if the other end is non-Cisco, then you have to use IETF for it
> to understand what your Cisco Router is sending, on the flip side, your
> Cisco router will understand what the non-cisco router is sending to it,
> because it can de-encapsulate IETF packets, but the frame relay link
> will not come up, because a complete bidirectional handshake have not be
> taken place.
>
> In these days of autosensing, if there is no restriction or requirement
> indicating otherwise, 'encapsulation frame-relay' is enough and if you
> are required to do manual mapping or exclude 'Inverse-ARP, 'frame relay
> map ip n.n.n.n <dlci> broadcast' will be good enough.
>
> Both options you stated below should work fine on a Cisco plateform.
>
> HTH
> Godswill Oletu
>
>
> ----- Original Message -----
> From: "Luis Rueda" <luis.rueda@comsat.com.co>
> To: <ccielab@groupstudy.com>
> Sent: Sunday, April 30, 2006 2:24 PM
> Subject: FRAME-RELAY ENCAPSULATION QUESTION
>
>
> > Hi all,
> >
> > I have a question for the following scenario, let's say we have 3
> > routers, R1, R2, R3.
> >
> > The following topology is used (Hub-Spoke) R1 is the hub, and R2 and
> R3
> > area spokes. If R3 is set with the following config:
> >
> > Interface serial0/0
> > encapsulation frame-relay ietf
> >
> > How should I configure R2 and R1 with frame-relay map statements in
> > order to match the correct encapsulation for R3 ?
> >
> > Should I set the following config:
> >
> > R1 (HUB)
> > Interface serial0/0
> > encapsulation frame-relay
> > ip address 200.200.200.1 255.255.255.0
> > frame-relay map ip 200.200.200.3 103 broadcast ietf
> > frame-relay map ip 200.200.200.2 102 broadcast
> >
> > R2 (SPOKE -CISCO ENCAPSULATION-)
> > Interface serial0/0
> > encapsulation frame-relay
> > ip address 200.200.200.2 255.255.255.0
> > frame-relay map ip 200.200.200.1 201 broadcast
> > frame-relay map ip 200.200.200.3 201 broadcast
> >
> > R3 (SPOKE -IETF ENCAPSULATION-)
> > Interface serial0/0
> > encapsulation frame-relay IETF
> > ip address 200.200.200.3 255.255.255.0
> > frame-relay map ip 200.200.200.1 301 broadcast
> > frame-relay map ip 200.200.200.2 301 broadcast
> >
> > Or should I set it up this way:
> >
> > R1 (HUB)
> > Interface serial0/0
> > encapsulation frame-relay
> > ip address 200.200.200.1 255.255.255.0
> > frame-relay map ip 200.200.200.3 103 broadcast ietf
> > frame-relay map ip 200.200.200.2 102 broadcast
> >
> > R2 (SPOKE -CISCO ENCAPSULATION-)
> > Interface serial0/0
> > encapsulation frame-relay
> > ip address 200.200.200.2 255.255.255.0
> > frame-relay map ip 200.200.200.1 201 broadcast
> > frame-relay map ip 200.200.200.3 201 broadcast ietf
> >
> > R3 (SPOKE -IETF ENCAPSULATION-)
> > Interface serial0/0
> > encapsulation frame-relay IETF
> > ip address 200.200.200.3 255.255.255.0
> > frame-relay map ip 200.200.200.1 301 broadcast
> > frame-relay map ip 200.200.200.2 301 broadcast
> >
> > Regards,
> >
> > Luis
> >
> >
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