Frame Relay over ISDN problem

keller.oliver · ‎01-11-2008

Hi all,

in a lab setup, I have two 2611XM connected via ISDN.

Router A (customer) tries to connect to Router B (ISP).

This works fine, as long as I choose encapsulation ppp.

This does not work when I choose encapsulation frame-relay.

Router A (customer) is FR DTE, Router B (ISP) is FR DCE. Using a DLCI of 123, I get a working Frame-Relay connection:

- PVCs are there and active

- frame relay mapping is ok (static, active)

- ping echo requests sent from Router A are seen at router B.

However, when router B tries to answer these request, I get an "encapsulation failed" error on Router B.

As soon as I switch back to ppp, everything works fine, so I guess it's no ISDN-problem.

Thanks in advance,

Oliver

Here are the two configurations :

Router A:

!

interface BRI0/0

ip address 12.0.0.1 255.0.0.0

encapsulation frame-relay

dialer idle-timeout 300

dialer string 20

dialer-group 1

isdn switch-type basic-net3

isdn point-to-point-setup

frame-relay map ip 12.0.0.2 123

frame-relay interface-dlci 123

end

Router B:

!

interface BRI0/0

ip address 12.0.0.2 255.0.0.0

encapsulation frame-relay

dialer idle-timeout 300

isdn switch-type basic-net3

isdn point-to-point-setup

frame-relay map ip 12.0.0.1 123

frame-relay interface-dlci 123

frame-relay intf-type dce

end

owillins · ‎01-17-2008

One reason could be that the Cisco router has attempted to send an IP packet out to an interface that is not connected, or is in the process of connecting. An example is an interface that first needs to dial out, and then connect to a remote router. This is done before it can send any packets. During the dialing and connecting phase, it is normal to receive the encapsulation failed error message.