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Transparent Bridging over X.25 and BVI Interface (IRB)

Hi together,

we have a problem with an IRB Configuration via an X.25 Network.

I shortly explain what we have done:

We have 2 Routers (Router A and Router B) connected via X.25 pt-2-pt Subinterfaces. At Router B we have the IRB Feature activated and we have configured an BVI interface that is linked to the X.25 Subinterface. At Router A we have connected an PC to the LAN Interface and the Router should only bridge (IP Traffic) incomming packets from the LAN Interface (fe0/0.55). to the outgoing serial interface (s0/0.55).

The PC (mac 0010.5afb.36cb ) that is connected on e0/0 at Router A has the remote IP Address (192.168.90.33) from the BVI 1 Interface on Router B.

This sounds a little bit crazy but we need this scenario for Management reasons.

With this X.25 encapsulation it is not working (Try to ping from the PC to the BVI Interface). But if we change the encapsulation of serial leased Lines to ppp or Cisco HDLC than it works fine.

Here are extracts from the X25. configs:

Router A:

interface FastEthernet0/0

no ip address

bridge-group 55

bridge-group 55 spanning-disabled

!

interface Serial0/0

bandwidth 512

no ip address

encapsulation x25

no ip route-cache

no ip mroute-cache

x25 address 67890

x25 htc 100

x25 win 7

x25 wout 7

x25 nvc 8

no cdp enable

lapb N1 2104

!

interface Serial0/0.55 point-to-point

no ip route-cache

x25 map bridge 12345 broadcast

bridge-group 55

bridge-group 55 spanning-disabled

!

bridge 55 protocol ieee

bridge 55 route ip

Router B:

bridge irb

bridge 1 protocol ieee

bridge 1 route ip

!

interface BVI1

ip address 192.168.90.34 255.255.255.252

!

interface Serial0

no ip address

encapsulation x25 dce

no ip route-cache

no ip mroute-cache

bandwidth 512

x25 address 12345

x25 htc 100

x25 win 7

x25 wout 7

clockrate 250000

no cdp enable

lapb N1 2104

!

interface Serial0.1 point-to-point

no ip route-cache

x25 map bridge 67890 broadcast

bridge-group 1

bridge-group 1 spanning-disabled

The X.25 vc is up and running. We also see that the packets are bridged over the Link. See output of "sh bridge" command.

Router-B#sh bridge

Total of 300 station blocks, 298 free

Codes: P - permanent, S - self

Bridge Group 1:

Address Action Interface Age RX count TX count

0010.5afb.36cb forward Serial0.1 0 1809 0

What could be the reason that it will not work with X.25 encapsulation ? Could it be a an problem with the address resolution or an IOS Bug?

I think that the Router B maybe can not deencapsulate the packet from the X.25 frame because in the the X.25 frame is no information of the next Layer (Ethernet V2 Frame) or packet that is carrierd in the frame.

With an WAN Analyzer we recognized that both PPP and HDLC (which both worked) have Informations about the packet (802.3) that is carried in the Frame.

1 REPLY
Bronze

Re: Transparent Bridging over X.25 and BVI Interface (IRB)

I suspect that IRB over X25 is just not supported although I could not find it documented anywhere. I know that it definately is not supported over ISDN although I don't believe that is documented either.

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