[cisco-bba] About converting from IRB to RBE

[Siva Valliappan]

the range command basically creates a bunch of point-to-point subints.
so in effect you were giving the same ip address to each p2p which
caused the duplicate ip error message.  if you are going to use
the range command, create a loopback interface and assign the ip address
to the loopback interface.  then unnumber the ATM subint to the loopback.

not many choices if you are going to use range or create multiple subints
if you want them to share the same IP.  they have to be unnumbered.
you can unnumber to a loopback (recommended way) or to some other
interface (lan, wan, bvi, etc).  a loopback is better as it's an interface
that is always up.

cheers
.siva


On Wed, 6 Aug 2003, Mark E. Mallett wrote:

> Related to my other message: I had a couple of nit questions about
> converting an IRB configuration to an RBE one.  Given the IRB
> configuration on a Cisco 7200 like:
>
> bridge irb
> !
> interface BVI10
>  description DSL BVI
>  mac-address 0000.xxxx.yyyy
>  ip address 192.168.10.1 255.255.255.0
>  no ip proxy-arp
>  ip route-cache same-interface
>  no ip mroute-cache
> !
> interface ATM1/0.1 multipoint
>  description DSL #1
>  no ip proxy-arp
>  pvc dsl1 1/301
>  !
>  bridge-group 10
>  bridge-group 10 spanning-disabled
> !
> interface ATM1/0.2 multipoint
>  description BA DSL #2
>  no ip proxy-arp
>  pvc dsl2 1/302
>  !
>  bridge-group 10
>  bridge-group 10 spanning-disabled
> !
> ! repeat for other PVCs
>
>
> I had tinkered a little and tried this:
>
> interface atm1/0
>  mac-address 0000.xxxx.yyyy
> !
> interface atm1/0.301 point-to-point
>  description Verizon DSL RBE
>  range vz-dsl pvc 1/301 1/303
>   exit
>  atm route-bridge ip
>  ip address 192.168.10.1 255.255.255.0
>  ip helper-address some address
>  no ip proxy-arp
>  ip route-cache same-interface
>  no ip mroute-cache
>
> which is pretty much straight out of various Cisco examples.
> Right off the bat I got complaints about duplicate IP addresses.
> It seems that the "range" statement creates clones of the PVC
> configurations, IP address and everything, causing conflicts.
> The first PVC did appear to work, but of course the two clones
> did not.
>
> I had wanted to avoid putting the IP assignment on a loopback
> interface for various reasons.  On some other list I saw a example
> where somebody kept their old BVI interface from the IRB
> configuration, and configured the RBE interfaces as unnumbered with
> reference to the BVI interface.  That seemed a little perverse, but I
> tried it:
>
> interface BVI 10
>  ip address 192.168.10.1 255.255.255.0
> !
> interface atm1/0.301 point-to-point
>  description Verizon DSL RBE
>  range vz-dsl pvc 1/301 1/303
>   exit
>  atm route-bridge ip
>  ip unnumbered BVI10
>
> However none of the PVCs worked (that is, none of the customers could
> be reached, and no ARP entries were created for them.)  Another
> thought is to specifically configure each PVC (not using "range"),
> give the first one an IP address configuration, and configure the
> others as unnumbered with reference to the first PVC.  But that seems
> tacky and unstable.
>
> Any thoughts?  Mostly I am sending this out while I am waiting for the
> next window in the wee hours when I can do a little more trying.
> But if anybody is out there and has comments, I'd be interested in
> hearing..
>
> Yours,
> -mm-
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