From: ccie2be (ccie2be@nyc.rr.com)
Date: Mon Apr 11 2005 - 11:37:49 GMT-3
Hi guys,
How does STP view a multi-access interface such multipoint frame relay or
multipoint ATM?
For example, suppose you have a F/R hub and spoke where all interfaces are
in the same bridge group. Between spoke 1 and 2, there's a separate physical
link and spoke 1 is elected the root bridge for bridge-group 2.
This means one but only one of the pvc's on the hub router should be put
into a STP blocking state since if both pvc's are blocked, then the hub
router is isolated.
Now, suppose the hub router is elected root and therefore one of the ppp
interfaces between the spokes is put into blocking state. What happens when
frames from spoke 1 need to reach spoke 2. Will the hub router forward
frames from 1 pvc to the other pvc? Why or why not?
Now, suppose the hub router is configured with a separate p2p sub-interfaces
going to each spoke. Will the behavior of the hub be any different than
when configured with one multipoint interface with 2 pvc's? IOW, will the
hub consider each p2p subinterface a separate interface in its bridge table?
Can someone explain what I should understand about this so that I know how
to go about dealing with such a scenario.
TIA, Tim
Hub router:
interface Serial0/0
frame-relay map bridge 103 broadcast
frame-relay map bridge 104 broadcast
no frame-relay inverse-arp
bridge-group 2
Spoke 1
interface Serial0/0
desc To Hub
frame-relay map bridge 401 broadcast
no frame-relay inverse-arp
bridge-group 2
int Serial0/1
desc To Spoke 2
encap ppp
bridge-group 2
Spoke 2
int Serial0/0
desc To Hub
frame-relay map bridge 301 broadcast
no frame-relay inverse-arp
bridge-group 2
int Serial0/1
desc To Spoke 1
encap ppp
bridge-group 2
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