Mailing List Archive

Hi,

as a preface, I know the standard answer is "do not do that", but due to
local constraints, I can't avoid it...

If I have a bridge-group on an ASR9001 with (rapid per-vlan) spanning-tree
active, everything works "as expected".

Except for TCN-induced mac-flushes, that is

- somewhere else in this STP topology, a link fails
- adjacent switches notice and send STP TCNs
- the ASR9001 would now need to send out packets for a given host
to a different interface (I've constructed the outage purposely that
way to see if it works) - normally, STP TCNs force a MAC table flush

- this does not happen - it sticks to its MAC tables unless a packet
*from* that host is seen, and then it updates everything fine.

Reading documentation on STP modes on the ASR9001 is a bit sparse - and
all mentioning of TCN lead to "MST", which is a no-go. In general, and
even more in this particular environment...

So - since all the knobs are well-hidden - is there a knob I have not
yet found to make the ASR9001 flush MAC tables on STP TCN, or is this
just "not supported"?


IOS XR version 6.5.3SP1 (32 bit, as ASR9001).

This is the config:

interface TenGigE0/0/0/0.3028 l2transport
encapsulation dot1q 3028
rewrite ingress tag pop 1 symmetric
mtu 1518

interface TenGigE0/0/1/0.3028 l2transport
encapsulation dot1q 3028
rewrite ingress tag pop 1 symmetric
mtu 1518

l2vpn
bridge group vlandb
bridge-domain v3028
interface TenGigE0/0/0/0.3028
!
interface TenGigE0/0/1/0.3028
!
routed interface BVI3028
!
!
!
panning-tree pvrst vlandb
vlan 3028
priority 8192
!
interface TenGigE0/0/0/0
!
interface TenGigE0/0/1/0
!


--
"If was one thing all people took for granted, was conviction that if you
feed honest figures into a computer, honest figures come out. Never doubted
it myself till I met a computer with a sense of humor."
Robert A. Heinlein, The Moon is a Harsh Mistress

Gert Doering - Munich, Germany gert@greenie.muc.de