Sign in with
Sign up | Sign in
Your question

Help needed about Implementation of "Spanning Tree Protoco..

Last response: in Networking
Share
Anonymous
September 16, 2005 10:54:13 PM

Archived from groups: comp.dcom.sys.cisco,comp.dcom.lans.ethernet (More info?)

A switch contains 3 uplinks which are on WAN side and there 30 LAN
ports for subscriber side, how to implement Spanning tree protocol
(802.1d) in this switch?. Can somebody suggest how to implement STP and
what are the things has to take care on interface level?. Thanks in
advance. We have chip called "xyz" which inter connects WAN and LAN.
Thanks in advance.
Anonymous
September 17, 2005 8:30:09 PM

Archived from groups: comp.dcom.sys.cisco,comp.dcom.lans.ethernet (More info?)

In article <1126922053.749767.128790@o13g2000cwo.googlegroups.com>,
GS <globalswamy@hotmail.com> wrote:
:A switch contains 3 uplinks which are on WAN side and there 30 LAN
:p orts for subscriber side, how to implement Spanning tree protocol
:( 802.1d) in this switch?. Can somebody suggest how to implement STP and
:what are the things has to take care on interface level?. Thanks in
:advance. We have chip called "xyz" which inter connects WAN and LAN.

Sorry, GS, your question looks suspiciously like a course assignment.

If you are actually working for a company that designs switches,
then I would expect you to have read the appropriate RFCs throroughly
and to ask -specific- questions -- and I would expect that the
company would have hired someone who had switch design experience.

--
'The short version of what Walter said is "You have asked a question
which has no useful answer, please reconsider the nature of the
problem you wish to solve".' -- Tony Mantler
Anonymous
September 18, 2005 12:38:30 PM

Archived from groups: comp.dcom.sys.cisco,comp.dcom.lans.ethernet (More info?)

Actually I am looking for some info about how spanning tree protocol
can be interfaced with WAN and LAN ports?, that's all I needed.
Related resources
Can't find your answer ? Ask !
Anonymous
September 18, 2005 8:17:12 PM

Archived from groups: comp.dcom.sys.cisco,comp.dcom.lans.ethernet (More info?)

In article <1127057910.822991.101990@g14g2000cwa.googlegroups.com>,
GS <globalswamy@hotmail.com> wrote:
:Actually I am looking for some info about how spanning tree protocol
:can be interfaced with WAN and LAN ports?, that's all I needed.

The Spanning Tree Protocol doesn't care whether a port is a WAN
or LAN port. You can send BPDU on a WAN link.

Whether it is worth sending BPDUs or not depends upon whether there is
any possibility that the far hop of the WAN link might have topology
loops that you need to arbitrate between.


Perhaps you are asking about a different matter, which is to say
tunneling of BPDUs over WAN links, so that you can have an
extended "layer 2" path resolution instead of using a "routing"
path resolution? If that's what you are trying to do, then this
article might be of interest:

http://www.netcraftsmen.net/welcher/papers/metroeth01.h...
--
Feep if you love VT-52's.
Anonymous
September 20, 2005 8:41:00 AM

Archived from groups: comp.dcom.sys.cisco,comp.dcom.lans.ethernet (More info?)

This whole STP/Bridge implementtaion does really care about hardware
interfaces (physical ports)? Or is it everything is in software only,
for example, if the port's state is changed (if the port is got
disconnected)?. Thanks.
Anonymous
September 20, 2005 7:02:31 PM

Archived from groups: comp.dcom.sys.cisco,comp.dcom.lans.ethernet (More info?)

In article <1127216460.615943.293030@f14g2000cwb.googlegroups.com>,
GS <globalswamy@hotmail.com> wrote:
:This whole STP/Bridge implementtaion does really care about hardware
:interfaces (physical ports)? Or is it everything is in software only,
:for example, if the port's state is changed (if the port is got
:D isconnected)?. Thanks.

I'm still not sure what you are trying to do.

STP is a layer 2 protocol, not a routed protocol. If you have a WAN
port which is transmitting BPDU's to you, then the STP information
so carried will be taken into account in the construction of the tree.

If you had a situation where you had multiple WAN connections that were
linked together at layer 2 on the remote end and so were determined by
STP to be part of the same tree, then because WAN links are often much
slower than LAN links, those WAN links would tend to be deemed to have
a high cost, you could end up with all the WAN traffic directed to
the WAN link that happened to have the lowest MAC address (or based
on one of the other STP resolution criteria.)

It would, however, be quite unusual for multiple WAN links to be
joined together remotely in a common tree -- rare enough that
*probably* it would only occur if you were deliberately bridging BPDU
from a remote site to implement an extended LAN.

If the WAN links sent you BPDU at all (which is not particularily
likely) then they would very likely appear to be distinct leafs, to
be detected by STP as not having any topology loops. There might be
a layer 3 topology loop involved, but STP is not designed to detect
layer 3 topology loops.

If the STP has determined that a particular WAN link is a leaf,
then when that WAN connection goes down, if you are using classic
STP then the spanning tree will be recalculated -- and will be
determined to be exactly the same as it was before. If you are
are using RSTP (Rapid Spanning Tree Protocol) then in the same
circumstances, the switches would have figured out that that WAN
link was not a potential backup link, and so would know that the
topology would not change, and would supress notification of the
event to the other switches.
--
Goedel's Mail Filter Incompleteness Theorem:
In any sufficiently expressive language, with any fixed set of
email filtering algorithms, there exists at least one spam message
which the algorithms are unable to filter out.
!