| T.R | Title | User | Personal
Name | Date | Lines |
|---|
| 2082.1 | partly answered off line | STROP::LAYLAND | Iligitami nil Carborundum | Wed Mar 15 1995 14:38 | 16 |
| The question was answered off-line, but there still remains the question concerning
multiple bridges in the same 90 back-plane. Also what of other rules in the docs.
>John, my understanding is that the DECbridge 90 was forced to implement
>full spanning tree because some of our older bridges could not handle
>"leaf bridges" in the tree. If you exceed the 200 node limit on the
>workgroup port, whether by adding another bridge or not, the DECbridge
>90 will go into Flood mode. Note that Flood mode is board rev dependent;
>original DECbridge 90's did not do Flood mode. I think all DECbridge
>90FL's did flood mode.
Regards John
|
| 2082.2 | | NPSS::JOHNSON | Mike J., Network Products Support | Wed Mar 15 1995 21:42 | 21 |
| John,
Since I was party to the full text of the off line messages between you and
Jack, I'll throw in my two cents worth here as well.
There are a couple reasons for not putting multiple DB90's in the same hub.
The first is that there is a very real possibility that someone will form a
loop, external to the hub, and a subsequent failure, also external to the hub,
will cause ALL of your backbone traffic to transferse the DB90 pair.
Considering the DB90's performance capabilities, that would be bad news.
Second, when a DB90 "floods" it does NOT act like a "backbone bridge". It
actually acts more like a store and forward REPEATER with some degree of
protocol filtering capability.
If you remember and consider the ramifications of just this one thing, the
limitations become much easier to understand. The DB90 maintains only ONE
forwarding table, and that table ONLY references the WORKGROUP (hub backplane)
side.
/mj
|
| 2082.3 | | STROP::LAYLAND | Iligitami nil Carborundum | Mon Mar 20 1995 10:23 | 0 |
| 2082.4 | The Brouter is being installed ! | STROP::LAYLAND | Iligitami nil Carborundum | Mon Mar 20 1995 10:51 | 18 |
| Thanks for the reply Mike..
I understand your comments. There are however a couple of points that need
clarification.
Some people are putting Brouter 90's in the same backplane as the bridge 90, and
claiming that it is a legal configuration since v3.9, (flood mode), was introduced.
The other point is if the above is legal, the support centre would claim it as
illegal since the documentation does not allow it.
From what you are saying the problems are more likely to be bad configurations than
a problem of interaction with other bridges. If that is so then we have the
classic situation of knowing it works but is unsupported. The answer to my
specific situation would be to replace the 90 bridge with a repeater the Brouters
could now be put into the backplane. But there will be problem of other sites
where Brouters and bridge90's are mixed in the same backplane, when/if a fault
occurs and it is deemed unsupported.
John
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