Transit LAN vs. Individual LANs

On Feb 24, 2006, at 9:03 PM, Scott Weeks wrote:

> I have 2 core routers (CR) and 3 access routers (AR)
> currently connected point-to-point where each AR
connects to
> each CR for a total of 6 ckts.  Now someone has decided
to
> connect them with Gig-E.  I was wondering about the
benefits
> or disadvantages of keeping the ckts each in their own
> individual LANs or tying them all into one VLAN for a
> "Transit LAN" as those folks that decided
on going to Gig-E
> aren't doing any logical network architecting (is that
a
> real word?).

Personally, I like the to KISS, so one big 'transit LAN'.

An argument could be made for individual VLANs to keep
things like b- 
cast storms isolated.  But I think the additional complexity
will  
cause more problems than it will solve.

Or maybe I'm just too dumb to keep up with the additional
complexity. 

-- 
TTFN,
patrick

 > An argument could be made for individual VLANs to keep
things 
> like b- cast storms isolated.  But I think the
additional 
> complexity will cause more problems than it will solve.

Vlans will not stop all typres of broadcast storm.

--On February 25, 2006 11:04:12 AM -0500 "Patrick W.
Gilmore"
<patrickianai.net> wrote:

> 
> On Feb 24, 2006, at 9:03 PM, Scott Weeks wrote:
> 
>> I have 2 core routers (CR) and 3 access routers
(AR)
>> currently connected point-to-point where each AR
connects to
>> each CR for a total of 6 ckts.  Now someone has
decided to
>> connect them with Gig-E.  I was wondering about the
benefits
>> or disadvantages of keeping the ckts each in their
own
>> individual LANs or tying them all into one VLAN for
a
>> "Transit LAN" as those folks that
decided on going to Gig-E
>> aren't doing any logical network architecting (is
that a
>> real word?).

In my experience either solution has tradeoffs and the
correct
one depends greatly on your traffic patterns.  Having said
that,
what I find causes most of the problems in either solution
is
when the Layer 3 topology starts to diverge from the Layer 2
topology.

Owen

-- 
If it wasn't crypto-signed, it probably didn't come from
me.

On Sat, 25 Feb 2006, Neil J. McRae wrote:

>
>  > An argument could be made for individual VLANs to
keep things
> > like b- cast storms isolated.  But I think the
additional
> > complexity will cause more problems than it will
solve.
>
> Vlans will not stop all typres of broadcast storm.
>

So, perhaps I missed the earlier explanation, but why use
switched
segments at all? if the purpose is to connect routers to
routers putting
something that WILL FAIL in the middle is only going to
increase your
labor costs later :(

So, for router-router links, GE doesn't have to mean
switched...

--On February 25, 2006 8:09:22 PM +0000 "Christopher
L. Morrow"
<christopher.morrowverizonbusiness.com> wrote:

> 
> 
> On Sat, 25 Feb 2006, Neil J. McRae wrote:
> 
>> 
>>  > An argument could be made for individual
VLANs to keep things
>> > like b- cast storms isolated.  But I think the
additional
>> > complexity will cause more problems than it
will solve.
>> 
>> Vlans will not stop all typres of broadcast storm.
>> 
> 
> So, perhaps I missed the earlier explanation, but why
use switched
> segments at all? if the purpose is to connect routers
to routers putting
> something that WILL FAIL in the middle is only going to
increase your
> labor costs later :(
> 
> So, for router-router links, GE doesn't have to mean
switched...

Very true.  In fact, GE is even easier because part of the
GE standard
for UTP requires it to be Auto-MDI-Sensing (MDI vs MDI-X is
handled
automatically in ALL compliant GE/TP interfaces).  Thus, you
can use
any eia-568[ab] cable, straight or crossed between them. 
(Note, USOC
cables still won't work, it has to be 568a or 568b pairing)


Owen



-- 
If it wasn't crypto-signed, it probably didn't come from
me.

On Feb 25, 2006, at 9:23 PM, Owen DeLong wrote:

>
>
> --On February 25, 2006 8:09:22 PM +0000
"Christopher L. Morrow"
> <christopher.morrowverizonbusiness.com>
wrote:
>
>>
>>
>> On Sat, 25 Feb 2006, Neil J. McRae wrote:
>>
>>>
>>>> An argument could be made for individual
VLANs to keep things
>>>> like b- cast storms isolated.  But I think
the additional
>>>> complexity will cause more problems than it
will solve.
>>>
>>> Vlans will not stop all typres of broadcast
storm.
>>>
>>
>> So, perhaps I missed the earlier explanation, but
why use switched
>> segments at all? if the purpose is to connect
routers to routers  
>> putting
>> something that WILL FAIL in the middle is only
going to increase your
>> labor costs later :(
>>
>> So, for router-router links, GE doesn't have to
mean switched...
>
> Very true.  In fact, GE is even easier because part of
the GE standard
> for UTP requires it to be Auto-MDI-Sensing (MDI vs
MDI-X is handled
> automatically in ALL compliant GE/TP interfaces).

Unfortunately it seems that not all devices actually
implement MDI/MDI-X

IEE Std 802.3ab-1999, 40.4.4 (Page 93) says:
"Implementation of an automatic MDI/MDI-X
configuration is optional  
for 1000BASE-T devices".

IEE Std 802.3ab-1999, 40.8,2 (Page 93) says:
"Although the automatic MDI-<DI-X configuration
(see 40.4.4) is not  
required for successful operation of 1000BASE-T, is is a
functional  
requirement that a cross-over function be implemented in 
every link  
segment to support the operation of Auto-Negotiation"

Now, seeing as Auto-Negotiation is required, it implies that
 
automatic MDI/MDI-X is also required -- however, certain
vendors seem  
to ignore this....

W




> Thus, you can use
> any eia-568[ab] cable, straight or crossed between
them.  (Note, USOC
> cables still won't work, it has to be 568a or 568b
pairing)
>
>
> Owen
>
>
>
> -- 
> If it wasn't crypto-signed, it probably didn't come
from me.

On Mon, 27 Feb 2006, Warren krishnai wrote:
> Now, seeing as Auto-Negotiation is required, it implies
that automatic 
> MDI/MDI-X is also required -- however, certain vendors
seem to ignore 
> this....

Which ones?

-Dan