Home page logo

nanog logo nanog mailing list archives

Re: maximum active vlans in a cisco 6509
From: "Bob Biver" <bbiver () hotmail com>
Date: Tue, 20 Jun 2000 21:08:17 PDT

okay, now let's change venue:
the hotel has copper pairs to all of the rooms that are terminated on a dslam. this dslam has only ethernet out and on the segment can provision each cable pair/customer to a vlan. these vlans are then aggregated into 10/100 switches in the basement uplinked to the corporate office via gige. then all those customer vlans end up being bridged 1483 to atm pvcs into an ssg.

what box could possible aggregate all this gige, sar to atm, all the while supporting thousands of vlans

many thanks from hotel owners everywhere 8>


If you put all of the users on separate switch ports, then would they be
able to snoop each other's traffic? At least the switches that I have seen
prevent this behavior unless you put a particular switch port in "monitor"

As long as all rooms in this hotel are on separate switch ports, you would
basically be OK even without using VLANs.

Yes, multicast sessions, ARP requests etc can still be snooped.


> 2000-06-20-23:01:45 Roeland Meyer (E-mail):
> > > Bob Biver: Tuesday, June 20, 2000 7:28 PM
> > > the docs say max 250, is this informational or a limit of
> > > spanning tree?
> >
> > If I recall correctly, that's also real close to the maximum
> > number of physical connections to the chasis, with all modules
> > installed. Personally, I've never run anywhere near that number.
> > I don't think it is useful to have less than 2 members in a vlan.
> > You would also be surpassing the bandwidth limitations of that
> > chasis, even if all the connections were 100baseTX.
> For many uses, I think you certainly have a clear and reasonable
> point. But while I don't know what the original poster had in mind,
> I can fantasize a use for thousands of vlans, even on a switch that
> doesn't have thousands of distinct ports. And without necessarily
> exceeding available bandwidth.
> Lessee, suppose I were designing something like an
> internet-access-for-hotel-rooms, or thereabouts. Or suppose
> otherwise I had thousands of users who didn't trust each other, at
> all, who I didn't want to have sniffing each other's traffic, who
> were just wanting to share access to an internet connection, itself
> less than 100BaseT, maybe even much less.
> One way I could fantasize doing it would be to assign a separate
> VLAN to each port of as many different switches, interconnected with
> 802.1Q or ISL, as it took to provide ports to every room. Run one
> 802.1Q line into the one router in this picture, say a Linux box
> using iproute2 for traffic shaping.
> Ok, so maybe 6509s would be way overkill for this application, no
> way you need that kind of backplane bandwidth. But as circumstances
> emerge where you want to have a fully-routed network (next step up
> the protocol ladder from a fully-switched network --- each host gets
> its own dedicated router port) I can anticipate settings where VLANs
> might get abused in a most remarkable way.
> - -Bennett
> Version: GnuPG v1.0.0 (GNU/Linux)
> Comment: For info see http://www.gnupg.org
> iD8DBQE5UDpTL6KAps40sTYRAkSXAJ9zRIAdsIp1xjdS2Vl56WjTeNdmdgCghySl
> Z+zy1YE6u1OW3RopArzAkDg=
> =gFAm

Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com

  By Date           By Thread  

Current thread:
[ Nmap | Sec Tools | Mailing Lists | Site News | About/Contact | Advertising | Privacy ]