>Many hubs (including most old Bay/Synoptics hubs) can have an ip address
>assigned to the hub itself (not to individual ports on the hub) for management
>purposes. In this case the switch could indeed have an arp cache
>entry for the
>hub.
>
>JMcL
>---------------------- Forwarded by Jenny Mcleod/NSO/CSDA on 14/07/2000 15:31
>---------------------------
Good points. When people first start looking at products, they must
realize that terminology varies from vendor to vendor, and even
within a vendors, the product designs represent responses to
perceived market needs, not necessarily specific OSI layering.
Cabletron, for example, tends to call everything a hub, even though
it may have full layer 3 routing. Their usage of hub is what I'd
call a card cage. Other companies call everything a switch, because
they have a market message "routing bad/switching good."
Terminology
-----------
Let's start with layer 1 repeaters--basic hubs. Basic hubs share
bandwidth domains, collision domains (in CSMA/CD media), broadcast
domains, and management domains.
Cascaded hubs have the same shared domains, but are cabled together
to give more ports into the same domain.
Stacked hubs add management. They have a single IP address that
provides hub management services for one hub or for a cascade of hubs.
"Hubs" that offer speed conversion typically have an internal bridge
card, but don't participate in the spanning tree.
Full-featured bridges participate in the spanning tree. They may be
SNMP manageable, and, if so, have an IP address.
LAN switches participate in the spanning tree, and also use
microsegmentation -- one device per port. They may participate in
VLANs. T hey may be SNMP manageable, and, if so, have an IP address.
Layer 3 switch is a marketing, not a technical term. It's really a
router that implements its forwarding table in hardware.
And the Band Played On...
-------------------------
Management can be in-band or out-of-band. In-band management is in
the same broadcast domain as at least some of the user traffic.
Out-of-band management is in a separate management subnet.
I prefer out-of-band management, because if management isn't
accessible due to a user broadcast storm, where does that leave you
operationally?
>
>Omar Khawaja <[EMAIL PROTECTED]> on 13/07/2000 11:12:56
>
>Please respond to Omar Khawaja <[EMAIL PROTECTED]>
>
>
>To: [EMAIL PROTECTED]
>cc: (bcc: JENNY MCLEOD/NSO/CSDA)
>Subject: Re: connectivity problem
>
>
>
>hubs usually don't have NICs for their ports. they are functionally
>layer 1 devices, so therefore don't understand what a MAC address is.
>Bridges and Switches, on the contrary, are layer 2 devices and do
>unnderstand MAC addresses..
>
>Dick Silva wrote:
> >
> > / Question here:
> > You say if you have six hosts (workstations) and the hub you have 7 MAC
> > addresses.
> > Now I understand the six workstations have NICs. But does the
>hub port also
> > have a NIC?
> > Would a printer connected to the same hub port have a NIC also? I
> > understand that the hub port and printer would each be considered a host.
> > So does this mean that all hosts also have NICs?
> > Dick Silva
> >
> > -----Original Message-----
> > From: Chris H <[EMAIL PROTECTED]>
> > To: [EMAIL PROTECTED] <[EMAIL PROTECTED]>;
>[EMAIL PROTECTED]
> > <[EMAIL PROTECTED]>; [EMAIL PROTECTED] <[EMAIL PROTECTED]>
> > Date: Tuesday, July 11, 2000 10:53 PM
> > Subject: RE: connectivity problem
> >
> > >
> > >The ARP cache should contain all MAC addresses for the port you have the
> > hub
> > >connected to. So for the sake of arguement, you have 6 workstations
> > >connected to that hub, the switch should cache 7 MAC addresses, the 6
> > >workstations and the hub.
> > >
> > >show ip arp fastethernet [port number]
> > >
> > >Make sure you also have spanning tree enabled on that port. If it doesn't
> > >work, like someone else said, check layer 1, replace the hub, etc. etc.
> > >etc....
> > >
> > >I also know that the old Bay hubs have some type of Management Menu driven
> > >code loaded as well. I'm not sure if you have to specify an
>uplink port or
> > >what, but you may want to check the hub itself.
> > >
> > >
> > >Chris
> > >
> > >>From: Daniel Cotts <[EMAIL PROTECTED]>
> > >>Reply-To: Daniel Cotts <[EMAIL PROTECTED]>
> > >>To: "'Don Dettmore'" <[EMAIL PROTECTED]>, [EMAIL PROTECTED]
> > >>Subject: RE: connectivity problem
> > >>Date: Tue, 11 Jul 2000 09:52:18 -0500
> > >>
> > >>Maybe a layer one problem?
> > >>Seems that the switch can see the hub. The hub can't see the switch. Do
> > you
> > >>have link both ends? Have you substituted the patch cable between them?
> > >>Alternatively do you have a packet analyzer such as EtherPeek to stick in
> > >>the hub to see if it sees the pings, arp requests from the switch side?
> > >>
> > >> > -----Original Message-----
> > >> > From: Don Dettmore [mailto:[EMAIL PROTECTED]]
> > >> > Sent: Tuesday, July 11, 2000 8:04 AM
> > >> > To: [EMAIL PROTECTED]
> > >> > Subject: connectivity problem
> > >> >
> > >> >
> > >> > Here is an interesting problem.
> > >> >
> > >> > I have a client with a Cisco 2924XL switch. Most stations are
> > >> > directly connected to the switch, however off of one of the switch
> > >> > ports is an old Bay 10mb/s hub.
> > >> >
> > >> > The problem is that stations connected to the hub cannot communicate
> > >> > with stations connected to the switch. Switch stations CAN
> > >> > communicate with switch stations, and hub stations CAN communicate
> > >> > with hub stations.
> > >> >
> > >> > The switch port connected to the hub appears to recognize the hub -
> > >> > it is up/up and has detected 10mb half duplex. I tried manually
> > >> > entering these settings with no effect.
> > >> >
> > >> > It appears to be an arp problem - if I debug arp and then try to ping
> > >> > a station connected to the hub, arps are sent out, but no replys are
> > >> > received. This happens whether the switch itself tries to ping a hub
> > >> > host, or a if a switch station does so. Interestingly enough tho, if
> > >> > a hub station pings another hub station, the arp shows up on the
> > >> > switch debug console - it is definitely seeing the traffic!
> > >> >
> > >> > Any suggestions would be greatly appreciated.
> > >> >
> > >> > Thanks!
> > >> >
> > >> > Don Dettmore
> > >> > CCNP, MCSE, CNE
> > >> >
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