Thanks for all the responses. Dug the switches out today and tested. We were all on the right tracks I think. I also put this to the Cisco open forum, and a Cisco CCIE answered my original question saying it was definitely not possible to run etherchannel between two switches with 2 Gigastack modules each. Coming to Cisco's rescue, I received an e-mail from Tom Petzold of Cisco, which doesn't seem to have reached the Newsgroup yet, but his answers were spot on and confirmed by the testing I did today. His e-mail is attached after my mumblings below. If anybody can think of any other tests to try, they're still set up so give me a shout before Monday evening when they get installed elsewhere.
Using all 3524 switches (called A,B and C) Test 1: Connect A to B with one cable - Link Auto's to full duplex Now add a connection from B to C with one cable (on the same Gigastack module) Result - All links revert to half duplex Test 2: Connect A to B with one cable - Link Auto's to full duplex Now add a second Gigastack module to B and connect this to C. Result - All links stay at full duplex. Test 3: Connect A to B with 2 cables (one Gigastack module used in each switch) Result - spanning tree blocks one of the connections (don't know a way of configuring etherchannel for these - they are not subinterfaces of any kind) Test 4: Connect A to B with one cable - Link Auto's to full duplex Put a second Gigastack module in both A and B Connect these with one cable Configure both switches for etherchannel Result - Etherchannel works fine - all ports forwarding Regards, Gaz (Tom Petzold's e-mail follows) Let me see if I can walk through the options. If you hook two switches up with one cable (using only one port on each gigastack GBIC) you will have a 1Gb (2Gb full Duplex) connection. If you have three switches cascaded and use both ports on any gigastack GBIC you will have 1Gb half duplex shared across all the switches. In the previous configuration you can hook the bottom switch back up to the top switch. Since you have a loop now (a to b, b to c, c to a) one port will go into blocking to prevent the loop. Now your question is can I use two gigastack GBICs in both switches and setup an etherchannel. The answer is yes. Connect GBIC 1 in switch A to GBIC 1 in switch 2 and GBIC 2 in switch A to GBIC 2 in switch 2 using 1 cable for each GBIC pair. Then just setup the gigabit ports as an etherchannel group. This will give you the 2Gb (4Gb full duplex) you wanted. What you don't want to do is connect both ports on GBIC 1 to both ports on GBIC 2. I'm not sure what would happen but I think they would go into half duplex and not allow you to setup the etherchannel. Tom Petzold Cisco Systems ""Kelly Cobean"" wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > Guys, If it helps any, here is a quote from Cisco's web site....Link below. > > "Cascaded Stack Connections: > You can connect from three to nine switches in a cascaded stack > configuration. The cascaded stack operates in half-duplex mode." (This > raises the debate about how many switches in the stack again, because now > I've seen conflicting documentation that indicates 9 and 16) > > The link is > http://www.cisco.com/univercd/cc/td/doc/product/lan/c2900xl/gbic/ig_gbic/mam > oins.htm#xtocid357911 > Watch for URL wrap. > > Our Switchstacks contain 9 3548's here, and the uplink ports with fiber GBIC > modules default to full duplex, while the gigastack module ports default to > half duplex. I think one of reasons for this is the fact that you are > effectively splitting the port in half by connecting each of the two > gigastack ports to different switches. Hope this helps. > > Kelly Cobean, CCNP, CCSA, ACSA, MCSE, MCP+I > Network Engineer > GRC International, Inc., an AT&T company > > > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of > Gaz > Sent: Thursday, March 21, 2002 2:01 PM > To: [EMAIL PROTECTED] > Subject: Re: Gigastack Etherchannel [7:39033] > > > Ole, > > Good question.......... Dunno! > > I was just going to suggest that one 3548 could only talk to one other > switch at full duplex. The Gigastack bus may equate to a shared media once > another switch is attached, so needs to go to half duplex. > This must be different for something like a 3508, as a 3508 can definitely > take multiple full duplex connections when used as the hub of a star > configuration. > > In fact now I've finished writing it, it seems reasonable. I will test this > tomorrow as well. > > Anybody pick holes in that theory? > > > Gaz > > > > ""Ole Drews Jensen"" wrote in message > [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > If you have three 3548's - A, B and C, and you have 1 GigaStack module in > A > > where only one connector is connected to one connector on a GigaStack > module > > in B, and 1 GigaStack module in C where only one connected is connected to > > one connector on a second GigaStack module in B. Would that make a Full > > Duplex on the connections since only one port is used on each GigaStack > > module, or would it end up in Half Duplex anyway, since you have a total > of > > three switches? > > > > Ole > > > > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > Ole Drews Jensen > > Systems Network Manager > > CCNP, MCSE, MCP+I > > RWR Enterprises, Inc. > > [EMAIL PROTECTED] > > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > http://www.RouterChief.com > > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > Need a Job? > > http://www.OleDrews.com/job > > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > > > > > > > > > -----Original Message----- > > From: Georgescu, Aurelian [mailto:[EMAIL PROTECTED]] > > Sent: Thursday, March 21, 2002 11:56 AM > > To: [EMAIL PROTECTED] > > Subject: RE: Gigastack Etherchannel [7:39033] > > > > > > They can be used in full-duplex mode on point-to-point links (aka using > only > > one connector on each GigaStack, one at each end of the cable). If you > > daisy-chain them they default to half-duplex. > > > > Aurelian > > > > -----Original Message----- > > From: Ole Drews Jensen [mailto:[EMAIL PROTECTED]] > > Sent: Thursday, March 21, 2002 12:02 PM > > To: [EMAIL PROTECTED] > > Subject: RE: Gigastack Etherchannel [7:39033] > > > > GigaStack GBIC's are Full Duplex: > > > > ELVIS#show int gigabitEthernet 0/1 > > GigabitEthernet0/1 is up, line protocol is up > > Hardware is Gigabit Ethernet, address is 0002.fd13.52f1 (bia > > 0002.fd13.52f1) > > MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec, > > reliability 255/255, txload 1/255, rxload 1/255 > > Encapsulation ARPA, loopback not set > > Keepalive not set > > Auto-duplex (Full), link type is autonegotiation, media type is > > CX_GIGASTACK > > output flow-control is off, input flow-control is off > > ARP type: ARPA, ARP Timeout 04:00:00 > > GigaStack module(0.2) in GBIC slot. link1 is up, link2 is down > > Last input 00:00:06, output 00:00:01, output hang never > > Last clearing of "show interface" counters 11w1d > > Queueing strategy: fifo > > Output queue 0/40, 0 drops; input queue 0/75, 0 drops > > 5 minute input rate 107000 bits/sec, 15 packets/sec > > 5 minute output rate 91000 bits/sec, 16 packets/sec > > 122086095 packets input, 1719966070 bytes, 0 no buffer > > Received 3149732 broadcasts, 0 runts, 0 giants, 0 throttles > > 0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored > > 0 watchdog, 163799 multicast, 0 pause input > > 165588418 packets output, 149633091 bytes, 0 underruns > > 0 output errors, 0 collisions, 0 interface resets > > 0 babbles, 0 late collision, 0 deferred > > 0 lost carrier, 0 no carrier, 0 pause output > > 0 output buffer failures, 0 output buffers swapped out > > > > Hth, > > > > Ole > > > > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > Ole Drews Jensen > > Systems Network Manager > > CCNP, MCSE, MCP+I > > RWR Enterprises, Inc. > > [EMAIL PROTECTED] > > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > http://www.RouterChief.com > > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > Need a Job? > > http://www.OleDrews.com/job > > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > > > > > > > > > -----Original Message----- > > From: Jeffrey Reed [mailto:[EMAIL PROTECTED]] > > Sent: Thursday, March 21, 2002 10:22 AM > > To: [EMAIL PROTECTED] > > Subject: RE: Gigastack Etherchannel [7:39033] > > > > > > I'm not sure, but I thought I read somewhere that the GigaStack GBICs are > > half duplex. I think I read somewhere that you shouldn't use them in an > > environment that requires QOS. If this is true, your throughput would be > > better with 1000B-T GBICs or Fiber GBICs running at full duplex. > > > > Jeffrey Reed > > Classic Networking, Inc. > > > > -----Original Message----- > > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of Gaz > > Sent: Thursday, March 21, 2002 10:16 AM > > To: [EMAIL PROTECTED] > > Subject: Gigastack Etherchannel [7:39033] > > > > Hi all, > > > > Been searching all over CCO for this info....anybody know for sure? > > > > > > Using Gigastack, can both slots be used as "Gigastack Etherchannel" (ie > all > > four ports (two on each module)) to provide 4Gb link. > > > > Scenario would be a 3508 with two Gigastack modules and 3548 with two > > Gigastack modules - connected with four gigastack cables. > > Various web pages show 2Gb full duplex using Gigastack and also mention > 4Gb > > Full Duplex using Gigabit Ethernet. Even though the latter was on a > > Gigastack data sheet, it was worded as though (or could mean) an > alternative > > was to use Gigabit Ethernet at 4Gb. > > > > Hopefully I've got the question over - Basically, I know 4Gb is possible > > with fibre SX/LX etc, but what about Gigastack? > > > > Thanks, > > > > Gaz Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=39153&t=39033 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
