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VLANs, trunking and dot1q questions

I've been wrangling with connecting a Catalyst 4006 (running CatOS) to a Cisco GbESM switch module (running IOS) in an IBM BladeCenter.

One area in which I'm still not sure how everything "fits together" is in terms of VLANs (native and not), trunking and 802.1q. The problems stem from the way the GbESM modules in the BladeCenters are setup, but I'm temporarily unable to change how they work. Specifically, the GbESM ships with it's management ports in VLAN 1 and all other ports in VLAN 2. Unfortunately for me, all the ports on my Catalyst 4006 are in VLAN 1.

If I don't set dot1q to "off", I get this when (in CatOS) when I try and connect the GbESM to the Catalyst:

CAT4000-1> (enable) sh port 4/20

  • = Configured MAC Address

Port Name Status Vlan Level Duplex Speed Type

----- ------------------ ---------- ---------- ------ ------ -----

------------ 4/20 connected trunk normal a-full a-1Gb

10/100/1000

Note that the VLAN status is "trunk". In this example, if the VLAN status is "trunk", I am unable to pass any data to the BladeCenter -- I presume that it's expecting traffic on VLAN 2, and it's only receiving traffic on VLAN 1 (which is what the 4006 has all of its ports in) so it's not receiving any data. However, if I turn off dot1q (using this command: set trunk 4/20 off dot1q 1-1005,1025-4094), on the port connecting the two switches, I get this:

CAT4000-1> (enable) sh port 4/20

  • = Configured MAC Address

Port Name Status Vlan Level Duplex Speed Type

----- ------------------ ---------- ---------- ------ ------ -----

------------ 4/20 connected 1 normal a-full a-1Gb

10/100/1000

And now everything works fine. My question is, what exactly is the "set trunk 4/20 off dot1q 1-1005,1025-4094" command accomplishing?

From CatOS, I can see this warning: "2007 Jan 30 07:00:33 EST -05:00

%CDP-4-NVLANMISMATCH:Native vlan mismatch detected on port 4/20". Am I to presume that the dot1q command effectively tells the 4006 to ignore the VLANs that it's seeing, and just pretend everything is in VLAN 1? I suppose my ultimate question is, why does it work this way but no others?

I have a reasonable idea of how VLANs work, but when it comes to trunking and 802.1q I fear that I am getting a little lost. Any replies helping to clarify this would be, by me, appreciated!

TIA and HAND,

Chris

Reply to
Chris
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Hello Chris , I'm jun from Japan I set up a GbESM switch modulein an IBM BladeCenter H today. I study them a little and hava an idea.

Probably, Catalyst 4006 send VLAN info to BladeCenter as Vlan 1, GbESM external port drop all data belonging to Vlan1, because vlan 1 is used for management module. By setting dot1q to "off", 4006 will not send VLAN info with data. If GbESM recieved that data which don't have Vlan info, GbESM add Vlan info to Vlan2. (external port was set to access vlan 2) so connection can be established.

Probably

Reply to
Jun

Arigato gozaimasu Jun! How have you connected your GbESM, do you have the ports in VLAN 1 or VLAN 2? I would like all ports to be in the same VLAN, but I do not know if it is possible. :-(

Chris

messagenews: snipped-for-privacy@h3g2000cwc.googlegroups.com...

Reply to
Chris

Hi Chris,

I'm not sure this is your question. my English problem I setup GbESM via the management module (192.168.70.125 default ) Management module's web interface have a web interface and telnet session to GbESM It is not able to access GbESM via External port by default . Workaround is create another VLAN ( ex VLAN 10) Give the ip address to the VLAN 10,so we can access to GbESM via external port.

messagenews: snipped-for-privacy@h3g2000cwc.googlegroups.com...

Reply to
Jun

Hi Chris, Long thread, and I'm not sure exactly where you are at on this. Did you get your questions answered? There is an IBM red paper that might be of help with your questions at:

formatting link
5.3 talks about how to select a management path for the IGESM (recommend over the MM uplinks, NOT over the IGESM uplinks). Section 7 discusses data connectivity for the IGESM uplinks, but does not include connecting the IGESM to a CatOS device upstream (this can be done, but you do have to understand the ways to do it, which would require more information). Let me know if you?re still stuck and I will try to assist. Thanks, Matt

Reply to
Matt Slavin

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