LAGs, VLANS, and Xserve

Question

Hello all-

I have a Powerconnect 2724 connected to, among other things, an Intel Xserve. The Xserve has two NIC's in it and are aggregated together. I'm trying to form a LAG for the two ports in the switch that it is connected to without much luck. I have the users guide which dictates the following:

• Link Aggregation is allowed between two devices only.
• All ports within a LAG must be the same media type.
• A VLAN is not configured on the port.
• The port is not assigned to a different LAG.
• An available MAC address exists which can be assigned to a port.
• Auto-negotiation mode is not configured on the port.
• The port is in full-duplex mode.
• All ports in the LAG have the same ingress filtering and tagged modes.
• All ports in the LAG have the same back pressure and flow control modes.
• All ports in the LAG have the same priority.
• All ports in the LAG have the same transceiver type.
• The device supports up to six LAGs, and up to four ports in each LAG.

I understand it all, but I'm having a problem removing the ports from a VLAN. The default VLAN 1 is setup for every port. I cannot remove the two ports from that VLAN. It just won't let me. When I create a new VLAN (#2) I check every port except the two that cannot be in it and apply the changes. What it looks like now though is that I have two VLANS emcompassing every port on 1, and every port but 2 on 2. When I create the LAG for the two ports it completely strips the Xserve of all network connectivity. To my knowledge I should be able to remove the two ports from VLAN 1 or just have VLAN 2 override the settings for VLAN 1. I'm sorry if this is confusing (it is for me as well) but I'm at a loss here. Thanks for all your help.

Matt

formz1 · Answer

Okay some more information:

I figured out that in order for the two ports to be in the LAG I have to set the PVID to VLAN ID that does not include those ports. I got that, go me. :)

However, even when the LAG is configured it strips the Xserve of connectivity. I get a message from the server saying "The port on the switch that the device is connected to doesn't seem to have 802.3ad Link Aggregation enabled." Unfortunately I just turned it ON and its saying it doesn't find it. When I have LAG turned OFF it seems to think it's working, however I'm still getting duplicate IP errors on the server with LAG is off. Frustration is setting in.

cerbera_a84f2d · Answer

Intel support two types of link agg teams - static link agg and dynamic link agg ( also known as LACP )

The 2700 switch family only supports 802.3ad static link agg - make sure you have configured the NIC team for static.

You might find this useful

http://support.intel.com/support/network/sb/CS-020140.htm

formz1 · Answer

Hi cerbera,

Thanks for the information. Excuse my ignorance on the matter but since the switch only supports static link that means it DOESN'T support LACP? Or is does LACP encompass static and dynamic aggregation? The reason I ask is because my xserve supports link aggregation ONLY using LACP.

Thanks

Matt

cerbera_a84f2d · Answer

I suspect thats the problem.

As far as I know, the PowerConect 2700 is strictly 802.3ad static i.e. NOT LACP

If the server is LACP, then it won't see LACP at the other end, and so won't see it as an aggregate.

formz1 · Answer

Actually I was just looking at Dell's switches and found this:

PowerConnect 2724:

http://www.dell.com/content/products/productdetails.aspx/pwcnt_2724?c=us&cs=04&l=en&s=bsd

Link Aggregation, up to six groups and up to four aggregated links per group (IEEE 802.3ad)

PowerConnect 2748 (the next one up):

http://www.dell.com/content/products/productdetails.aspx/pwcnt_2748?c=us&cs=04&l=en&s=bsd

Industry-standard link aggregation adhering to IEEE 802.3ad standards

Now I'm confused. Is the 2724's link aggregation NOT up to IEEE standards? It looks like they both say the same thing but neither shows explicit LACP support. What switch does?

Thanks

Matt

formz1 · Answer

Thanks so much for the help. Now I have to figure out the pros and cons of either buying a switch that does support LACP, or removing link aggregation from our server. This is going to be fun. :)

Thanks for all your help

Matt

cerbera_a84f2d · Answer

Although its part of the standard, LACP support isn't mandated by 802.3ad; so a switch that supports 802.3ad doesn't necessarily support LACP - some do, some don't, but in general for most manufacturers it seems related to price and complexity.

I had a quick look at the next two PowerConnect models ( 3500 and 5400), and the data sheets for those specifically states LACP is supported.

formz1 · Answer

Ahh yes I see it now. Thanks.

Unfortunately, the dell switches that do support it are much more expensive than the ones that don't. :(

Oh well, I'll have to figure something out.

Thanks so much!

Matt

Fox350 · Answer

I did search to build a LAG between the Dell Powerconnet 2724 and a Cisco 4980-10G and did not find a lot of info else than this thread. I ended up making it work and the key is that Dell Powerconnect 2724 is LAG only, manual mode. There is no protocol supported for LAG negociation like LACP or Cisco propriatary Pagp. So the key is really to use channel-group 1 mode "on" to force a manual lag that do not try to negociate anything with the protocols. Here is my final configuration for a LAG, also TRUNK, all vlan's are transported :

port-channel load-balance src-dst-port

interface Port-channel1
description LAG Trunk vers DELL SW01 PWC2724
switchport
switchport trunk encapsulation dot1q
switchport mode trunk

interface GigabitEthernet1/45
description LAG Trunk vers DELL SW01 PWC2724
switchport trunk encapsulation dot1q
switchport mode trunk
channel-group 1 mode on
!
interface GigabitEthernet1/46
description LAG Trunk vers DELL SW01 PWC2724
switchport trunk encapsulation dot1q
switchport mode trunk
channel-group 1 mode on
!
interface GigabitEthernet1/47
description LAG Trunk vers DELL SW01 PWC2724
switchport trunk encapsulation dot1q
switchport mode trunk
channel-group 1 mode on
!
interface GigabitEthernet1/48
description LAG Trunk vers DELL SW01 PWC2724
switchport trunk encapsulation dot1q
switchport mode trunk
channel-group 1 mode on

Networking General

LAGs, VLANS, and Xserve

Was this post helpful?