VLANs Across Switches With LACP Trunks

[wtu]

Hi There,

I'm new to the HP Procurve world. Could anyone help me on configuring Procurve 2848 switches with VLANs across multiple switches and LACP trunks presence? I couldn't find any examples from manuals. Below is the situation:

There are three 2848 switches (A,B,C) with three VLANS (VLAN 1, VLAN 100, VLAN 200). A has four ports configured as LACP Trk1 connecting to B (as Dyn1 showing on B). B has two ports configured as LACP Trk2 connecting to C (as Dyn3 showing on C). The IP routing is enabled on A but not on B or C. Trunking ports are tagged.

Before I configured LACP trunking, routing and VLANs seemed to work fine since pinging from workstation on one VLAN to another workstation on another VLAN worked.

However, after I configured trunking, the pinging connectivity broke. Is there any examples? Thanks!

[Jody_Greene]

I would recommend not using LACP due to the fact that you are only using HP ProCurve switches.

Without seeing your configs, I would compare the below configs with yours.

Switch A
ip routing
interface 1
no lacp
interface 2
no lacp
interface 3
no lacp
interface 4
no lacp
trunk 1-4 Trk1 Trunk
vlan 1
tagged Trk1
ip address 1.1.1.1/24
exit
vlan 100
tagged Trk1
ip address 1.1.100.1/24
exit
vlan 200
tagged Trk1
ip address 1.1.200.1/24
exit

Switch B
ip default-gateway 1.1.1.1
interface 1
no lacp
interface 2
no lacp
interface 3
no lacp
interface 4
no lacp
interface 5
no lacp
interface 6
no lacp
trunk 1-4 Trk1 trunk
trunk 5-6 Trk2 trunk
vlan 1
tagged Trk1-Trk2
exit
vlan 100
tagged Trk1-Trk2
exit
vlan 200
tagged Trk1-Trk2
exit

Switch C
ip default-gateway 1.1.1.1
interface 1
no lacp
interface 2
no lacp
trunk 1-2 Trk1 Trunk
vlan 1
tagged Trk1
exit
vlan 100
tagged Trk1
exit
vlan 200
tagged Trk1
exit

[Matt Hobbs]

When configuring trunks, as Jody has suggested, it's best to configure them on both ends. You can use either 'trunk' or 'LACP' as the trunk type, as long as it's set on both ends.

With LACP configured as a static trunk on one end only, it will create a dynamic trunk on the other switch which can't be a member of multiple VLANs unless you configure GVRP (from memory).

[wtu]

Hi Jody,

Thank you for the prompt reply with the example and your valuable suggestion. Please refer to the attachment for the configurations on the three switches.

After I submitted the question, I found that my default gateway was specified wrong on one of the PCs used for testing. This caused the network connectivity to be lost. I used 192.168.20.3 and it should be always 192.168.20.1 for any devices connecting to VLAN 200. After I corrected the default gateway setting on that PC, the network connectivity was then restored.

There are two 3Com 3c17203 switches used for inter-building links using fibres. From one of the two switches, there is a port connecting to the Procurve 2848 switch which is currently in production. There are two Asante FM2900 switches used for another inter-building links. There exists a link between one of the FM2900 switches and the production 2848 switch. I'm configuring three new 2848 switches to upgrade the network. In order to avoid looping and accommodating switches only capable of doing 802.1d, could you make recommendations with examples? Although we don't have VLANs now, I would like to have VLANs configured to allow an upgrade in the near future.

Thanks!

[Matt Hobbs]

Do you have a network map that you could attached of what you'd what like to achieve?

From your configs, I'm assuming they're inteconnected via a few different ports, 33, 34, trunk1, trunk2.. if you could clarify this in the way of a network map it would really help.

When running with other devices that don't support 802.1w RSTP - you should set the interconnecting ports on the procurve to disable 'mcheck', and you should also change the port costs to match throughout the network. The spanning-tree chapter goes into more detail on this - ftp://ftp.hp.com/pub/networking/software/AdvTraff-Oct2005-59908853-Chap05-STP_RSTP.pdf

Most of the time though spanning-tree should figure itself out so you may not need to change anything at all, the above recommendations are really just that, recommendations.

[wtu]

Yes. They are interconnected with several trunk ports. Please refer to the simple drawing attached for the detail.

I've modified the configurations on the three new Procurve switches and used Procurve trunking but not LACP per Judy. Currently, there is only one Procurve 2848 switch with a flat subnet configured on it. I configured vlans across the three new switches with port trunking and would like to put these switches into production when the scheduled time comes. Then, I'll re-configure the cuurent production 2848. Additionally, I'll use SW1 as the new default gateway for servers, printers, and desktop computers (currently a Sonicwall firewall is being used as the default gateway). I'll also replace the Sonicwall with a CISCO ASA.

According to the current STP topology, the FM2900 SWA in building 3 is the root switch. FM2900 doesn't support RSTP. I'd like to use SW1 as the root switch instead.

Any ideas and/or recommendations? Thanks!

[Matt Hobbs · Accepted solution]

With your network map I can see your trunks between the 2848's. What I'd also do is have a single link going from the bottom 2848 back to the top 2848. That way if the middle switch dies, it's not going to completely isolate the one at the bottom.

There is a good chance though that the bottom switch may prefer this link to the trunk, so you may need to study spanning-tree priorities to make sure the links you wish to be blocked remain blocked in normal operation.

Also if you could include some extra links going to the second 2848 to the 3com and Cisco it would obviously help in the event that the top 2848 died.

This is all very paranoid of course, it's fairly rare that switches go faulty and if you can live with the possible downtime and move links manually in the event of a failure, then I would probably do that instead. (Keep it simple).

As for making your preferred swith the spanning-tree root, use the command 'spanning-tree priority 0'. That should do it, if not, you'll need to check the current root and give it a lower priority.

[jamesps]

Unless you want to monitor a trunk I would stay with LACP static. This gives you the advantage of customizing the STP parameters per trunk and also you can have the trunk operating in a different vlan other than the default one. This is extremely useful since you probably don't want to advertise the default vlan outside the switches own network. I would recommend creating vlans, IP them, dedicate management ports in that new vlan for management purposes then tag the ports accordingly. If you want to monitor a trunk then this option fails and you have to go with a "Trunk" type trunk.

In any case I would definetly leave all the ports with LACP ENABLED! This will detect, adjust and report any port/connectivity problem right away, LACP will block your port if something is wrong about it. Disabling LACP has no justification unless you want to avoid certain issues. It is a great feature you definetly want to use. If you decide to go with an LACP trunk or not that depends on your configuration and what you wish to achieve of course.

You can check the Management and Configuration guide there is a chapter which explains all about port trunking.

Hope this helps,
james

[wtu]

I really appreciate suggestions for establishing redundancies or HA by having additional links to the middle switch from the top and other switches located in other buildings. However, I decided to keep things simple at this stage without introducing potential spanning tree troubleshootings.

What I'd like to know is that if I run RSTP on the Procurve switches and STP is disabled while 3com and Asante FM2009 switches do not support RSTP, will I be able to use the command, spanning-tree priority 0, to force the top Procurve switch to act as the root bridge or I have to manipulate other paramenters on all switches to make it happen? What if the top switch acting as the default gateway fails, would there be a way for the middle or the bottom switch take over the default gateway IP originaaly assigned to VLAN 1 on the top switch?

Thanks!

[wtu]

I thought about creating another VLAN instead of advertising the default VLAN, VLAN 1, outside the switch's own network. However, if I do so, I have to create that VLAN on all other brand switches. They do not have layer 3 routing capabilities and are required to use an external router or a layer three switch for routing. In order to minimize modifications at this stage, I think it's better for me to live with a simple design for now and worry about others later on. I also thought about assigning VLAN 1 to every switch port as a tagged VLAN and then use it for port SPAN/mirroring purpose. Well, it could introduce too much change though.

I hesitate to make too much change now since I have been informed that, for some reasons, I won't be able to do console access to those switches located in other buildings at the time when I perform the network change because the change must be done outside regular hours and the buildings will not open then.

Does it make sense if I continue to use trunk type of trunks but create LACP type of trunks for redundancy in the future?

Thanks!