Switches, Hubs, and Modems
cancel
Showing results for 
Search instead for 
Did you mean: 

MSTP between two 2800 switches

Joris Deschacht
Occasional Advisor

MSTP between two 2800 switches

Hey,

I've got two 2824 switches with each two fiber SFP's.
port 21 SW1 -> port 21 SW2 (VLAN 2) - Uplink 1
port 22 SW1 -> port 22 SW2 (VLAN 3) - Uplink 2

So what I want do to is transport VLAN 2 over Uplink 1 en VLAN 3 over Uplink 2.
When I use standard RSTP offcourse port 22 SW2 is blocked.
So I thought to use MSTP, Am I correct this is a good way?

I configured this like below, but after everything port 22 SW2 stays blocked, what am I doing wrong?

SW1(config)# span protocol-version mstp
SW1(config)# write mem
SW1(config)# reload

• Define an MST region identity for the switch
SW1(config)# span config-name test
SW1(config)# span config-revision 1

• Associate user VLANs with MST instances
SW1(config)# span instance 1 vlan 2
SW1(config)# span instance 2 vlan 3


SW1(config)# span instance 1 pri 1
SW1(config)# span instance 2 pri 2
SW2(config)# span instance 2 pri 1
SW2(config)# span instance 1 p
10 REPLIES
raven_8
Frequent Advisor

Re: MSTP between two 2800 switches

Don't, you want to "trunk" these ports first, since they're piggy-backing? Might as well get the failover with teh added bandwidth if you can. look here in chapter 12: ftp://ftp.hp.com/pub/networking/software/59906023-1004-Management-Guide.pdf
Joris Deschacht
Occasional Advisor

Re: MSTP between two 2800 switches

Not really,

Because VLAN 3 has to be an exclusive uplink for synchronizing data between servers !!
(the servers have an extra network adapter for it)
So no other traffic can or may interfere!

Cheers,
raven_8
Frequent Advisor

Re: MSTP between two 2800 switches

I'm not understanding. If VLAN 3 has to be isolated, then you wouldn't be able to run it across the switches to begin with. you'd be running cross-over cables end-to-end or a seperate switch/hub.

I think the reason this isn't working is because you're really creating a network bridge. Except you're trying to do some funky stuff with VLAN'ing to try to make it work.

So, I think Spanning Tree is disabling your second connection. Even though you have VLAN's to manage the traffic, switches were never meant to do that, VLANS aren't supposed to get that complex (to the point where they're limiting all traffic) I think a VLAN see's broadcasts from both networks (I could be wrong here). So if this did work, you'd criple those uplinks in a heartbeat from broadcast storms.

I'll be the first to say that networking isn't my forte, but I know a little, and I don't think this can or will work without a router segmenting the networks.

Heh, but then again, I don't even know what MSTP or RSTP are.
Joris Deschacht
Occasional Advisor

Re: MSTP between two 2800 switches

MST enables administrators to configure redundant links without sacrificing
capacity, as is sometimes necessary with STP and RSTP. This is true because, in
MST, Spanning Trees are associated with VLANs, not with physical links. The
Spanning Tree state of a link can vary according to the local topology of any MST
instance.

Allows VLANs to be assigned to different Spanning Tree instances that
independently select the lowest cost path through the bridged network
raven_8
Frequent Advisor

Re: MSTP between two 2800 switches

Maybe I'm a purist, but isn't that what the router is supposed to do? Though I guess the router doesn't play with VLANs.... Neat feature. Your redundant link should only work with a loss of link (since that's the only state a switch should be aware of). In your testing, did you pull the primary? If so, how long was it out? Remember, this is spanning tree, not real routed links. So your spanning tree will need to renegotiate, so if that's not out a good couple of seconds, I don't think your network will have the time it needs to re-route.

Your testing will cause packet loss, but if it's set up right, it shouldn't take too long.
Joris Deschacht
Occasional Advisor

Re: MSTP between two 2800 switches

This has nothing to do with routing !!!
MSTP you can see as a separate spanning tree per VLAN, so no routing involved, just a STP for each VLAN.

Nobody here played or had MSTP running ??

Cheers,
Kell van Daal
Respected Contributor

Re: MSTP between two 2800 switches

Use MSTP only if you need uplink 1 to also be the backup for uplink 2 and vice versa.

Maybe you just forgot to paste it here, but I see you configuring SW1 parameters, but not all SW2 parameters. Make sure the config-name and config-revision are the same.
And also the VID -> instance assignments are the same.
I also don't see the actual enabling of spanningtree with the global command: SW1/2(config)spanning-tree

You also need to configure both ports in both switches to VLAN 2 and 3.

Another possible way you could consider is trunking the two uplinks, and use QOS to make sure VLAN 3 gets higher priority.
Joris Deschacht
Occasional Advisor

Re: MSTP between two 2800 switches

Config for SW2 is indeed not entirely passed, but everything you suggest is configured, als MSTP is actived with the correct config.
All I want is that uplink 1 is dedicated for VLAN 2 en nothing else and uplink 2 is dedicated for VLAN 3. But off course won't interfere with eacht other on STP level.

regards,

raven_8
Frequent Advisor

Re: MSTP between two 2800 switches

Dude...
A seperate spanning-tree for each VLAN???!!! Sorry, my mind stops just before comprehending that. I wish I could help you more.
Regnar Bang Lyngsø_2
Frequent Advisor

Re: MSTP between two 2800 switches

Just one more thought,

all VLANs defined on SW1 are defined on SW2 and vice versa?

What does a 'show spanning-tree' give you (have SW1 and SW2 agreed on the root and so on)?

Regnar
--
Favourite bugs this month:
http://www.columbia.edu/~alan/igmp/
http://www-307.ibm.com/pc/support/site.wss/document.do?lndocid=MIGR-57879
http://www.vmware.com/support/kb/enduser/std_adp.php?p_faqid=1549