Changing VLACP Mac Address...

[liamo]

I've been having problems with VLACP on a customer site over a metro ethernet link, and as part of the fault finding, it's been recommended to me to change the VLACP mac address from the default to 01-80-C2-00-00-06.

I've ran into issues, first of all disabling VLACP (in order to change the mac address). There's probably no 'proper' way to disable VLACP, but I disabled it at the core first (globally) which of course (as expected) resulted in all the edge switches bringing down the links because no more VLACP packets were appearing. (In hindsight, it would have been easier to disable on the edge, and resetting at the core, less stairs to take, but I need the exercise!).

My biggest problem was when I tried to re-enable the VLACP having made the MacAddress change. As soon as i enabled VLACP globally on the edge switch, it shut down the link immediately. I hadn't even got around to re-enabling on the core.

No combination of enabling VLACP on edge or core first resulted in a working link.

It was my understanding that the edge should be enabled first, as VLACP doesn't come into production until the edge sees the first VLACP packet from the core, at which point it's enabled and does it's thing.

It seems to me like the edge 'remembered' that it had seen a vlacp packet before, and because it's not seeing it now that it's disabled at the core, it shuts the link.

Network is setup as below:

2x 8606 Core running version 5.1 , IST with SMLT to the edge.
6x ERS 4548 stacks running version 5.2.2.013s
1x ERS 5520 Stack running version 6.1.0.0.7s

(5520 stack is across a MetroE link)


Anyone got any suggestions about what the hell I'm doing wrong?

(More details available on request!!)

Cheers,
Liam

[Michael McNamara]

Why did you change it? Was it conflicting with an address that was already in your network?

You changed the VLACP MAC address on all the switches, both core and edge?

If you want to work on VLACP you need to disable it at the port level. You should perform this work from the serial console so you don't get disconnected from the network interface. If you are physically connected to the core switch you need to disable VLACP (port level) on the edge first and then the core, albeit quickly though.

This is a case where you can saw off the branch your standing on. You just need to think it out and then plan accordingly.

Cheers!

[liamo]

Why am I changing the mac - it's a suggestion from Nortel TAC  .

Disabling using the serial is exactly what I did, but now I can't re-enable it without kicking myself off.

[Michael McNamara]

Hi Liam,

You changed the VLACP MAC address on all the switches, both core and edge?


Then confirm that you have VLACP enabled globally (on both switches - core and edge) and then enabled on the uplink (edge) and downlink (core) ports. I believe Nortel recommends short timers with 500ms and 5 retries for VLACP. If you issue a "show vlacp" the MAC address matches up both on the core and edge switches?

What do the logs say from the switches? I would suspect you haven't changed the VLACP MAC address on the edge switch although if you're getting directions from Nortel's TAC I would guess that they should have given you all the commands you need to run.

Good Luck

[liamo]

Yep, vlacp was changed both at the core and edge, the funny thing is that as soon as vlacp is enabled at the edge, (not at the core yet) the link goes down.

[Michael McNamara]

That's the correct behavior... the edge switch is not seeing the VLACP packets and is taking the port "out of service" (it does not admin-down the port). You need to enable VLACP at the ports on the core... if you are using short timers, 500ms, 5 retries that should give you 2.5 seconds (5 * 500ms = 2.5 seconds) to enable VLACP at the core port before the edge switch declares VLACP down.

That's why I mentioned that you might want to have out of band access (serial console / modem) to all 3 switches... and/or you need to plan out the configuration steps. If the workstation you are working from is cabled to the core switch then you should be able to change the edge switch and then quickly change the core switch. If you take longer than 2.5 seconds to change the core ports you are going to have an outage on your network. You realize that in an SMLT configuration you must change the VLACP parameters on both core ERS 8600 switches right? So you change the edge (this one change will change both ports in the MLT) then you must change core A and then core B.

I'm still curious as to why Nortel TAC suggested that you change the default VLACP address.

Good Luck!