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HP 5130 3x IRF switch loop + MAD ARP

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Futurity
Occasional Contributor

HP 5130 3x IRF switch loop + MAD ARP

Hi,

I have an IRF fabric made up of 3x HP 5130 switches connected together via their SPF+ ports.  

There are 3x Ten Gigabit SPF+ cables connecting them together:

A to B

B to C

C to A

If I was to loose a single cable or a single switch, am I correct in thinking that there wouldn't be a split stack as the remaining two switches would still have a direct SPF+ cable between them to keep the IRF fabic intact?

If I were to loose 2x SPF+ cables (or a single switch + a single SPF+ cable), this would cause a split stack. To handle this I've configured MAD ARP using dedicated chained gigabit ports in the arrangement:

A to B

B to C

If switch B went offline, then this chained MAD ARP topology would fail.

Does anyone know if it is possible to create MAD ARP with a loop topology as in the arrangement:

A to B

B to C

C to A

This would cope with a switch + cable failure, but would it cause a loop to be detected?

Thanks for any help you may be able to provide,

Neil

8 REPLIES
Linkk
Frequent Advisor

Re: HP 5130 3x IRF switch loop + MAD ARP

Hi Futurity,

ARP MAD can work with or without a direct link between the IRF members. Every member should get the extended ARP packets of the other IRF, notice that a split has happened and one will shut down. 
Also Spanning Tree is mandatory for this scenario, so that no loop can occur.

The other possibilities, maybe easier, are LACP MAD and BFD MAD. 
With LACP MAD you have to have an independent HP switch, which supports LACP MAD and is connected to every IRF member. This switch will see the split happening and will send the shutdown command to the IRF with the higher active ID.

With BFD you connect every member with every member, which can take quite a lot interfaces in a bigger scenario.

Please refer to the 5130 IRF guide for more details:
http://h20566.www2.hpe.com/hpsc/doc/public/display?sp4ts.oid=7399420&docLocale=en_US&docId=emr_na-c04771708

 

Futurity
Occasional Contributor

Re: HP 5130 3x IRF switch loop + MAD ARP

Hi Linkk,

Thanks for your reply.  I really appreciate it.

So the simplest solution appears to be ARP MAD with all 3x IRF switches directly together in a loop, but with Spanning Tree enabled to prevent a network loop?

The alternative is LACP MAD or BFD MAD:

I have 2 seperate IRF domains (each consisting of 3x HP IRF switches).  The older IRF domain 0 is for core network traffic between servers and the new IRF domain 1 is used for edge devices (desktops / laptops / etc).

The next best switches I have are HP 2824 switches which I don't think supports any type of MAD?  This is a shame as they would have been ideal for MAD support.

However, the 2 seperate IRF domains are connected together via a "10 seperate Gbps cables", combined into a single Bridge Aggregate (LACP) over which all the traffic flows from one domain to the other (many different VLANS used for desktops and servers).  

The current MAD ARP use different VLAN numbers (domains 0's MAD ARP VLAN is different from domain 1's MAD ARP) and both VLANs are currently local only.

I'm wondering if each domain could act as the remote LACP / BFD MAD switch for the other domain?  

Ideally I'd like to use the existing bridge aggregate if possible to eliminate the need to use dedicated Gigabit ports for this purpose.

If I turn off the MAD ARP and permit the two VLANs across the Bridge Aggregate, could I use these VLANs for LACP MAD or BFD MAD, bouncing the MAD packets off of the other IRF domain switches?

Thanks again for your help,

Neil

 

 

 

 

parnassus
Honored Contributor

Re: HP 5130 3x IRF switch loop + MAD ARP


Futurity wrote: The next best switches I have are HP 2824 switches which I don't think supports any type of MAD?  This is a shame as they would have been ideal for MAD support.

Exactly, the HP ProCurve 2824 doesn't support LACP MAD so it can't be used to act as MAD device.

An Aruba 2920, as example, could be a good switch (it supports LACP MAD) to be used to act as a single MAD device respectively for your two IRF Domains.

Futurity
Occasional Contributor

Re: HP 5130 3x IRF switch loop + MAD ARP

Hi Parnassus,

Thanks for your quick reply and the recommendation of the Aruba 2920 switch.  I'd rather not by additional hardware if I can help it as we have very limited space in the cabinet.

Do you know if I can use the IRF Domain 1 as the LACP MAD switch for IRF Domain 0 and vice versa?  I don't mind dedicating some ports if necessary.

Neil

parnassus
Honored Contributor

Re: HP 5130 3x IRF switch loop + MAD ARP


Futurity wrote: Do you know if I can use the IRF Domain 1 as the LACP MAD switch for IRF Domain 0 and vice versa?  I don't mind dedicating some ports if necessary.

Hello Neil, I haven't an extensive experience about LACP-MAD *but*, AFAIK, since deploying LACP-MAD between an IRF Domain and a 3rd party (LACP-MAD enabled) MAD device requires that a pretty standard LACP Port Trunk is defined between both logical ends (so on IRF side, Member 1, 2, 3 and so on...and on the MAD device side) and, once that is done, it also requires that MAD feature is enabled on that dedicated Port Trunk created on both sides (Note: if the MAD device is a ProCurve based instead of being Comware based the Port Trunk option to be enabled will be simply "mad-passthrough enable", if the MAD device is a Comware based that option became simply "mad enable", IRF side the Port Trunk option is clearly "mad enable" on the Port Trunk dedicated to LACP-MAD)...I think that you will end up with a Loop since you *already have* a Port Trunk set up between your two IRF Domains (I mean that that additional LACP-MAD Port Trunk set up between IRF Domain 0 and IRF Domain 1 would loop with the one you already have)...I hope to be wrong so you can accomodate without using an external (to your IRF Domains) intermediate device...OTOH MAD Device seems to imply it needs to be something totally external to the IRF Domain for which it acts as MAD Device...

Futurity
Occasional Contributor

Re: HP 5130 3x IRF switch loop + MAD ARP

Hi Parnassus,

I see your point.  I guess that it might work if I had two additional LACP dedicated trunks between the 2 IRF domains:

Trunk 1: normal inter IRF domain traffic

Trunk 2: dedicated for domain 0 LACP MAD

Trunk 3: dedicated for domain 1 LACP MAD

Even if this works, the problem is the number of ports it would require.  

For Trunk 2 is would need a port from each switch member of IRF domain 0 connected to ports on IRF domain 1 (3 + 3 ports)

and for Trunk 3 is would need a port from each switch member of IRF domain 1 connected to ports on IRF domain 0 (3 + 3 ports).  

So 12 ports in total.

Comparing this with configuring MAD ARP directly within each IRF domain, using "stp enable" to prevent loops, this would require 2 ports on each switch in orfer to create the loop. Domain 0 (2 * 3) + Domain 1 (2 * 3) = 12 ports in total.

Which option is best, MAD ARP or LACP ARP? MAD ARP seems easier to configure but are their disadvantages?

Sorry for all these questions and I hope these answers prove useful to others.

Neil

parnassus
Honored Contributor
Solution

Re: HP 5130 3x IRF switch loop + MAD ARP

The point is that (I fear) those two additional LACP dedicated Trunks between your two IRF Domains (Trunk 2 and Trunk 3) will form a nasty loop with your inter-IRF Domains existing Trunk (Trunk 1).

IMHO LACP MAD with a third party Switch (HPE Comware or Aruba ArubaOS-Switch operating system or anyother Switch which is able to support LACP MAD) is the way to go: 3 Ports aggregated on a LACP MAD enabled Port Trunk on IRF Domain 0 fabrics (distributed across your three IRF Members), 3 other Ports aggregated on a LACP MAD enabled Port Trunk on IRF Domain 1 fabrics (distributed across your three IRF Members) and 3+3 (total of 6) equivalent ports aggregated in two Port Trunks on the MAD intermediate device.

Yes, you will be forced to use additional Hardware but, that way, from the point of view of each IRF stack, you are you dedicating three ports per IRF Domain to LACP MAD (I expect that IRF ports are more "valuable" that corresponding ports used on the MAD intermediate device).

MAD techniques comparison:

MAD_approaches_comparison.png

 I'm not totally sure that the statement "Requires no dedicated physical ports or interfaces" under LACP MAD Advantages column is correct...moreover use HPE or Aruba insteal of H3C (the screenshot was taken from an H3C document).

 

 

 

Futurity
Occasional Contributor

Re: HP 5130 3x IRF switch loop + MAD ARP

Thanks for your answers and recommendations.

I really appreciate it.

Neil