Expanding an HP IRF topology

hp-procurveredundancy

I'm examining options for a future expansion of our infrastructure. We rent space at a colo so we don't have a dedicated datacenter of our own. This means that our next major expansion will likely involve two discrete cages not immediately adjacent. I'm looking at ways of bringing my network into a new cage.

Our current topology has a pair of HP A5820's in an IRF pair, and all of our distribution switches linked to both routers through a 10Gb BAG/Trunk port. That's all well and good.

The question I have comes when we add another full cage. The way I see it, I have two major options:

Continue as I am, and connect the distribution switches back to the pair I already have.
Pick up another pair of A5820's and connect the new cage's distribution switches to that, and link that pair to the pair I already have somehow.

It's the second option that I'm getting some confusion with.

IRF - linear topo

This is a pretty standard topology, in that I link the new switches back to the other pair in a linear topology. Anything in Cage 2 needing to go to the other switch will have to transit the full stack, though. I know this will work.

The question here is, can I short-circuit that with a ring topology? Does IRF allow that?

IRF - ring topo

This would allow a shorter transit of packets. That said, I don't know if IRF allows this kind of setup. If it doesn't…

Paired IRF with trunks

Or I could create a second IRF device in the new cage, and link the two together with aggregation ports and not bother with IRF at all between them.

Considering each cage would have all of my distribution switches connected to both pairs, the IRF links may not actually get that much traffic across them. If so, I'm over-thinking this.

Am I over thinking it? And if not, does IRF allow a ring topology?

Best Answer

I'm not HP savvy but I did some quick Googling (hp irf ring topology) and found a couple of docs that indicate it does support a ring topology.

c02648772.pdf

Quote from page 5:

IRF topologies

Create an IRF virtual device in daisy chain topology, or more reliably, ring topology, as shown in Figure 2. In ring chain topology, the failure of one IRF link does not cause the IRF virtual device to split as in daisy chain topology. Rather, the IRF virtual device changes to a daisy chain topology without affecting network services.

This page has the same quote so at least that seems like a possibility.

HP seems to be recommending the ring but beyond that I can't speak to HP gear.

Related Solutions

Routing – Reconfiguring Layer3 Switch to enable IP routing and become the default gateway

I tried to upload a visio picture that shows what I think you are trying to accomplish, but I guess I need more reputation! You basically need to enable IP routing on the HP switch that will be the gateway, and add a default route. I definitely recommend using separate VLANs for your different networks. You will also need to make sure that your ISP router has a route back to your HP switch for your 192.168.1.0/24 network:

ISP Router

Int fa0/0    
Ip address X.X.X.1 255.255.255.252    
Ip route 192.168.1.0 255.255.255.0 X.X.X.2

HP Switch 1

Ip routing  
Vlan 10 name ISP  
Ip address X.X.X.2 255.255.255.252  
Untagged 1  
Vlan 20 name LAN  
Ip address 192.168.1.1 255.255.255.0  
Untagged 2-48  
Ip route 0.0.0.0 0.0.0.0 X.X.X.1

HP Switch 2

Ip default-gateway 192.168.1.1  
Vlan 20 name LAN  
Ip address 192.168.1.2 255.255.255.0  
Untagged 1-48

In and Outbound Dual VRRP connections

This is the logical view of what you're trying to achieve:

Dual VRRP Logical Architecture

Configure the router priorities for both VRRP 'a' and VRRP 'b' as follows:

Router 1: 110 (master)
Router 2: 100 (backup)

The configure interface tracking as follows:

Router 1 VRRP a: track interface R1b with a track priority of 90
Router 1 VRRP b: track interface R1a with a track priority of 90
Router 2 VRRP a: track interface R2b with a track priority of 90
Router 2 VRRP b: track interface R2a with a track priority of 90

If interface R1b goes down, Router 1 will change its VRRP 'a' priority to 90. This priority is now less than the VRRP 'a' priority that Router 2 has, so it will preempt and take over mastership for VRRP 'a'.

In addition, because interface R1b has gone down, then the VRRP hello packets will fail across VLAN 'b'. This will be detected by Router 2 (after failing to receive a hello packet within the dead timer interval), at which point it will take over mastership for VRRP 'b'.

If interface R1a goes down, then in a similar fashion, Router 2 will take over mastership for both VRRP groups (Router 1 VRRP 'b' priority = 90, and the VRRP hello packets will fail across VLAN 'a').

If either interface R2a or R2b goes down, then Router 1 will continue to be master for both VRRP groups.

Note that the priority value I've chosen above are quite arbitrary -- you may want to choose different values. Also, if the VIP address of a particular VRRP group is the same as the interface address for one of the routers in that VRRP group, then that router will automatically take a priority of 255 (i.e. it will always be the master unless that interface goes down).

As a side note, to get the above logical architecture, you will need a physical architecture similar to the following:

Dual VRRP Physical Architecture