Routing and Stacking Procurve 2910al's...

[Gavin Williams ACT]

HI there,

We are in the process of configuring 3 2910al-24's in a new deployment as our core network stack.

We've configured the 3 switches as follows:
Switch 1 - Default gateway for all devices:
Default VLAN (ID 1) - Ports 1-4, IP 10.0.31.254
DMZ VLAN (ID 2) - Ports 1-2 & 13-20, IP 172.16.31.254
Proxy-ARP is enabled on both VLANs.

Switch 2:
Default VLAN (ID 1) - Ports 1-4, IP 10.0.31.253
DMZ VLAN (ID 2) - Ports 1-2 & 13-20, IP none

Switch 3:
Default VLAN (ID 1) - Ports 1-4, IP 10.0.31.252
DMZ VLAN (ID 2) - Ports 1-2 & 13-20, IP none

All are part of the same stack, with switch1 as the commander.

Spanning tree and IP Routing are enabled on all 3 switches.

All 3 switches are then cascaded together using standard Cat 5e cables in ports 1-4.

However we're having issues with a couple of points...
1) How to route between subnets - even with 1 device in each VLAN on switch 1... All I keep getting is "Net not found" when trying to ping across the VLANs...

2) How to keep working even if switch 1 - the default gateway for most devices - dies?

I've read through the various manuals and cant find anything obvious...

Any ideas?

Cheers
Gavin

[Drew Redman]

1) All that is needed to route between your directly connected vlans, is to have IP Routing enabled on the switch and an IP address on each vlan that you are routing on. You don't need to have routing enabled on all switches. The preferred method is to pass all of your vlans at layer 2 to the routing switch and then use the appropriate vlan address as your default gateway for each device in that subnet.

2) Spanning tree and VRRP will accomplish this. Your topology might need to be changed, as a cascading topology doesn't do well when a switch goes down.

Have a look at the advanced traffic guide for the 2910al on procurve.com if you haven't already.

You should consider configuring ports 1-4 into trunks for higher capacity and availability. I assume they are all connected right now and STP is blocking 3 of the links.

Lastly, stacking is only for management purposes. It was designed for IP address conservation. It does not create any sort of tunnel for vlans to pass between the switches, you'll still need to configure your vlan port membership for that. Stacking only allows you to manage several switches with a single IP. Since you're routing, you'll need to use several IP's anyway.

[Pieter 't Hart]

stacking procurve is only for centralized management.
It's not comparable to cisco 3750 stacks where a stack acts as a single switch.

so you still need to configure the links between the stack-members to pass all necessary vlan's.

like switch1-port23 connects to switch2-port24 and switch-2-port24 to switch3-port24

! then on switch-1 (I ommit the client ports)
vlan1
untagged 23,24
vlan 2
tagged 23,24
! on switch2
vlan1
untagged 24
vlan 2
tagged 24
! on switch2
vlan1
untagged 24
vlan 2
tagged 24


! configure Switch1 for routing
vlan1
ip address 10.0.31.254 255.255.255.0
vlan2
ip address 172.16.31.254 255.255.255.0
ip routing
ip route 0.0.0.0 0.0.0.0 10.0.31.1 (external router if necessary)

clients in vlan1 have default gateway 10.0.31.254
clients in vlan2 have default gateway 172.16.31.254
external router must have static route
ip route 172.16.31.0 255.255.255.0 172.16.31.254