Ethernet LAN STP, VLANs redundant router problem

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Subject Author Date
STP, VLANs redundant router problem BCCS 01-08-06
Posted by BCCS on January 8, 2006, 8:13 am
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I have a fully redundant network that is being migrated from an externally
managed Cisco network to an internally managed network.

We have three Dell 5324's and two firewalls that failover

For the sake of simplicity I'll refer to them as 5324.1, 5324.2 & 5324.3.
When a specific is referenced, I'll add it to the end of the name (i.e.
5324.1.23 = 1st 5324, port 23).

All 5324's have the following in common:

VLAN 20 = WAN, ports g1-4 - 200.x.x.x

VLAN 30 = DMZ, ports g5-10 - 20.x.x.x

VLAN 40 = LAN, ports g11-23 - 2.x.x.x

All have default gateway set to 2.x.x.3

No IP address is assigned to the WAN VLAN

The DMZ VLAN is assigned an address

The LAN VLAN is assigned an address



Both routers have WAN, DMZ, LAN and failover interfaces

Both routers have the following in common:

Port 0 = WAN - 200.x.x.x

Port 1 = DMZ - 20.x.x.x

Port 2 = LAN - 2.x.x.x

The failover allows for a virtual IP address on the LAN and WAN interfaces.



I'll refer to the Routers and their ports are follows:

RTR.1.2 = 1st Router, port 2 (or LAN)



WAN (VLAN) connections

RTR.1.0 - 5324.1.1 - 200.x.x.1

RTR.2.0 - 5324.3.1 - 200.x.x.2

Virtual IP -200.x.x.3



DMZ (VLAN) Connections

RTR.1.1 - 5324.1.5 - 20.x.x.1

RTR.2.1 - 5324.3.5 - 20.x.x.2



LAN (VLAN) Connections

RTR.1.2 - 5324.1.11 - 2.x.x.1

RTR.2.2 - 5324.2.11 - 2.x.x.2

Virtual IP - 2.x.x.3



STP (Rapid) Configuration

5324.1.21 - 5324.2.21 (root bridge priority 4096)

5324.2.22 - 5324.3.22 (bridge priority 8192)

5324.1.23 - 5324.3.23 (bridge priority 32768)



None of the 5324's show that any STP or blocking.



The root bridge shows FRW, Desg status on 1.21 & 1.23

The bridge with priority 8192 shows 2.21 as FRD, Root & 2.22 as FRW, Desg

The bridge with priority 32768 shows 3.22 as DSCR, Altn & 3.23 as FRW, Root



Now for the problem:

The default gateway for all 5324's is the Virtual LAN IP of the routers. I
can ping from any 5324 LAN IP address to any other of the 5324 LAN IP
addresses. I can ping also the DMZ interface from 5324.1, but not the other
two (.2 &.3). All switches can ping out to the internet and can use DNS for
name resolution.

A device plugged into a DMZ port on 5324.1 can not access other devices with
the DMZ VLAN but connected to one of the other 5324's.



I'm sure in all the detail I'm missing a simple problem, but.

Any thoughts are appreciated!!






Posted by anoop on January 8, 2006, 4:55 pm
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BCCS wrote:

[..]

> A device plugged into a DMZ port on 5324.1 can not access other devices with
> the DMZ VLAN but connected to one of the other 5324's.

>From your description it's hard to see how things are wired so
it's near impossible to tell why it's not working. Not being able
to ping from a DMZ device on one switch to a DMZ device
on another switch is weird because there should be no router
involved. However, this is dependent on there being a switched
path between that VLAN on all of your switches.

Anoop



Posted by BCCS on January 9, 2006, 12:05 pm
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anoop wrote:
> BCCS wrote:
>
> [..]
>
> > A device plugged into a DMZ port on 5324.1 can not access other devices with
> > the DMZ VLAN but connected to one of the other 5324's.
>
> >From your description it's hard to see how things are wired so
> it's near impossible to tell why it's not working. Not being able
> to ping from a DMZ device on one switch to a DMZ device
> on another switch is weird because there should be no router
> involved. However, this is dependent on there being a switched
> path between that VLAN on all of your switches.
>
> Anoop

Anoop,

Thanks for the reply. I'm sorry it wasn't more clear. I was trying to
give as clear as possible overview that contains a lot of info.

There's one patch cable from switch 1 to switch 2, 1 cable from switch
2 to switch 3 and one cable from switch 1 to switch 3. All
inter-connects are connected using ports that are members of the LAN
VLAN. If I connect cables from switch to switch within the other
VLANs, STP will block the redundant connections as the Dell 5324's do
not support per VLAN STP.

Does that clarify?

Again, thanks for the help!

- B



Posted by anoop on January 9, 2006, 8:20 pm
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BCCS wrote:

> There's one patch cable from switch 1 to switch 2, 1 cable from switch
> 2 to switch 3 and one cable from switch 1 to switch 3. All
> inter-connects are connected using ports that are members of the LAN
> VLAN. If I connect cables from switch to switch within the other
> VLANs, STP will block the redundant connections as the Dell 5324's do
> not support per VLAN STP.

Based on what you write, there's a loop so at least one of the
switches should have a port that is blocked by STP.

Also, what is the connectivity between the switches for the DMZ
vlan? You were trying to get your ping from a DMZ device on one
switch to a DMZ device on another switch. There has to be a
switched path for that VLAN that spans all the switches.

Anoop



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