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Author Topic: ERS 5510 LACP & VLANs  (Read 3817 times)

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Offline stevenahmet

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ERS 5510 LACP & VLANs
« on: April 26, 2015, 11:23:55 PM »
Hi,

We've got 2 stacks of ERS 5510-48T's.
One stack, consisting of 5 switches, is located on Level 5.
The other stack, consisting of 2 switches, is located on Level 6.
They are trunked together by MLT. Spanning tree is disabled on the MLT.
This trunk carries tagged VLANs for 1, 10 & 20.

Spanning tree is enabled on the other ports. At the moment, it's just the default spanning tree. It's not RTSP or anything.

I need to create another link from L6 to L5. This link will be carrying tagged VLANs of 30 & 40, and have a PVID of 50.

So what's going to happen when I connect this link? I need both of them to be active as they're for different purposes. Do I need to create spanning tree groups and have this second link as members of the the new group?

A different but related question;

I want the switch stack on Level 5 to be the root bridge. If I look at both switch stacks, they both have a "Bridge Priority" of 8000. Should just lowering the "Bridge Priority" on the Level 5 stack accomplish this?

Anything else I need to be wary of?

Let me know if I need to provide any other info.
Thanks.

Steve


Offline stevenahmet

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Re: ERS 5510 LACP & VLANs
« Reply #1 on: April 27, 2015, 12:26:50 AM »
Just realised that the title of my post might be misleading as I'm not dealing with LACP in this case.
I was dealing with this regarding something else today, so must've typed it subconsciously.

But in regards to these 2 stacks connected via MLT;

I can see via the show spanning-tree config command, that the base unit, switch 1, in the Level 5 stack is the Root Bridge.

But if I do the same command on the Level 6 stack, I can see that the base unit is also the root bridge of that stack.

Is this a problem? Or is it the fact that spanning tree is disabled on the MLT that these 2 disparate root bridges exist?

Thanks.

Offline stevenahmet

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Re: ERS 5510 LACP & VLANs
« Reply #2 on: April 28, 2015, 02:18:42 AM »
Still hoping I can get some answers here;

Can I step back and get a couple of questions answered?

1) I read somewhere that it was recommended to turn off spanning tree for an MLT. Is this true?

2) So lets say I have 2 switches connected together. One connection is through an MLT with spanning tree ON, (if it's recommended in my case to have it turned on). It's carrying VLANs 1 (native), 10 (tagged) and 20 (tagged).

I then want to connect these 2 switches by another link carrying VLANs 30 (tagged), 40 (tagged) and 50 (untagged/native).

Is spanning tree going to automatically create per vlan spanning tree or will it just block one of the links between the 2 switches?

I've simulated this on Cisco switches in Packet Tracer.
- I put 2 switches in.
- I connect them together through a crossover cable on port 1.
- I attach 2 PC's (one off each switch) and give them IP addresses in the same subnet.
- PC's can ping each other.
- I then connect the 2 switches via a second crossover cable on port 2.
- Immediately spanning tree kicks in and blocks port 2.
- I then make port 2 on both switches trunk ports and assign them to VLANS 10 (native), 20 & 30.
- I connect another 2 PC's and give them IPs in a different subnet. The ports they are connected to are access ports, and are members of VLAN 10.
- The links across the switch are all active. PC's can ping each other on the same subnet, but not on different subnets.
- When I look at the spanning tree config, it breaks it down on a per vlan basis and works as I would want.

Is this similar to what would happen on the ERS 5510 or is there other config I would need to do?
Thanks.

Offline Dominik

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Re: ERS 5510 LACP & VLANs
« Reply #3 on: April 28, 2015, 02:40:29 AM »
Hi  stevenahmet,

the first question is why do you want a second connection besides your exsisting MLT ?
The normal approach would be to configure the additional VLANs 30, 40 and 50 to your exsisting MLT.
If you need more bandwith you can scale up your MLT up to 8 links that connect your two stacks with each other.

You can run STP across your MLT for loopprotection of additional linksbetween the two stacks.

Cheers
Itīs always the networks fault!
networkautobahn.com

Offline stevenahmet

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Re: ERS 5510 LACP & VLANs
« Reply #4 on: April 28, 2015, 06:14:18 PM »
I need a second connection because I've got wireless access points that I need to run between floors (switches). The reasons I want it to be on that second connection are;

1) I've got my main network including DHCP running on VLAN 1 and is the PVID on that first MLT.

2) My wireless AP's need to obtain a DHCP address from somewhere before they become active. I could let them get an IP address from my DHCP server on VLAN 1, but as I mentioned, I want to keep the wireless network separate and I don't want broadcasts from everything on VLAN1 on the wireless.

So this means I need a second connection between the switches to carry one untagged PVID (50), and I also need 2 tagged VLANS (30 & 40) for my staff and guest wireless SSID's.

Offline Dominik

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Re: ERS 5510 LACP & VLANs
« Reply #5 on: April 29, 2015, 08:35:31 AM »
It is no problem to transport the DHCP packets across a tegged link between your two switches. You only need an untagged DHCP packet for your APs on the accessports to that the APs are connected.

So make the link between the two switches a tagAll link with the needed VLAN Ids. There is no need for your usecase to have a second link.
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Offline stevenahmet

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Re: ERS 5510 LACP & VLANs
« Reply #6 on: April 29, 2015, 05:47:16 PM »
Thanks Dominik. Makes sense. I'll give that a try.

**Edit: Yup, that works. Thanks again.
« Last Edit: April 29, 2015, 06:34:07 PM by stevenahmet »