Port - Channel

[mmendis]

Hello All,

I'm trying to connect following attached setup using port channeling. Can someone help me here , whether this setup is possible with Port-Channeling ???

[Bram Van den Bosch]

What switches are you using?

In general you can't connect a single port channel across multiple switches.

However, you can use stacking, VSS or vPC if your switches support it, to accomplish a port channel accross 2 switches.

[mmendis]

Cisco 3560 ......

[Bram Van den Bosch]

The 3560 does not support stacking, VSS or VPc.

These 3 technologies make 2 or more switches appear as 1 logical entity (to some extend), all 3 work differently and are supported on different models. One thing that they allow to do, and is in fact very common is to create a portchannel on 2 different swicthes (in the same stack, VSS or VPc) to allow redundancy on a loop free manner.

Since you are talking about 3560 and a router you might be able to do 2 thins:

- use STP (if the router has an integrated switch module), when using this there will always be one link blocked.

- use routing, this way you can create a topology that can take use of both links, you can use a routing protocol (depending on the license on the 3560)

[mmendis]

Thanks mate !!!!

Please refer above 2 diagrams ..... I can't use routing ... high availability should happen from Layer2 ....

Any ideas ????

[Seb Rupik]

Hi there,

Looking at your diagram you will need three different portchannels, it depends on whether you are using newer Nexus switches (which use vPC) or Catalyst switches (using VSS).

In the Nexus solution:

Router to L3 switches :  vPC

Between L3 switches: vPC peer-link

L3 switch to server: PortChannel

Catalyst solution:

Router to L3 switches: MEC

Between L3 switches: VSL

L3 switch to server: PortChannel

For each of the three line items above you would refenence them induvidually, and not a a single channel '1' as you have done in your diagram.

cheers,

Seb.

[mmendis]

Is this possible with Cisco 3560 ????

[Seb Rupik]

The 3560 does not support VSS. If you wanted to keep your topology you would need to rely on STP to allow redundancy.

The links from the router to the 3560's could be PortChannels but your would need two of them, each termintated on a different 3560. STP would determine which link was forwarding and which was was blocking.

The link between the 3560 would be an ordinary PortChannel trunk link.

The link to the server would also be an ordinary PortChannel.

cheers,

Seb.

[mmendis]

Thanks mate !!!!

Could you please the solution you have proposed, i'm bit confused ?

[Seb Rupik]

See attached.

3560-A has PortChannels Po1, Po3, Po4 configured.

3560-B has PortChannels Po2,Po3 configured

Make sense?

cheers,

Seb.

[mmendis]

Thanks !!!!

Now it make sense .....

Currently I have following setup

A,B&C are my upstream providers -> connecting to CSWT1 & CSWT2 -> R1 & R2 are ASR 1002 & ASR1001 ( 4 ports each ) -> connect to SWT 1 & SWT 2

I want to increase it's high availability like above. That's why I thought of using port channeling.

Any Ideas ?????

[Seb Rupik]

If your two ASRs only have four ports, how are you going to achieve your second design? You need an additional line card.

I would suggest that you use routed links between the each switch and the ASR's, and for each VLAN running from the switch to the ASR's run a GLBP process on the ASR's. This would add gateway resiliency at the same time as providing two forwarding paths.

cheers,

Seb.

[mmendis]

R1 & R2 will only needed 4 connections ( as per the diagram )

Will GLBP setup going to change my existing IP address setup ????

[Seb Rupik]

...but you said you wanted PortChannels :

CWST1 -> R1 = 2 links

R1 -> SWT1 = 2 links

...if you want to add any further cross-links you have no more free ports.

If you scrap the idea of PortChannels going to the ASRs and just between your switches, then you'll have enough ports.

Running GLBP will require an additonal IP (for the VIP), so you will have 3 gateway IPs per VLAN.

cheers,

Seb.

[mmendis]

Thanks Seb, thanks for the suggestion !!!!!

I'm not familiar with GLBP but now i'm testing it ....

Meanwhile could you please check my same setup with following devices.... ??

Will it work ???