Cisco Etherchannel – Link Aggregation Between Two Switches with Intermediate Switch

ciscoetherchannelswitch

I have 3 switches soon to be setup in topology as shown below

I have a fibre link and LAN cable directly connecting switch1 and switch3 and also another connection going from switch1 to switch3 via switch2 using LAN cables.

I want to have Link Aggregation Group(LAG) at switch1 for the 3 ports (2 directly connecting to switch3 and one through intermediate switch2) for getting higher bandwidth and failover redundancy for switch3.

Q1- Is it possible to have LAG with the indirect connection through switch2 as shown in the figure?

Q2- How would I configure LAG for ports @ switch1? (If you point me to exact commands or any resources links, it would be helpful)

Q3- Do I need to configure LAG @ switch3 also for corresponding ports?

Q4- What modes(active/passive/on) should I use for LACP @ switch1 and @switch3?

Best Answer

Q1: This requires MLAG (multichassis LACP) to work. You can't split and splice a simple static or LACP trunk.

Q2: As far as I know, SG500X and SG300 don't support MLAG. You can configure a LAG trunk for the two lines between S1 and S3 though and use STP(Spanning Tree Protocol) to take care of the looping links to S2.

Q3: LAG trunks need to be configured on both terminating switches.

Q4: Use LACP whenever possible; static trunking should only be used when LACP isn't possible.

Related Solutions

Cisco – Etherchannel connections between Cisco and Nortel switches

Look at this link and scroll about half way down.

http://forums.networkinfrastructure.info/nortel-ethernet-switching/ers-8300-and-lacp-with-hp-blade-servers/

UPDATE: Fixed - Here's how you get LACP to work with the 8300.

The configuration is simple, for a base line.

Configure your ports and vlans as you would normally (for multiple vlans enable tagging on the port level)

config ethernet 1/1-1/2,2/1-2/2 perform-tagging enable
config ethernet 1/1-1/2,2/1-2/2 lacp key 10
config ethernet 1/1-1/2,2/1-2/2 lacp aggregate true
config ehternet 1/1-1/2,2/1-2/2 lacp enable

config vlan 2 create byport 1
config vlan 2 ports add 1/1-1/2,2/1-2/2 member portmember

Configure your mlt group

config mlt 5 create
config mlt 5 lacp key 10
config mlt 5 lacp enable

Cisco – Does 2504 WLC support LAG

Yes, the 2504 supports LAG in v7.4. Your first guide refers to v7.0.116.0 and the second guide written in 5/2013 implies v7.4. Enabling LAG requires a reboot of the WLC and has limitations similar to the 5500.

When LAG is enabled on a WLC, the WLC forwards data frames on the same port on which they were received. The WLC relies on the neighbor switch to load-balance traffic across the EtherChannel. The WLC does not perform any EtherChannel load-balancing on its own.

Limitations/Restrictions, same as 5500 but note 5508 doesn't have ap-manager inf's:

LAG requires the EtherChannel to be configured for 'mode on' on both the controller and the Catalyst switch.

The load-balancing method configured on the Catalyst switch must be a load-balancing method that terminates all IP datagram fragments on a single controller port. Not following this recommendation may result in problems with access point association.

The recommended load-balancing method for Catalyst switches is src-dst-ip (enter the port-channel load-balance src-dst-ip command).

With LAG, all of the controller ports need to connect to the same neighbor switch. If the neighbor switch goes down, the controller loses connectivity. With multiple AP-manager interfaces, you can connect your ports to different neighbor devices. If one of the neighbor switches goes down, the controller still has connectivity. However, using multiple AP-manager interfaces presents certain challenges when port redundancy is a concern.

Port mirroring is not supported when link aggregation (LAG) is enabled on the controller.

Best Answer

Related Solutions

Cisco – Etherchannel connections between Cisco and Nortel switches

Cisco – Does 2504 WLC support LAG

Related Topic