Jeremy's profileMind SharePhotosBlogListsMore  |  Tools Help |
|
November 19 Linux EtherChannel - Double Your Pleasure Double Your FunAs always I'm long overdue for an update. I've been busy with other more important things, but I figured since I had to document this for others within my group, here would be the best place since it might benefit others as well.
For today's exercise we'll be creating an EtherChannel between a Red Hat Enterprise 5 server, and a Cisco Catalyst 3750 Switch. This is actually far simpler then it sounds, and can be completed in about ten minutes.
We'll begin with configuring the IEEE 802.3ad Dynamic link aggregation (AKA EtherChannel) on the Red Hat Enterprise Linux server. Begin by logging in via SSH, Telnet or directly on the console itself. I do recommend having access to the console directly, so should anything go wrong and you lose network connectivity you'll be able to easily change things back.
Once logged into the server, switch user to "root" if you're not already logged in as root. Change directory to "/etc" and modify the "modprobe.conf" file using your favorite text editor such as "vi". I personally like using "nano". Add the lines in bold from the example "modprobe.conf" below to your file. Then save your changes and return to the bash prompt.
Sample /etc/modprobe.conf
Next we need to create a network script for the "bond0" interface that we defined above in the "modprobe.conf" file. This will be used to configure the network properties for the virtual adapter. Once again, use your favorite text editor to create a new file called "ifcfg-bond0" in the "/etc/sysconfig/network-scripts" directory. In this file you will define the device name used above"bond0", IP address, gateway, network mask etc for the virtual adapter. Below is an example.
Sample /etc/sysconfig/network-scripts/ifcfg-bond0
When you're done configuring the properties of the virtual adapter, save your changes and exit the editor.
The next step is to modify the network script for each adapter that will be added to the EtherChannel. The adapters that we'll be using in this server are eth0 and eth1. Please note your interfaces may be different, so check before continuing.
Start by modifying "ifcfg-<int>" using your text editor, where <int> is the interface name. In this case my file name is "ifcfg-eth0". Add the proper references to the virtual adapter created above "bond0" and remove any IP information such as IP address, gateway, netmask etc since that information will be handled by the virtual adapter. Below is an example of the "ifcfg-eth0" file. Note the bold items are required for the EtherChannel to function properly.
Sample /etc/sysconfig/network-scripts/ifcfg-eth0
Repeat the steps above for each additional interface you add to the Etherchannel.
Sample /etc/sysconfig/network-scripts/ifcfg-eth1
Now that each physical adapter has been associated to the virtual adapter, it's now time to create the EtherChannel on the Cisco switch that this server is connected to. In this example I'll be using two Cisco Catalyst 3750G switches in a stack. In addition to the added benefit of increased bandwidth that the EtherChannel provides, having multiple switches will add switch level redundancy to the EtherChannel.
Begin by logging into the switch, entering configuration mode, and creating the EtherChannel interface. The EtherChannel interface, also known as a "Port-channel", is a virtual interface. You can use any number from 1-48 that isn't already assigned to another EtherChannel. In this example I'll be using "28". Configure all the properties such as VLAN, switchport mode etc. that you would normally define on the physical interfaces. Please note that the properties defined in the EtherChannel will override any interface configuration you have defined on the physical interfaces this Etherchannel is assigned to.
Next we'll need to configure the physical interfaces by associating them to the EtherChannel we created above. I like to mirror the configuration of the EtherChannel on the physical interfaces, so in the event the EtherChannel on the far end of the link becomes misconfigured the server will still be accessible. The line in bold is the only required change that needs to be made on the physical interfaces.
Repeat the process for each additional interface in the EtherChannel.
It's now time to restart the network service on the Linux server. Optionally you can reboot the Linux server if that's easier.
Check the status of the EtherChannel on the Linux server. If the EtherChannel is operating properly you should see "Bonding Mode: IEEE 802.3ad Dynamic link aggregation" when you concatenate "/proc/net/bonding/bond0"
To check the status of the etherchannel on the Cisco switch, use the "show ether-channel" command.
At this point you should have a fully functional EtherChannel. If you have any questions feel free to post comments, or contact me directly.  |
|
|
