Citrix states in their article: CTX434260

CTX434260 - NIC Teaming - Compaq NICs with Cisco Switches (EtherChannel)

This document was published at: http://support.citrix.com/kb/entry.jspa?externalID=CTX434260

Document ID: CTX434260, Created on: Oct 29, 2001, Updated: Apr 23, 2003

Products: Citrix MetaFrame XP 1.0 for Microsoft Windows 2000, Citrix MetaFrame 1.8 for Microsoft Windows 2000

How to configure teaming NICs with Cisco Switches

There are several NIC teaming technologies available today from switch vendors. Cisco uses the term “EtherChannel.” Various switch vendors use various terms, and these may or may not provide the same exact functionality.

Cisco EtherChannel is a failover and load-distribution technology wherein the same MAC address or IP address is bound to two, four, or eight FastEthernet or GigabitEthernet NICs, providing parallel links. This translates into high bandwidth, load sharing, and redundancy. Citrix MetaFrame supports this technology, and it is considered a best practice where feasible.

It is unlikely that more than two EtherChannel links will be required per MetaFrame server. The primary purpose for using EtherChannel is to ensure redundancy and uninterrupted service in the event of a NIC or switch port failure; network bandwidth and load requirements in a well-running environment are generally not higher than a single full-duplex FastEthernet NIC can support. In addition to the basic redundancy provided by the virtual interface created during EtherChannel teaming, EtherChannel does improve on the load capacity of the NIC by providing double (in the case of two NICs) or quadruple (in the case of four NICs) the throughput of one NIC.

EtherChannel is sometimes configured improperly, causing the optimization goals expected to instead create a multitude of network issues. All switch ports must belong to the same subnet and/or VLAN. The same speed and duplex settings must be available and manually configured on both the switch port and the NIC. Further, Cisco IOS version 12 or higher should be used.

When configuring the switch to support EtherChannel, the port group can be created automatically using Port Aggregation Protocol or by manual configuration. The latter is recommended to create a port group for the switch ports that will correspond to the teamed NICs. This exact command for creating a port group varies according to the switch model. For example, the network administrator would configure EtherChannel using the following command on each of the switch ports to be aggregated:

2900B(config-if)#port group [#] distribution [source|destination]

If source is chosen as the distribution method, then all blocks of incoming packets from the same source will traverse through the same port. This is the default and is recommended. If destination is chosen as the distribution method, then all incoming packets are forwarded based only on the destination.

Contiguous ports must be used for EtherChannel connections on some stackable Cisco switches. Thus, in a Cisco environment where this is required, on a 12-port switch, bundle the connections into ports 1-4, 5-8, or 9-12; on a 24-port switch, it is best to bundle the connections into ports 1-8, 9-16, or 17-24. On the larger non-stackable Cisco switches, such as the 6500 series, EtherChannel ports should be spread across blades to provide higher redundancy.

Use of EtherChannel technology requires support from the server hardware vendor, NIC vendor, and layer-2 switch vendor. As of June 2002, Cisco supports NICs from the following vendors: Adaptec, Auspex, Compaq, Hewlett-Packard, Intel, Phobos, Sun Microsystems, and ZNYX.

When using the Compaq drivers, the most up-to-date teaming driver as of December 2002 is CP002710.exe, which installs Compaq driver version7.11.711.1. Use Add/Remove Programs to load the teaming driver; failure to do so may cause the NIC teaming to appear to be configured but not actually do so. After the teaming driver is loaded, each NIC should be manually set to the maximum speed and full duplex. Then, the NICs should be selected and Team should be chosen. Lastly, the Teaming Controls should be set to Load Balancing and Switch-Assisted Load Balancing. Load balancing can be achieved via MAC address or IP address. Using the MAC address for load balancing is advantageous since it is performed at layer 2, which is the same OSI layer where the switch resides. Teaming by IP address is not recommended since IP address can change and are dependent upon server configuration and MAC address. After configuring NIC teaming, reboot if necessary and reset the TCP/IP address of the single newly teamed virtual NIC; failure to do so will likely result in the NIC defaulting to a 169.254.x.x address, which will not communicate properly with the server farm.

To avoid issues with Spanning Tree, either the switch ports connected to the MetaFrame server NICs could be disabled from participating in Spanning Tree or PortFast should be used. The latter is recommended. PortFast enables switch ports that will not participate in Spanning Tree to connect to the network in less than one second by entering the “forwarding” state. Thus, the 50-second Spanning Tree process is minimized.

To configure a Cisco 2900 switch for PortFast, the following should be configured for each switch port that connects to a MetaFrame server NIC that is using EtherChannel teaming.

2900B(config-if)#spanning-tree portfast

It is very important that servers be updated with the latest NIC drivers and that the NIC settings be rechecked after updating NIC drivers. New NIC drivers may override previously configured settings. Of course, specific instructions from the particular vendor should be followed explicitly.