Trunk configuration methods

The switch automatically negotiates trunked links between LACP-configured ports on separate devices, and offers one dynamic trunk option: LACP. To configure the switch to initiate a dynamic LACP trunk with another device, use the interface command in the CLI to set the default LACP option to active on the ports you want to use for the trunk. For example, the following command sets ports C1 to C4 to LACP active:

The preceding example works if the ports are not already operating in a trunk. To change the LACP option on ports already operating as a trunk, you must first remove them from the trunk. For example, if ports C1 to C4 are LACP-active and operating in a trunk with another device, you would do the following to configure them to LACP-passive:

Removes the ports from the trunk:

Dynamic LACP trunking enables you to configure standby links for a trunk by including more than eight ports in a dynamic LACP trunk configuration. When eight ports (trunk links) are up, the remaining link(s) will be held in standby status. If a trunked link that is “Up” fails, it will be replaced by a standby link, which maintains your intended bandwidth for the trunk. (Refer to also the “Standby” entry under “Port Status” in "Table 4-5. LACP Port Status Data" on page 4-22.) In the next example, ports A1 through A9 have been configured for the same LACP trunk. Notice that one of the links shows Standby status, while the remaining eight links are “Up”.

HP Switch> show lacp
                              LACP
       LACP      Trunk    Port                LACP    Admin    Oper
Port   Enabled   Group    Status   Partner   Status   Key      Key
----   -------   -----    ------   -------   ------   ----    -----
Al     Active     Dyn1     Up        Yes     Success   100      100
A2     Active     Dyn1     Up        Yes     Success   100      100
A3     Active     Dyn1     Up        Yes     Success   100      100
A4     Active     Dyn1     Up        Yes     Success   100      100
A5     Active     Dyn1     Up        Yes     Success   100      100
A6     Active     Dyn1     Up        Yes     Success   100      100
A7     Active     Dyn1     Up        Yes     Success   100      100
A8     Active     Dyn1     Up        Yes     Success   100      100
A9     Active     Dyn1    Standby    Yes     Success   100      100

HP Switch# show lacp local
LACP Local Information.
System ID: 001871-b98500
               LACP                Tx      Rx Timer
Port   Trunk   Mode   Aggregated   Timer   Expired
----- ------- ------- ----------- ------ ---------
A2       A2    Active    Yes       Fast    No
A3       A3    Active    Yes       Fast    No

Use the show lacp peer command to display information about LACP peers. The System ID represents the MAC address of a partner switch. It will be zero if a partner is not found.

(HP_Switch_name#) show lacp peer
LACP Peer Information.
System ID: 001871-b98500
Local  Local                         Port       Oper    LACP    Tx
Port   Trunk   System ID      Port   Priority   Key     Mode    Timer
------ ------ --------------  ----- --------- ------- -------- -----
A2     A2      123456-654321   2       0       100    Passive   Fast
A3     A3      234567-456789   3       0       100    Passive   Fast

Use the show lacp counters command to display statistical information about LACP ports.

Note on the Marker Protocol. Data traffic can be dynamically redistributed in port channels. This may occur when a link is added or removed, or there is a change in load-balancing. Traffic that is redistributed in the middle of a traffic flow could potentially cause mis-ordered data packets.

LACP uses the marker protocol to prevent data packets from being duplicated or reordered due to redistribution. Marker PDUs are sent on each port-channel link. The remote system responds to the marker PDU by sending a marker responder when it has received all the frames received on this link prior to the marker PDU. When the marker responders are received by the local system on all member links of the port channel, the local system can redistribute the packets in the traffic flow correctly.

For the switches covered in this guide, the marker BPDUs are not initiated, only forwarded when received, resulting in the Marker fields in the output usually displaying zeros.

(HP_Switch_name#) show lacp counters
LACP Port Counters.
               LACP      LACP      Marker    Marker    Marker     Marker
Port   Trunk   PDUs Tx   PDUs Rx   Req. Tx   Req. Rx   Resp. Tx   Resp. Rx   Error
----   ------  -------   -------   -------   -------   --------   --------   -----
A2       A2    1234      1234       0          0         0         0           0
A3       A3    1234      1234       0          0         0         0           0

The lacp key option provides the ability to control dynamic trunk configuration. Ports with the same key will be aggregated as a single trunk.

There are two types of keys associated with each port, the Admin key and the Operational key. The Operational key is the key currently in use. The Admin key is used internally to modify the value of the Operational key. The Admin and Operational key are usually the same, but using static LACP can alter the Operational key during runtime, in which case the keys would differ.

The lacp key command configures both the Admin and Operational keys when using dynamic LACP trunks. It only configures the Admin key if the trunk is a static LACP trunk. It is executed in the interface context.

The switch uses the links you configure with the Port/Trunk Settings screen in the menu interface or the trunk command in the CLI to create a static port trunk. The switch offers two types of static trunks: LACP and Trunk.

Trunk configuration protocols describes the trunking options for LACP and Trunk protocols.

Operating port trunks

Media:	For proper trunk operation, all ports on both ends of a trunk group must have the same media type and mode (speed and duplex.) (For the switches, HP Switch recommends leaving the port Mode setting at Auto or, in networks using Cat 3 cabling, Auto-10.)
Port Configuration	The default port configuration is Auto, which enables a port to sense speed and negotiate duplex with an auto-enabled port on another device. HP Switch recommends that you use the Auto setting for all ports you plan to use for trunking. Otherwise, you must manually ensure that the mode setting for each port in a trunk is compatible with the other ports in the trunk.

Recommended port mode setting for LACP

(HP_Switch_name#) show interfaces config

 Port Settings

  Port  Type      | Enabled Mode         Flow Ctrl MDI
  ----- --------- + ------- ------------ --------- ----
  1     10/100TX  | Yes     Auto         Enable    Auto
  2     10/100TX  | Yes     Auto         Enable    MDI

All of the following operate on a per-port basis, regardless of trunk membership:

• Enable/Disable

• Flow control (Flow Ctrl)

LACP is a full-duplex protocol.

Trunk configuration:	All ports in the same trunk group must be the same trunk type (LACP or trunk.) All LACP ports in the same trunk group must be either all static LACP or all dynamic LACP. A trunk appears as a single port labeledDyn1(for an LACP dynamic trunk) or Trk1 (for a static trunk of type LACP, Trunk) on various menu and CLI screens. For spanning-tree or VLAN operation, configuration for all ports in a trunk is done at the trunk level. (You cannot separately configure individual ports within a trunk for spanning-tree or VLAN operation.)
Traffic distribution:	All of the switch trunk protocols use the SA/DA (source address/destination address) method of distributing traffic across the trunked links.
Spanning Tree:	802.1D (STP) and 802.1w (RSTP) Spanning Tree operate as a global setting on the switch (with one instance of Spanning Tree per switch.) 802.1s (MSTP) Spanning Tree operates on a per-instance basis (with multiple instances allowed per switch.) For each Spanning Tree instance, you can adjust Spanning Tree parameters on a per-port basis. A static trunk of any type appears in the Spanning Tree configuration display, and you can configure Spanning Tree parameters for a static trunk in the same way that you would configure Spanning Tree parameters on a non-trunked port. (Note that the switch lists the trunk by name—such as Trk1—and does not list the individual ports in the trunk.) For example, if ports C1 and C2 are configured as a static trunk named Trk1, they are listed in the Spanning Tree display as Trk1 and do not appear as individual ports in the Spanning Tree displays. When Spanning Tree forwards on a trunk, all ports in the trunk will be forwarding. Conversely, when Spanning Tree blocks a trunk, all ports in the trunk are blocked. NOTE: A dynamic LACP trunk operates only with the default Spanning Tree settings. Also, this type of trunk appears in the CLI show spanning-tree display, but not in the Spanning Tree Operation display of the Menu interface. If you remove a port from a static trunk, the port retains the same Spanning Tree settings that were configured for the trunk.

Example of a port trunk in a Spanning Tree listing

IP multicast protocol (IGMP):	A static trunk of any type appears in the IGMP configuration display, and you can configure IGMP for a static trunk in the same way that you would configure IGMP on a non-trunked port. (Note that the switch lists the trunk by name—such as Trk1—and does not list the individual ports in the trunk.) Also, creating a new trunk automatically places the trunk in IGMP Auto status if IGMP is enabled for the default VLAN. A dynamic LACP trunk operates only with the default IGMP settings and does not appear in the IGMP configuration display or show ip igmp listing.
VLANs:	Creating a new trunk automatically places the trunk in the DEFAULT_VLAN, regardless of whether the ports in the trunk were in another VLAN. Similarly, removing a port from a trunk group automatically places the port in the default VLAN. You can configure a static trunk in the same way that you configure a port for membership in any VLAN. NOTE: For a dynamic LACP trunk to operate in a VLAN other than the default VLAN (DEFAULT_VLAN), GVRP must be enabled.
Port security	Trunk groups (and their individual ports) cannot be configured for port security, and the switch excludes trunked ports from the show port-security listing. If you configure non-default port security settings for a port, then subsequently try to place the port in a trunk, you see the following message and the command is not executed: <PORT-LIST> Command cannot operate over a logical port.
Monitor port	NOTE: A trunk cannot be a monitor port. A monitor port can monitor a static trunk but cannot monitor a dynamic LACP trunk.

	IMPORTANT: Configure port trunking before you connect the trunked links between switches. Otherwise, a broadcast storm could occur. (If you need to connect the ports before configuring them for trunking, you can temporarily disable the ports until the trunk is configured.)

The table on Trunk types used in static and dynamic trunk groups describes the maximum number of trunk groups you can configure on the switch. An individual trunk can have up to eight links, with additional standby links if you are using LACP. You can configure trunk group types as follows:

In the default port configuration, all ports on the switch are set to disabled. To enable the switch to automatically form a trunk group that is dynamic on both ends of the link, the ports on one end of a set of links must be LACP Active. The ports on the other end can be either LACP Active or LACP Passive. The active command enables the switch to automatically establish a (dynamic) LACP trunk group when the device on the other end of the link is configured for LACP Passive.

Example

Criteria for automatically forming a dynamic LACP trunk

Dynamic LACP trunking enables you to configure standby links for a trunk by including more than eight ports in a dynamic LACP trunk configuration. When eight ports (trunk links) are up, the remaining links are held in standby status. If a trunked link that is "Up" fails, it is replaced by a standby link, which maintains your intended bandwidth for the trunk. (See also the "Standby" entry under "Port Status" in LACP port status data.) In the next example, ports A1 through A9 have been configured for the same LACP trunk. Notice that one of the links shows Standby port status, while the remaining eight links show Up port status.

Example

HP Switch> show lacp

                              LACP

      LACP      Trunk     Port               LACP     Admin  Oper
Port  Enabled   Group     Status   Partner  Status    Key    Key
----  -------   -------   -------  -------  -------   ------ ------ 
Al    Active    Dyn1      Up       Yes      Success   100    100
A2    Active    Dyn1      Up       Yes      Success   100    100
A3    Active    Dyn1      Up       Yes      Success   100    100
A4    Active    Dyn1      Up       Yes      Success   100    100
A5    Active    Dyn1      Up       Yes      Success   100    100
A6    Active    Dyn1      Up       Yes      Success   100    100
A7    Active    Dyn1      Up       Yes      Success   100    100
A8    Active    Dyn1      Up       Yes      Success   100    100
A9    Active    Dyn1      Standby  Yes      Success   100    100

Use the show lacp peer command to display information about LACP peers. The System ID represents the MAC address of a partner switch. It will be zero if a partner is not found.

(HP_Switch_name#) show lacp peer

LACP Peer Information. 

System ID: 001871-b98500

  Local  Local                       Port      Oper    LACP     Tx
  Port   Trunk  System ID      Port  Priority  Key     Mode     Timer
  ------ ------ -------------- ----- --------- ------- -------- ----- 
  A2     A2     123456-654321  2     0         100     Passive  Fast
  A3     A3     234567-456789  3     0         100     Passive  Fast

Use the show lacp counters command to display statistical information about LACP ports.

	NOTE: Data traffic can be dynamically redistributed in port channels. This may occur when a link is added or removed, or there is a change in load-balancing. Traffic that is redistributed in the middle of a traffic flow could potentially cause mis-ordered data packets. LACP uses the marker protocol to prevent data packets from being duplicated or reordered due to redistribution. Marker PDUs are sent on each port-channel link. The remote system responds to the marker PDU by sending a marker responder when it has received all the frames received on this link prior to the marker PDU. When the marker responders are received by the local system on all member links of the port channel, the local system can redistribute the packets in the traffic flow correctly.

For the switches covered in this guide, the marker BPDUs are not initiated, only forwarded when received, resulting in the Marker fields in the output usually displaying zeros.

(HP_Switch_name#) show lacp counters

LACP Port Counters.


  LACP        LACP      Marker    Marker   Marker   Marker
  Port Trunk  PDUs Tx   PDUs Rx   Req. Tx  Req. Rx  Resp. Tx Resp. Rx Error
  ---- ------ --------- --------- -------- -------- -------- -------- --------
  A2   A2     1234      1234      0        0        0        0        0
  A3   A3     1234      1234      0        0        0        0        0