Using Enterprise OS Software

Configuring LAN Address Administration

This chapter describes how to use LAN Address Administration (LAA) to assign a media access control (MAC) address to a physical path or to the main processor module interface, overriding the MAC address burned in the PROM on the physical interface.

Assigning MAC addresses to a path or main processor interface is supported for token ring, Ethernet, and FDDI ports only.

By assigning a MAC address to a path, you can use the same MAC address for multiple paths for load splitting purposes in Systems Network Architecture (SNA) environments. By assigning a MAC address to a path that is different from the MAC address burned in the physical interface PROM, you can hotswap modules on a port and still maintain the same MAC address.

CAUTION: Using LAA on paths being used to route DECnet network traffic can cause problems in DECnet environments. For more information, see "Using LAA with DECnet" later in this chapter.

LAA cannot coexist with the IP VRRP fature on the same bridge/router.

Assigning a MAC Address to a Physical Path

To assign a MAC address to a physical path, follow these steps:

1 . To assign a MAC address to a physical path (a different address from the one burned on the module PROM), use:

: SETDefault !<path> -PATH MacAddress = %<MAC address> | Mac <MAC address> | Ncmac <MAC address>

: You can enter the MAC address in one of two formats: canonical or noncanonical. To enter the address in canonical format, precede the address with the prefix "Mac" or the percent symbol (%). To enter the address in noncanonical format, precede the address with the prefix Ncmac. If you precede the MAC address with Mac or Ncmac, enter a space between the prefix and the address. If you precede the MAC address with the percent symbol (%), do not enter a space between the symbol and the address.
: Bits 0 and 1 of the first byte must be set to 0 and 1 respectively. Bit 1 is the universally and locally administered bit. This limits the choice of addresses to the following set (where x can have any value).
: In canonical format:

: x2xx xxxx xxxx
: x6xx xxxx xxxx
: xAxx xxxx xxxx
: xExx xxxx xxxx

: In noncanonical format:

: 4xxx xxxx xxxx
: 5xxx xxxx xxxx
: 6xxx xxxx xxxx
: 7xxx xxxx xxxx

: For example, to assign the canonical address 020002033D76 to path 2, enter:

: SETDefault !2 -PATH MacAddress = Mac 020002033D76

: To assign the noncanonical address 400040C0BC6E to path 2, enter:

: SETDefault !2 -PATH MacAddress = NcMac 400040C0BC6E

: To assign the MAC address 020002030EF2 in canonical format for token ring, enter:

: SETDefault !2 -PATH MacAddress = %020002030EF2

: To convert a MAC address from canonical format to noncanonical format and vice-versa, use the MacAddrConvert command. For more information, see the Commands chapter in Reference for Enterprise OS Software.
CAUTION: Do not assign a multicast address for the MAC address. Also, do not assign a MAC address that is either a smart filtering MAC address or one of the bridge BPDU addresses.

2 . After you have reassigned the MAC address, re-enable the path using:

: SETDefault !<path> -PATH CONTrol = Enabled

: After you re-enable the path, the new MAC address assigned to the path will be shown when MAC addresses for any protocol are displayed. The new address remains assigned to the interface until you specifically reset the address. The new address remains assigned after you reboot the bridge/router.

3 . If the LAA address is used by Advanced Peer-to-Peer Networking (APPN), you must deactivate and then activate the node control for the new address to be effective by entering:

: SETDefault -APPN CONTrol = Deactivate
: SETDefault -APPN CONTrol = Activate

4 . Verify that the new MAC address has been assigned by entering:

: SHow !* -PATH MacAddress

: After you have assigned a MAC address to a path, you can reassign the path back to the MAC address burned on the PROM using:

: SETDefault !<path> -PATH MacAddress = Reset

: When you reset the MAC address, the address you previously assigned is deleted.

Figure 260 shows how you can use duplicate MAC addresses by reassigning an existing address. In the figure, you reassign the MAC address on path 3 to duplicate the address on path 2. The MAC address burned in the PROM of the module on path 3 still exists, but is not used for any connections. The MAC address burned in the PROM is transparent until the MAC address is reset.

You cannot set duplicate MAC addresses on the same ring in token ring environments. If you set duplicate MAC addresses on the same bridge/router, each path must be connected to different rings.

CAUTION: Setting duplicate MAC addresses is recommended only for SNA and other connection-oriented protocols. In addition, setting duplicate MAC addresses will work only in source routing LAN environments. As a result, setting duplicate MAC addresses is not recommended on transparent bridges or source route transparent bridges.

Figure 260 Setting Duplicate MAC Addresses Using LAA

Assigning a MAC Address to a Main Processor Module Interface

You can assign a MAC address to the main processor module interface on a NETBuilder II bridge/router. This can be useful in assigning a bridge/router to act as a backup network node in APPN environments.

To assign a MAC address to the main processor module interface on a NETBuilder II bridge/router, follow the procedures in "Assigning a MAC Address to a Physical Path" earlier in this chapter. However, when setting the MacAddress parameter, instead of specifying a path number, specify !0 to represent the processor module interface. For example, to assign the noncanonical address 400040C0BC6E to the interface, enter:

: SETDefault !0 -PATH MacAddress = NcMac 400040C0BC6E

After you change the MAC address of the interface, you must reboot the bridge/router.

Using Duplicate MAC Addresses for SNA Load Balancing

You can set duplicate MAC addresses to set up load balancing for SNA environments. In Figure 261, NETBuilder C and NETBuilder D are APPN network nodes in which duplicate MAC addresses are used on both so that connections to the host from the terminals at the bottom of the figure can go through either bridge/router.

In this example, MAC addresses A and B are duplicated on NETBuilder C and NETBuilder D. In this environment, the end stations at the bottom of the figure must configure the address of the host. Half of the end stations can configure MAC address A as the address to the host, and the other end stations can configure MAC address B. Two backbone rings are required because you cannot have two stations with the same MAC address on the same ring.

Using source routing, the end stations send out a discovery packet for the host address (either address A or B). The discovery packets are bridged through both bridges (NETBuilder X and NETBuilder Y) to the backbone rings. The discovery packet flows on both backbone rings. NETBuilder C and D both respond. The workstation chooses the first path to respond. When the traffic on both bridges and rings is "load balanced," if one bridge or ring goes down, the end stations can rediscover a new path to the host without reconfiguring.

Figure 261 Using LAA for SNA Load Balancing