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SC Network Interfaces

There are several network interfaces used on an SC to communicate with the platform, domains, and the other SC. These are defined in a similar fashion to regular network connections through /etc/hostname.* entries.


Note – For the purposes of this discussion the main SC is sc0 while the spare SC is always sc1. If no hardware failures are present and the SCs are booted at the same time sc0 will always become the main SC. As the network configuration is slightly different between sc0 and sc1, they are referred to as main and spare respectively.

Main SC Network Interfaces

A typical main SC, or sc0, will have the following two files in /etc with contents similar to the following:

# more /etc/hostname.scman0 netmask + private up
# more /etc/hostname.scman1 netmask + private up

In addition, a typical sc0 SC will have the corresponding entries in /etc/netmasks:


Non-routed, or RFC 1918, IP addresses have been used in all SC examples. It is recommended that these types of IP addresses be used when deploying Sun Fire 15K SCs. The SMS software defines internal SC networks connections to be private, and not advertised.

The /etc/hostname.scman0 entry sets up the I1 or Domain to SC Management Network (MAN). The IP address used in this example,, is a floating IP address controlled by the SMS software to always be available only on the main SC.

From a security perspective, the network between the domains and the SC, in addition to any network connection between the domains, is of concern. The I1 network addresses these concerns by only permitting SC-to-domain and domain-to-SC communication. This is implemented through a point-to-point physical network connection between the SC and each of the 18 domains supported by a Sun Fire 15K system. On the SC, these 18 separate networks are consolidated into one meta-interface to simplify administration and management. The MAN driver software performs this consolidation and also enforces domain separation and failovers to redundant communication paths.

Direct communication between domains, over the I1 network, is not permitted by the hardware implementation of the I1 network. This network is implemented through 18 separate point-to-point networks between the SCs and each domain. Each of these connections terminates at separate I/O boards on each domain and SC.

By implementing the network in this manner, each SC to domain network connection is physically isolated from the other connections. The only restriction is that the MAC addresses used by each domain are sequentially incremented from domain 1 to 18.

The /etc/hostname.scman1 entry is used to configure the I2 or SC-to-SC Management Network (MAN). This network connection, on which both SC's have an IP address, is used for the heartbeat connections between the two SCs.

Both of these network connections are implemented through the Sun Fire 15K internal MAN. No external wiring is utilized.


Do not use the MAN networks for any reason. These are Sun Fire 15K networks and not for general purpose use. Any use may interfere with the proper operation of the SMS monitoring agents.

Putting them all together, the network configuration appears as follows on the main SC which is sc0 in this article:

# ifconfig -a
    mtu 8232 index 1 inet netmask ff000000 

    mtu 1500 index 2 inet netmask fffff800 
    broadcast ether 8:0:20:a8:db:2e 

    mtu 1500 index 3 inet netmask ffffffe0 
    broadcast ether 8:0:20:a8:db:2e 

    mtu 1500 index 4 inet netmask fffffffc 
    broadcast ether 8:0:20:a8:db:2e

While the scman0 and scman1 networks are Internet Protocol (IP) based network segments they should not be used as a general purpose network segment. For example, even though an SC and a domain will be on scman0, network administrators should not use scman0 for transferring files nor other administrative tasks. Refer to the scman(7D) and dman(7D) man pages for more details.


Do not use the MAN networks for any reason. These are Sun Fire 15K networks and not for general purpose use. Any use may interfere with the proper operation of the SMS monitoring agents.

Spare SC Network Interfaces

The spare SC has the same physical network interfaces as the main SC but with a slightly different configuration as it is in spare mode. The status of the SC can be verified with the following command:

# showfailover -r

The scman0 network interface is plumbed by the Solaris OE through the /etc/hostname.scman0 file on the spare SC in the same manner, and with the same information, as on the main SC. The difference between the main and spare SCs is that the interface will be inactive on the spare. The spare SCs scman0 port on the I/O hubs is disabled and mand will not provide path information to scman0 on the spare.

The scman1 interface, which is used for SC to SC communications, will be plumbed and the spare SC has the following configuration information for this interface:

# more /etc/hostname.scman1 netmask + private up

In addition, the spare SC has the following corresponding /etc/netmask information:

Putting them all together, the network configuration appears as follows on the spare SC which is sc1 in this example:

# ifconfig -a
    mtu 8232 index 1 inet netmask ff000000 

    mtu 1500 index 2  inet netmask ffffff00 

      mtu 1500 index 3 inet netmask ffffffe0 

      mtu 1500 index 4  inet netmask fffffffc 

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