Dell 3-DNS, Administrator'S Manual

Page: 74 / 165

Chapter 4
4 - 12
Find the MAC address on both the active and standby units, and pick one
that is similar but unique. A safe technique for selecting the shared MAC
address follows.
Suppose you want to set up mac_masq on the external interfaces. Using the
b interface show command on the active and standby units, you note that
their MAC addresses are:
Active: 3.1 = 0:0:0:ac:4c:a2
Standby: 3.1 = 0:0:0:ad:4d:f3
In order to avoid packet collisions, you now must choose a unique MAC
address. The safest way to do this is to select one of the addresses, and
convert the MAC address to a locally administered address using
0x40 for
the first byte. (The 0x40 byte indicates the logical operator OR .)
In this example, either 40:0:0:ac:4c:a2 or 40:0:0:ad:4d:f3 would be a
suitable shared MAC address to use on both 3-DNS units in the redundant
system.
The shared MAC address is used only when the 3-DNS Controller is in
active mode. When the unit is in standby mode, the original MAC address of
the network card is used.
If you do not configure mac_masq on startup, or when transitioning from
standby mode to active mode, the 3-DNS Controller sends gratuitous ARP
requests to notify the default router and other machines on the local Ethernet
segment that its MAC address has changed. See RFC 826 for more details
on ARP.
Note
The MAC masquerade information is stored in the bigip_base.conf file.
Configuring a self IP address
A self IP address is an IP address mapping to one or more VLANs and their
associated interfaces on a 3-DNS Controller. You assign a self IP address to
each interface on the unit as part of the initial configuration, and you also
assign a floating (shared) alias for units in a redundant system. You can
create additional self IP addresses for health checking, gateway failsafe,
routing, or other purposes. You create additional self IP addresses using
either the Configuration utility or using the
self command in the bigpipe
utility. (See the 3-DNS Reference Guide , Appendix B, bigpipe Command
Reference , for more information on the self command.)
To add a self IP address to a VLAN using the Configuration
utility
1. In the navigation pane, click Network .
The VLANs screen opens.
2. Click the Self IP Addresses tab.