Specifications

Chapter 2. IBM System Networking Switch 10Gb Ethernet switch features 83
Virtual router MAC address
The VRID is used to build the virtual router MAC Address. The five highest-order octets of the
virtual router MAC Address are the standard MAC prefix (00-00-5E-00-01) defined in RFC
2338. The VRID is used to form the lowest-order octet.
Owners and renters
Only one of the VRRP routers in a virtual router may be configured as the IPv4 address
owner. This router has the virtual router’s IPv4 address as its real interface address. This
router responds to packets addressed to the virtual router’s IPv4 address for ICMP pings,
TCP connections, and so on.
There is no requirement for any VRRP router to be the IPv4 address owner. Most VRRP
installations choose not to implement an IPv4 address owner. For the purposes of this
chapter, VRRP routers that are not the IPv4 address owner are called
renters.
Master and backup virtual router
Within each virtual router, one VRRP router is selected to be the virtual router master. For an
explanation of the selection process, see “Selecting the master VRRP router” on page 83.
The virtual router master forwards packets sent to the virtual router. It also responds to
Address Resolution Protocol (ARP) requests sent to the virtual router's IPv4 address. Finally,
the virtual router master sends out periodic advertisements to inform other VRRP routers that
it is alive and what its priority is.
Within a virtual router, the VRRP routers not selected to be the master are known as
virtual
router backups
. Should the virtual router master fail, one of the virtual router backups
becomes the master, and assumes its responsibilities.
Virtual Interface Router
At Layer 3, a VIR allows two VRRP routers to share an IP interface across the routers. VIRs
provide a single DIP address for upstream routers to reach various destination networks, and
provide a virtual default gateway.
Virtual Router Redundancy Protocol operation
Only the virtual router master responds to ARP requests. Therefore, the upstream routers
only forward packets destined to the master. The master also responds to ICMP ping
requests. The backup does not forward any traffic, nor does it respond to ARP requests.
If the master is not available, the backup becomes the master and takes over responsibility
for packet forwarding and responding to ARP requests.
Selecting the master VRRP router
Each VRRP router is configured with a priority 1 - 254. A bidding process determines which
VRRP router is or becomes the master, that is, the VRRP router with the highest priority.
Virtual router master: If the virtual IPv4 address owner is available, it always becomes
the virtual router master.
VIR considerations: Every VIR must be assigned to an IP interface, and every IP
interface must be assigned to a VLAN. If no port in a VLAN has a link up, the IP interface of
that VLAN is down, and if the IP interface of a VIR is down, that VIR goes into INIT state.