Configuring Metro Features
December 2005 © Foundry Networks, Inc. 8 - 31
the highest priority, the Backup with the highest IP address becomes the Master for the VRID.
• The track priority is used with the track port feature. See “VSRP Priority Calculation” on page 8-20 and
“Changing the Default Track Priority” on page 8-33.
To change the backup priority, enter a command such as the following at the configuration level for the VRID:
FastIron SuperX Router(config-vlan-200-vrid-1)# backup priority 75
Syntax: [no] backup [priority <value>] [track-priority <value>]
The priority <value> parameter specifies the VRRP priority for this interface and VRID. You can specify a value
from 3 – 254. The default is 100.
For a description of the track-priority <value> parameter, see “Changing the Default Track Priority” on page 8-33.
Saving the Timer Values Received from the Master
The Hello messages sent by a VRID’s master contain the VRID values for the following VSRP timers:
• Hello interval
• Dead interval
• Backup Hello interval
• Hold-down interval
By default, each Backup saves the configured timer values to its startup-config file when you save the device’s
configuration.
You can configure a Backup to instead save the current timer values received from the Master when you save the
configuration. Saving the current timer values instead of the configured ones helps ensure consistent timer usage
for all the VRID’s devices.
NOTE: The Backups always use the value of the timer scale received from the Master, regardless of whether the
timer values that are saved in the configuration are the values configured on the Backup or the values received
from the Master.
To configure a Backup to save the VSRP timer values received from the Master instead of the timer values
configured on the Backup, enter the following command:
FastIron SuperX Router(config-vlan-200-vrid-1)# save-current-values
Syntax: [no] save-current-values
Changing the Time-To-Live (TTL)
A VSRP Hello packet’s TTL specifies how many hops the packet can traverse before being dropped. A hop can be
a Layer 3 Switch or a Layer 2 Switch. You can specify from 1 – 255. The default TTL is 2. When a VSRP device
(Master or Backup) sends a VSRP HEllo packet, the device subtracts one from the TTL. Thus, if the TTL is 2, the
device that originates the Hello packet sends it out with a TTL of 1. Each subsequent device that receives the
packet also subtracts one from the packet’s TTL. When the packet has a TTL of 1, the receiving device
subtracts 1 and then drops the packet because the TTL is zero.
NOTE: An MRP ring is considered to be a single hop, regardless of the number of nodes in the ring.
To change the TTL for a VRID, enter a command such as the following at the configuration level for the VRID:
FastIron SuperX Router(config-vlan-200-vrid-1)# initial-ttl 5
Syntax: [no] initial-ttl <num>
The <num> parameter specifies the TTL and can be from 1 – 255. The default TTL is 2.
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