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Configuring Metro Features
December 2005
© Foundry Networks, Inc.
8 - 23
In Figure 8.11, the track port is up. SInce the port is up, the track priority does not affect the VSRP priority
calculation. If the track port goes down, the track priority does affect VSRP priority calculation, as shown in Figure
8.12.
Figure 8.12
Track port priority subtracted during priority calculation
MAC Address Failover on VSRP-Aware Devices
VSRP-aware devices maintain a record of each VRID and its VLAN. When the device has received a Hello
message for a VRID in a given VLAN, the device creates a record for that VRID and VLAN and includes the port
number in the record. Each subsequent time the device receives a Hello message for the same VRID and VLAN,
the device checks the port number.
•
If the port number is the same as the port that previously received a Hello message, the VSRP-aware device
assumes that the message came from the same VSRP Master that sent the previous message.
•
If the port number does not match, the VSRP-aware device assumes that a VSRP failover has occurred to a
new Master, and moves the MAC addresses learned on the previous port to the new port.
The VRID records age out if unused. This can occur if the VSRP-aware device becomes disconnected from the
Master. The VSRP-aware device will wait for a Hello message for the period of time equal to the following:
VRID Age = Dead In Hold-down In (3 x Hello Interval)
The values for these timers are determined by the VSRP device sending the Hello messages. If the Master uses
the default timer values, the age time for VRID records on the VSRP-aware devices is as follows:
3 + 2 + (3 x 1) = 8 seconds
In this case, if the VSRP-aware device does not receive a new Hello message for a VRID in a given VLAN, on any
port, the device assumes the connection to the Master is unavailable and removes the VRID record.
Timer Scale
The VSRP Hello interval, Dead interval, Backup Hello interval, and Hold-down interval timers are individually
configurable. You also can easily change all the timers at the same time while preserving the ratios among their
values. To do so, change the timer scale. The
timer scale
is a value used by the software to calculate the timers.
The software divides a timer’s value by the timer scale value. By default, the scale is 1. This means the VSRP
timer values are the same as the values in the configuration.
VSRP
Aware
VSRP
Backup
optional link
VSRP
Aware
Configured priority = 100
Actual priority = 100 * (3/3) = 100
VSRP
Master
Track link
is down
VSRP
Aware
Configured priority = 100
Track priority 20
Actual priority = (100 - 20) * (3/3) = 80
X
F
F
F
B
B
B
Summary of Contents for FastIron Edge Switch X424
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