Brocade BigIron RX Series Configuration Guide
Brocade BigIron RX Series Configuration Guide
Multi-Service IronWare v02.9.00
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Virtual Switch Redundancy Protocol (VSRP) : Overview of Virtual Switch Redundancy Protocol (VSRP)

Overview of Virtual Switch Redundancy Protocol (VSRP)
VSRP is a Brocade proprietary protocol that provides redundancy and sub-second failover in Layer 2 and Layer 3 mesh topologies. Based on the Brocade’s proprietary Virtual Router Redundancy Protocol Extended (VRRPE), VSRP provides one or more backups for the device. If the active device becomes unavailable, one of the backups takes over as the active device and continues forwarding traffic for the network.
Layer 2 and Layer 3 share the same VSRP configuration information.
Figure 75 shows a VSRP configuration.
Figure 75 VSRP mesh – redundant paths for Layer 2 and Layer 3 traffic
In this example, two devices are configured as redundant paths for VRID 1. On each device, a Virtual Router ID (VRID) is configured on a port-based VLAN. Since VSRP is primarily a Layer 2 redundancy protocol, the VRID applies to the entire VLAN. However, you can selectively remove individual ports from the VRID if needed.
Following Master election (described below), one of the Brocade devices becomes the Master for the VRID and sets the state of all the VLAN’s ports to Forwarding. The other device is a Backup and sets all the ports in its VRID VLAN to Blocking.
If a failover occurs, the Backup becomes the new Master and changes all its VRID ports to the Forwarding state.
Other Brocade devices can use the redundant paths provided by the VSRP devices. In this example, three Brocade devices use the redundant paths. A Brocade device that is not itself configured for VSRP but is connected to a Brocade device that is configured for VSRP, is VSRP aware. In this example, the three Brocade devices connected to the VSRP devices are VSRP aware. A Brocade device that is VSRP aware can failover its link to the new Master in sub-second time, by changing the MAC address associated with the redundant path.
When you configure VSRP, make sure each of the non-VSRP Brocade devices connected to the VSRP devices has a separate link to each of the VSRP devices.
When using the BigIron RX in conjunction with a FastIron Edge Switch, FastIron GS Series Switch, FastIron LS Series Switch, FastIron Edge Switch X Series Switch, or the FastIron Edge Switch X Series Switch as the VSRP-aware switches, the vsrp-aware vrid <num> tc-vlan-flush command is required to be configured on the non-BigIron RX devices. Refer to the FastIron Configuration Guide for additional information.
Layer 2 and Layer 3 redundancy
You can configure VSRP to provide redundancy for Layer 2 only or both for Layer 2 and Layer 3:
Layer 2 only – The Layer 2 links are backed up but specific IP addresses are not backed up.
Layer 2 and Layer 3 – The Layer 2 links are backed up and a specific IP address is also backed up. Layer 3 VSRP is the same as VRRPE. However, using VSRP provides redundancy at both layers at the same time.
Master election and failover
Each VSRP device advertises its VSRP priority in Hello messages. During Master election, the VSRP device with the highest priority for a given VRID becomes the Master for that VRID. After Master election, the Master sends Hello messages at regular intervals to inform the Backups that the Master is healthy.
If there is a tie for highest VSRP priority, the tie is resolved as follows:
VSRP failover
Each Backup listens for Hello messages from the Master. The Hello messages indicate that the Master is still available. If the Backups stop receiving Hello messages from the Master, the election process occurs again and the Backup with the highest priority becomes the new Master.
Each Backup waits for a specific period of time, the Dead Interval, to receive a new Hello message from the Master. If the Backup does not receive a Hello message from the Master by the time the Dead Interval expires, the Backup sends a Hello message of its own, which includes the Backup's VSRP priority, to advertise the Backup's intent to become the Master. If there are multiple Backups for the VRID, each Backup sends a Hello message.
When a Backup sends a Hello message announcing its intent to become the Master, the Backup also starts a hold-down timer. During the hold-down time, the Backup listens for a Hello message with a higher priority than its own:
If the Backup does not receive a Hello message with a higher priority than its own by the time the hold-down timer expires, the Backup becomes the new Master and starts forwarding Layer 2 traffic on all ports.
VSRP priority calculation
Each VSRP device has a VSRP priority for each VRID and its VLAN. The VRID is used during Master election for the VRID. By default, a device’s VSRP priority is the value configured on the device (which is 100 by default). However, to ensure that a Backup with a high number of up ports for a given VRID is elected, the device reduces the priority if a port in the VRID’s VLAN goes down. For example, if two Backups each have a configured priority of 100, and have three ports in VRID 1 in VLAN 10, each Backup begins with an equal priority, 100. This is shown in Figure 76
Figure 76 VSRP priority
However, if one of the VRID’s ports goes down on one of the Backups, that Backup’s priority is reduced. If the Master’s priority is reduced enough to make the priority lower than a Backup’s priority, the VRID fails over to the Backup. Figure 77 shows an example.
Figure 77 VSRP priority recalculation
You can reduce the sensitivity of a VSRP device to failover by increasing its configured VSRP priority. For example, you can increase the configured priority of the VSRP device on the left in Figure 77 to 150. In this case, failure of a single link does not cause failover. The link failure caused the priority to be reduced to 100, which is still equal to the priority of the other device. This is shown in Figure 78.
Figure 78 VSRP priority bias
Track ports
Optionally, you can configure track ports to be included during VSRP priority calculation. In VSRP, a track port is a port that is not a member of the VRID’s VLAN, but whose state is nonetheless considered when the priority is calculated. Typically, a track port represents the exit side of traffic received on the VRID ports. By default, no track ports are configured.
When you configure a track port, you assign a priority value to the port. If the port goes down, VSRP subtracts the track port’s priority value from the configured VSRP priority. For example, if the you configure a track port with priority 20 and the configured VSRP priority is 100, the software subtracts 20 from 100 if the track port goes down, resulting in a VSRP priority of 80. The new priority value is used when calculating the VSRP priority. Figure 79 shows an example.
Figure 79 Track port priority
In Figure 79, 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 80.
Figure 80 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 Interval + Hold-down Interval + (3 x Hello Interval))/10
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 + 3 + (3 x 1)/10 = .9 seconds(900 milliseconds)
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.

Virtual Switch Redundancy Protocol (VSRP) : Overview of Virtual Switch Redundancy Protocol (VSRP)