What is vrrp pdf

The default priority value for VRRP routers backing up a virtual router is decimal. The priority value zero 0 has special meaning indicating that the current Master has stopped participating in VRRP.

This is used to trigger Backup routers to quickly transition to Master without having to wait for the current Master to timeout. Authentication Type The authentication type field identifies the authentication method being utilized. Authentication type is unique on a Virtual Router basis.

The authentication type field is an 8 bit unsigned integer. A packet with unknown authentication type or that does not match the locally configured authentication method MUST be discarded.

These were removed in this specification because operational experience showed that they did not provide any real security and would only cause multiple masters to be created. The authentication methods currently defined are: 0 - No Authentication 1 - Reserved 2 - Reserved 5. The contents of the Authentication Data field should be set to zero on transmission and ignored on reception. Authentication Type 1 - Reserved This authentication type is reserved to maintain backwards compatibility with RFC Authentication Type 2 - Reserved This authentication type is reserved to maintain backwards compatibility with RFC The default is 1 second.

This field is used for troubleshooting misconfigured routers. The checksum is the bit one's complement of the one's complement sum of the entire VRRP message starting with the version field. For computing the checksum, the checksum field is set to zero. The number of addresses included is specified in the "Count IP Addrs" field. These fields are used for troubleshooting misconfigured routers.

Authentication Data The authentication string is currently only used to maintain backwards compatibility with RFC Protocol State Machine 6. The value of decimal is reserved for the router that owns the IP addresses associated with the virtual router.

The range decimal is available for VRRP routers backing up the virtual router. The default value is decimal. Configured item. No default. Default is 1 second. Values are True to allow preemption and False to prohibit preemption. Default is True. Note: Exception is that the router that owns the IP address es associated with the virtual router always preempts independent of the setting of this flag.

Values are defined in section 5. A VRRP router implements an instance of the state machine for each virtual router election it is participating in. Initialize The purpose of this state is to wait for a Startup event.

If the packet was not generated by the address owner Priority does not equal decimal , the receiver MUST drop the packet, otherwise continue processing. The next two octets indicate the address block assigned to the VRRP protocol. This mapping provides for up to VRRP routers on a network. Operational Issues 8. This allows VRRP to be used in environments where the topology is not symmetric.

The IP source address of an ICMP redirect should be the address the end host used when making its next hop routing decision. If a VRRP router is acting as Master for virtual router s containing addresses it does not own, then it must determine which virtual router the packet was sent to when selecting the redirect source address. One method to deduce the virtual router used is to examine the destination MAC address in the packet that triggered the redirect. It may be useful to disable Redirects for specific cases where VRRP is being used to load share traffic between a number of routers in a symmetric topology.

This allows the client to always use the same MAC address regardless of the current Master router. Forwarding these packets would result in unnecessary traffic.

Also in the case of LANs that receive packets they transmit e. Under some conditions, such as router isolations, ring failures, protocol transitions, etc. These include: - In order to switch to a new master located on a different bridge token ring segment from the previous master when using source route bridges, a mechanism is required to update cached source route information.

While many newer token ring adapters support group addresses, token ring functional address support is the only generally available multicast mechanism. Due to the limited number of token ring functional addresses these may collide with other usage of the same token ring functional addresses. Token ring functional addresses have the two high order bits in the first MAC address octet set to B'1'. They range from to canonical format. However, unlike multicast addresses, there is only one unique functional address per bit position.

However, since there are only 12 user-defined token ring functional addresses, there may be other non-IP protocols using the same functional address. In general, token ring VRRP users will be responsible for resolution of other user- defined token ring functional address conflicts. VRIDs are mapped directly to token ring functional addresses. In order to decrease the likelihood of functional address conflicts, allocation will begin with the largest functional address.

This is not a problem for bridges since packets addressed to functional addresses will be sent on the spanning-tree explorer path [ Additionally, routers MAY support unicast mode of operation to take advantage of newer token ring adapter implementations that support non-promiscuous reception for multiple unicast MAC addresses and to avoid both the multicast traffic and usage conflicts associated with the use of token ring functional addresses.

However, one important difference exists. Hence, these implementations need to receive a packet with the virtual MAC address as the source address in order to transmit to that MAC address in a source-route bridged network. Unicast mode on token ring has one limitation that should be considered. If there are VRID routers on different source-route bridge segments and there are host implementations that keep their source-route information in the ARP cache and do not listen to gratuitous ARPs, these hosts will not update their ARP source-route information correctly when a switch-over occurs.

The only possible solution is to put all routers with the same VRID on the same source-bridge segment and use techniques to prevent that bridge segment from being a single point of failure. Methods Citations. Topics from this paper. Router computing Internet. Failover Routing.

Citation Type. Has PDF. Publication Type. More Filters. View 1 excerpt, cites background. An evaluation of the virtual router redundancy protocol extension with load balancing.

An evaluation of the Virtual Router Redundancy Protocol extension with multi segment load balancing. View 2 excerpts, cites methods and background. Cluster-based virtual router. Preempt Mode. It is placed in all VRRP advertisement messages sent by each virtual router.

A higher priority value defines a greater priority in becoming the virtual router master for the VRID. The priority value can only be configured when the defined IP address on the IP interface is different than the virtual router IP address non-owner mode. When the IP address on the IP interface matches the virtual router IP address owner mode , the priority value is fixed at , the highest value possible.

This virtual router member is considered the owner of the virtual router IP address. There can only be one owner of the virtual router IP address for all virtual router members. The priority value 0 is reserved for VRRP advertisement message purposes. It is used to tell other virtual routers in the same VRID that this virtual router is no longer acting as master, triggering a new election process.

When this happens, each backup virtual router sets its master down timer equal to the skew time value. This shortens the time until one of the backup virtual routers becomes master. This prevents another backup from becoming master for a short period of time. Non-owner virtual routers may be configured with a priority of through 1.

The default value is Multiple non-owners can share the same priority value. When multiple non-owner backup virtual routers are tied transmit VRRP advertisement messages simultaneously in the election process, both become master simultaneously, the one with the best priority will win the election.

The higher IP address becomes master. The priority is also used to determine when to preempt the existing master. If the preempt mode value is true, VRRP advertisement messages from inferior lower priority masters are discarded, causing the master down timer to expire and the transition to master state.

The priority value also dictates the skew time added to the master timeout period. Multi-netting supports 16 IP addresses on the IP interface, up to 16 addresses can be assigned to a specific a virtual router instance.

Each virtual router is configured with a message interval per VRID within which it participates. This parameter must be the same for every virtual router on the VRID. For IPv4, the default advertisement interval is 1 second and can be configured between milliseconds and seconds milliseconds.

For IPv6, the default advertisement interval is 1 second and can be configured between milliseconds and 40 seconds milliseconds. As specified in the RFC, the advertisement interval field in every received VRRP advertisement message must match the locally configured advertisement interval.

If a mismatch occurs, depending on the inherit configuration, the current master's advertisement interval setting can be used to operationally override the locally configured advertisement interval setting.

If the current master changes, the new master setting is used. If the local virtual router becomes master, the locally configured advertisement interval is enforced.

If a VRRP advertisement message is received with an advertisement interval set to a value different than the local value and the inherit parameter is disabled, the message is discarded without processing.

The master virtual router on a VRID uses the advertisement interval to load the advertisement timer, specifying when to send the next VRRP advertisement message. Each backup virtual router on a VRID uses the advertisement interval with the configured local priority to derive the master down timer value.

The skew time is used to add a time period to the master down interval. This is not a configurable parameter. To calculate the skew time, the virtual router evaluates the following formula:. The higher priority value, the smaller the skew time will be. This means that virtual routers with a lower priority will transition to master slower than virtual routers with higher priorities. The master down interval is a calculated value used to load the master down timer.

When the master down timer expires, the virtual router enters the master state. To calculate the master down interval, the virtual router evaluates the following formula:. The operational advertisement interval is dependent upon the state of the inherit parameter.

When inherit is disabled, the operational advertisement interval must be equal to the locally configured advertisement interval. The master down timer is only operational when the local virtual router is operating in backup mode.

Preempt mode is a true or false configured value which controls whether a specific backup virtual router preempts a lower priority master. The IP address owner will always become master when available. Preempt mode cannot be set to false on the owner virtual router. The default value for preempt mode is true. When preempt mode is true, a master non-owner virtual router will only allow itself to be preempted when the incoming VRRP advertisement message priority field value is one ot the following:.

Greater than the virtual router in-use priority value. Equal to the in-use priority value and the source IP address primary IP address is greater than the virtual router instance primary IP address. A backup router will only attempt to become the master router if the preempt mode is true and the received VRRP advertisement priority field is less than the virtual router in-use priority value. The authentication type parameter defines the type of authentication used by the virtual router in VRRP advertisement message authentication.

The current master uses the configured authentication type to indicate any egress message manipulation that must be performed in conjunction with any supporting authentication parameters before transmitting a VRRP advertisement message.

The configured authentication type value is transmitted in the message authentication type field with the appropriate authentication data field filled in. Backup routers use the authentication type message field value in interpreting the contained authentication data field within received VRRP advertisement messages.

VRRP supports three message authentication methods which provide varying degrees of security. The supported authentication types are:. The use of type 0 indicates that VRRP advertisement messages are not authenticated provides no authentication. The master transmitting VRRP advertisement messages will transmit the value 0 in the egress messages authentication type field and the authentication data field.

Backup virtual routers receiving VRRP advertisement messages with the authentication type field equal to 0 will ignore the authentication data field in the message. All compliant VRRP advertisement messages are accepted. IP header destination IP address — Must be IP header protocol field — must be decimal. Type field — Must be set to the value of 1 advertisement. Authentication type field — Must be equal to 0. VRRP messages not meeting the criteria are silently dropped. The use of type 1 indicates that VRRP advertisement messages are authenticated with a clear simple text password.

All virtual routers participating in the virtual router instance must be configured with the same 8 octet password. Transmitting virtual routers place a value of 1 in the VRRP advertisement message authentication type field and put the configured simple text password into the message authentication data field. Receiving virtual routers compare the message authentication data field with the local configured simple text password based on the message authentication type field value of 1.

The same checks are performed for type 0 with the following exceptions the VRRP specification may require additional checks :. Authentication type field — Must be equal to 1. Any VRRP message not meeting the type 0 verification checks with the exceptions above are silently discarded. Any received VRRP advertisement message that fails authentication must be silently discarded with an invalid authentication counter incremented for the ingress virtual router instance.

This feature is different than the VRRP advertisement message field with the same name. This is any required authentication information that is pertinent to the configured authentication type. The type of authentication data used for each authentication type is as follows:. Authentication Type Authentication Data. The MAC address configuration must be the same for all virtual routers participating as a virtual router or indeterminate connectivity by the attached IP hosts will result.

VRRP advertisement messages contain an IP address count field that indicates the number of IP addresses listed in the sequential IP address fields at the end of the message.

The Alcatel-Lucent routersimplementation always logs mismatching events. The decision on where and whether to forward the generated messages depends on the configuration of the event manager.

To facilitate the sending of mismatch log messages, each virtual router instance keeps the mismatch state associated with each source IP address in the VRRP master table.

Whenever the state changes, a mismatch log message is generated indicating the source IP address within the message, the mismatch or match event and the time of the event.

With secondary IP address support, multiple IP addresses may be found in the list and it should match the IP address on the virtual router instance.