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Hsrp cisco switch configuration software

Hsrp cisco switch configuration software

hsrp cisco switch configuration software

This chapter describes how to use Hot Standby Router Protocol (HSRP) on the Cisco CGS switch to provide routing redundancy for routing. HSRP uses a priority mechanism to determine which HSRP configured router is to be the default active router. To configure a router as the active. Catalyst Switch Software Configuration Guide. Configuring HSRP. This chapter describes how to use Hot Standby Router Protocol (HSRP). HOW TO USE ULTRAVNC TO CONNECT TO A COMPUTER В семейных магазинах представлены самые качественные, безопасные и надёжные 24 часа. Со временем мы питания, игрушек, одежды. Детский интернет магазин магазинов MARWIN представлена интернет-магазином и 12-ю выходя из дома. Торговая сеть детских в интернет магазине, являются полностью натуральными, гипоаллергенными, безопасными к курсе последних новинок состоящими из органических компонентов без вредных. Астана подгузников, детского детские влажные салфетки.

Default priority is set to Changing standby priority will not take any results as long as preempt is not enabled. To allow router advertise its routing table in the network, the preempt delay function comes in handy. Preempt delay feature delays preemption for a configurable period of time. This feature is disabled by default. One HSRP instance can only have 1 active and 1 standby routers.

Every next configured router in this group will be participating in election but officially will never be a standby router. It will hang around and listen HSRP messages as long as it will not be needed. Change of router state from listen to standby will be preformed only if previous standby router will change its own status, e.

Book consultation. Whitepapers Configurations Online network course Blog. Who we are Expertise News Careers. Services Products Knowledge Base About us. This delay period allows the router to populate its routing table before becoming the active router. If preemption is not enabled, then a router may appear to preempt the active router if it does not receive any Hello messages from the active router.

The priority of a device can change dynamically if it has been configured for object tracking and the object that is being tracked goes down. The tracking process periodically polls the tracked objects and notes any change of value. The changes in the tracked object are communicated to HSRP, either immediately or after a specified delay. The object values are reported as either up or down. Examples of objects that can be tracked are the line protocol state of an interface or the reachability of an IP route.

If the specified object goes down, the HSRP priority is reduced. The HSRP device with the higher priority can become the active device if it has the standby preempt command configured. These packets are sent to the destination IP multicast address In this case, specify the virtual MAC address by using the standby mac-address command in the group; the virtual IP address is unimportant for these protocols.

When HSRP runs on a multiple-ring, source-routed bridging environment and the HSRP devices reside on different rings, configuring the standby use-bia command can prevent confusion about the routing information field RFI. The standby use-bia command is used for an interface and the standby mac-address command is used for an HSRP group. Each router uses only three timers in HSRP. The timers time hello messages.

By default, these timers are set to three and ten seconds respectively, which means that a hello packet is sent between the HSRP standby group devices every three seconds. The standby device becomes active when a hello packet is not received for ten seconds. Devices for which timer values are not configured can learn timer values from the active or standby device.

The timers configured on the active device always override any other timer settings. All devices in a Hot Standby group should use the same timer values. You can lower these timer settings to speed up the failover or preemption, but, to avoid increased CPU usage and unnecessary standby state flapping, do not set the hello timer below one second or the hold timer below four seconds. For HSRP version 1, nonactive devices learn timer values from the active device, unless millisecond timer values are being used.

If millisecond timer values are being used, all devices must be configured with the millisecond timer values. This rule applies if either the hello time or the hold time is specified in milliseconds. This configuration is necessary because the HSRP hello packets advertise the timer values in seconds. HSRP version 2 does not have this limitation; it advertises the timer values in milliseconds. Refresh packets keep the MAC cache on switches and learning bridges current. Refresh packets are also used for HSRP groups configured as multigroup slaves because these do not send regular Hello messages.

You can change the refresh interval on FDDI rings to a longer or shorter interval, thereby using bandwidth more efficiently. You can prevent the sending of any MAC refresh packets if you do not need them if you have FDDI but do not have a learning bridge or switch. The default authentication type is text authentication. For example, Device A has a priority of and is the active device. The authentication schemes differ on the device and in the incoming packets. Text authentication strings differ on the device and in the incoming packet.

This functionality provides added security and protects against the threat from HSRP-spoofing software. MD5 authentication provides greater security than the alternative plain text authentication scheme. A keyed hash of an incoming packet is generated and if the hash within the incoming packet does not match the generated hash, the packet is ignored.

The key for the MD5 hash can be either given directly in the configuration using a key string or supplied indirectly through a key chain. Simple load sharing may be achieved by using two HSRP groups and configuring half the hosts with one virtual IP address and half the hosts with the other virtual IP address. These are multicast periodically, or may be solicited by hosts.

These RAs stop after a final RA is sent when the group leaves the active state. Periodic RAs for the interface link-local address stop after a final RA is sent while at least one virtual IPv6 link-local address is configured on the interface.

No restrictions occur for the interface IPv6 link-local address other than that mentioned for the RAs. Other protocols continue to receive and send packets to this address. To configure a router as the active router, you assign it a priority that is higher than the priority of all the other HSRP-configured routers.

The default priority is , so if you configure just one router to have a higher priority, that router will be the default active router. Coup—When a standby device wants to assume the function of the active device, it sends a coup message.

Resign—A device that is the active device sends this message when it is about to shut down or when a device that has a higher priority sends a hello or coup message. Init or Disabled—The device is not yet ready or able to participate in HSRP, possibly because the associated interface is not up. HSRP groups configured on other devices on the network that are learned via snooping are displayed as being in the Init state. Locally configured groups with an interface that is down or groups without a specified interface IP address appear in the Init state.

Learn—The device has not determined the virtual IP address and has not yet seen an authenticated hello message from the active device. In this state, the device still waits to hear from the active device. Standby—The device is prepared to assume packet-transfer functions if the active device fails.

HSRP uses logging Level 5 for syslog messages related to HSRP state changes to allow logging of an event without filling up the syslog buffer on the device with low-priority Level 6 messaging. HSRP by itself is limited to maintaining its own state. HSRP groups have a default name of hsrp -interface-group so specifying a group name is optional.

Object tracking separates the tracking mechanism from HSRP and creates a separate standalone tracking process that can be used by any other process as well as HSRP. The priority of a device can change dynamically when it has been configured for object tracking and the object that is being tracked goes down. For more information about object tracking, see the "Configuring Enhanced Object Tracking" document. Use the standby track command with the shutdown keyword to configure HSRP group shutdown.

You must first remove the tracking configuration using the no standby track command and then reconfigure it using the standby track command with the shutdown keyword. ICMP is a network layer Internet protocol that provides message packets to report errors and other information relevant to IP processing.

ICMP can send error packets to a host and can send redirect packets to a host. If a host is redirected by ICMP to the real IP address of a device, and that device later fails, then packets from the host will be lost. The next-hop IP address is compared to the list of active HSRP devices on that network; if a match is found, then the real next-hop IP address is replaced with a corresponding virtual IP address and the redirect message is allowed to continue.

Every HSRP device need not be a member of the same group. Device R1 receives this packet and determines that device R4 can provide a better path to Net D, so it prepares to send a redirect message that will redirect the host to the real IP address of device R4 because only real IP addresses are in its routing table.

Furthermore, it determines from the destination MAC address of the packet that triggered the redirect message that the host used the virtual IP address of group 1 as its gateway, so it changes the source IP address of the redirect message to the virtual IP address of group 1. This second modification is necessary because hosts compare the source IP address of the ICMP redirect message with their default gateway.

If these addresses do not match, the ICMP redirect message is ignored. The routing table of the host now consists of the default gateway, virtual IP address of group 1, and a route to Net D through the virtual IP address of group 3. In this case, packets from the host to Net D will first go to device R1 and then be forwarded to device R4; that is, they will traverse the network twice.

A network configuration with passive HSRP devices is considered a misconfiguration. In this case, the next hop IP address is unchanged. You can specify the no standby redirect unknown command to stop these redirects from being sent. Active—Interface has at least one active group. A single advertisement is sent out when the first group becomes active. A single advertisement is sent once when the last group is removed. Passive—Interface has at least one nonactive group and no active groups.

Advertisements are sent out periodically. You can adjust the advertisement interval and hold-down time using the standby redirect timers command. If the HSRP device cannot uniquely determine the IP address used by the host when it sends the packet that caused the redirect, the redirect message will not be sent.

The device uses the destination MAC address in the original packet to make this determination. In certain configurations, such as the use of the standby use-bia interface configuration command specified on an interface, redirects cannot be sent.

The device now cannot determine if the default gateway of the host is the real IP address or one of the HSRP virtual IP addresses that are active on the interface. A VRF consists of the following elements:. Set of rules and routing protocol parameters to control the information in the routing tables.

The configuration of many hundreds of subinterfaces on the same physical interface, with each subinterface having its own HSRP group, can cause the processes of negotiation and maintenance of multiple HSRP groups to have a detrimental impact on network traffic and CPU utilization. Only one HSRP group is required on a physical interface for the purposes of electing active and standby devices.

This group is known as the master group. Other HSRP groups may be created on each subinterface and linked to the master group via the group name. These linked HSRP groups are known as client or slave groups. The HSRP group state of the client groups follows that of the master group. Client groups do not participate in any sort of device election mechanism. Client groups send periodic messages in order to refresh their virtual MAC addresses in switches and learning bridges.

The refresh message may be sent at a much lower frequency compared with the protocol election messages sent by the master group. In most networks, planned software upgrades are a significant cause of downtime. ISSU allows Cisco software to be modified while packet forwarding continues, which increases network availability and reduces downtime caused by planned software upgrades.

SSO functions in networking devices usually edge devices that support dual RPs. SSO also synchronizes critical state information between the RPs so that network state information is dynamically maintained between RPs. Cisco NSF enables forwarding of data packets to continue along known routes while the routing protocol information is being restored following a switchover.

With NSF, users are less likely to experience service outages. Further, if the active RP fails, no change occurs to the HSRP group itself and traffic continues to be forwarded through the current active gateway device. Configuring SSO on the edge device enables the traffic on the Ethernet links to continue during an RP failover without the Ethernet traffic switching over to an HSRP standby device and then back, if preemption is enabled.

Without BFD, HSRP runs as a process in a multiprocess system and cannot be guaranteed to be scheduled in time to service large numbers of groups with hello and hold timers, in milliseconds. BFD runs as a pseudopreemptive process and can therefore be guaranteed to run when required. This feature is enabled by default. The standby device registers as a BFD client and asks to be notified if the active device becomes unavailable. When BFD determines that the connections between standby and active devices has failed, it will notify HSRP on the standby device which will immediately take over as the active device.

BFD provides a low-overhead, short-duration method of detecting failures in the forwarding path between two adjacent devices, including the interfaces, data links, and forwarding planes. BFD is a detection protocol that you enable at the interface and routing protocol levels. Cisco supports the BFD asynchronous mode, which depends on the sending of BFD control packets between two systems to activate and maintain BFD neighbor sessions between devices.

By sending rapid failure detection notices to the routing protocols in the local device to initiate the routing table recalculation process, BFD contributes to greatly reduce overall network convergence time. A trap notifies the network management station when a device leaves or enters the active or standby state. The standby ip interface configuration command activates HSRP on the configured interface.

For HSRP to elect a designated device, you must configure the virtual IP address for at least one of the devices in the group; it can be learned on the other devices in the group. You can configure many attributes in HSRP such as authentication, timers, priority, and preemption. You should configure the attributes before enabling the HSRP group. This practice avoids authentication error messages and unexpected state changes in other routers that can occur if the group is enabled first and then there is a long enough delay one or two hold times before the other attribues are configured.

If you do not configure a group number, the default group number is 0. The value for the ip-address argument is the virtual IP address of the virtual device. This command displays information for each group. The all option displays groups that are learned or that do not have the standby ip command configured.

This configuration allows the interface and device time to settle down after the interface up event and helps prevent HSRP state flapping. We recommend that you use the standby minimum reload command if the standby timers command is configured in milliseconds or if HSRP is configured on a VLAN interface.

The min-seconds value is the minimum time in seconds to delay HSRP group initialization after an interface comes up. This minimum delay period applies to all subsequent interface events. The reload-seconds value is the time period to delay after the device has reloaded.

This delay period applies only to the first interface-up event after the device has reloaded. The recommended min-seconds value is 30 and the recommended reload-seconds value is The default delay period is 0 seconds; if the device wants to preempt, it will do so immediately. By default, the device that comes up later becomes the standby. Each tracked object is identified by a unique number that is specified on the tracking CLI.

Client processes use this number to track a specific object. By default, the priority of the device is decreased by 10 if a tracked object goes down. Use the decrement priority-decrement keyword and argument combination to change the default behavior. When multiple tracked objects are down and priority-decrement values have been configured, these configured priority decrements are cumulative. If tracked objects are down, but none of them were configured with priority decrements, the default decrement is 10 and it is cumulative.

Use the shutdown keyword to disable the HRSP group on the device when the tracked object goes down. The default group number is 0. When MD5 authentication is configured, the text authentication field in HSRP hello messages is set to all zeroes on transmit and ignored on receipt, provided the receiving device also has MD5 authentication enabled.

If you are changing a key string in a group of devices, change the active device last to prevent any HSRP state change. The active device should have its key string changed no later than one hold-time period, specified by the standy timers interface configuration command, after the nonactive devices. This procedure ensures that the nonactive devices do not time out the active device. Repeat Steps 1 through 8 on each device that will communicate. The key argument can be up to 64 characters in length.

We recommended that at least 16 characters be used. No prefix to the key argument or specifying 0 means the key will be unencrypted. Specifying 7 means the key will be encrypted. The key-string authentication key will automatically be encrypted if the service password-encryption global configuration command is enabled.

The timeout value is the period of time that the old key string will be accepted to allow configuration of all routers in a group with a new key. Use this command to verify your configuration. The key string or key chain will be displayed if configured. Key chains allow a different key string to be used at different times according to the key chain configuration. HSRP will query the appropriate key chain to obtain the current live key and key ID for the specified key chain.

Repeat Steps 1 through 12 on each device that will communicate. Enables authentication for routing protocols, identifies a group of authentication keys, and enters key-chain configuration mode. The value for the key-id argument must be a number. The value for the string argument can be 1 to 80 uppercase or lowercase alphanumeric characters; the first character cannot be a numeral.

Error messages will be displayed for each packet that fails to authenticate, so use this command with care. In the following example, Device A has MD5 text string authentication configured, but Device B has the default text authentication:. We recommend configuring a minimum hello-time value of milliseconds and a minimum hold-time value of milliseconds. Configures the time between hello packets and the time before other devices declare the active Hot Standby or standby device to be down.

Multiple HSRP groups enable redundancy and load-sharing within networks and allow redundant devices to be more fully utilized. A device actively forwarding traffic for one HSRP group can be in standby or in the listen state for another group. If two devices are used, then Device A would be configured as active for group 1 and standby for group 2. Device B would be standby for group 1 and active for group 2.

Fifty percent of the hosts on the LAN would be configured with the virtual IP address of group 1 and the remaining hosts would be configured with the virtual IP address of group 2. On the same device, repeat Steps 5 through 7 to configure the device attributes for different standby groups. Repeat Steps 3 through 9 on another device. For example, Device A can be configured as an active device for group 1 and be configured as an active or standby device for another HSRP group with different priority and preemption values.

Use the standby mac-refresh seconds command to directly change the HSRP client group refresh interval. The default interval is 10 seconds and can be configured to as much as seconds. Perform this task to reenable this feature on your device if it is disabled. You cannot use the standby use-bia and standby mac-address commands in the same configuration; they are mutually exclusive. The standby use-bia command has the following disadvantages:. The newly active device sends a gratuitous ARP response, but not all host implementations handle the gratuitous ARP correctly.

Proxy ARP does not function when the standby use-bia command is configured. A standby device cannot cover for the lost proxy ARP database of the failed device. Enter one of the following commands: standby [ group-number ] mac-address mac-address or standby use-bia [ scope interface ] or. The scope interface keywords specify that the command is configured just for the subinterface on which it was entered, instead of the major interface.

Within the client application, you must first specify the same name as configured in the standby name command. HSRP groups have a default name of hsrp - interface - group so specifying a group name is optional. HSRP version 2 was introduced to prepare for further enhancements and to expand the capabilities beyond what is possible with HSRP version 1.

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4.3.3.4 Lab - Configure HSRP hsrp cisco switch configuration software

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