VTP allows allows a network network manager to configur configure ea switch so that it will propagate VLAN configurations to other switches in the network. The switch can be configured in the role of a VTP server or a VTP client. VTP only learns about normal-range normal-range VLANs (VLAN IDs 1 to 1005). Extended-range VLANs (IDs greater than 1005) are not supp suppor orted ted by VTP VTP..
VTP allows allows a network network manager to make makess changes on a switch that is configured as a VTP server. Basically ly,, the VTP server distr distributes ibutes and Basical synchronizes synchr onizes VLAN information to VTP-enabled VTP-enabled switches throughout the switched network, which minimizes the problems problems caused by by incorrect configurations and configuration inconsistencies.. inconsistencies stores VLAN configurations configurations in the VLAN VTP stores database called vlan.dat.
VTP Domain consists of one or more interconnected interconnected switches. share VLAN configuration configuration details using VTP All switches in a domain shar advertisements. A router or Lay Layer 3 switch defines the boundary of each domain.
VTP Advertisements Advertisements - VTP uses a hierar h ierarchy chy of advertisements to distribute and synchronize VLAN configurations configurations across across the network. network.
VTP Modes - A switch can be configured in one of three modes: server, client, or transparent.
VTP Server - VTP servers advertise the VTP domain VLAN information to other VTP-enabled switches in the same VTP domain. VTP servers store store the VLAN information for the entire domain in NVRAM. The server is where VLAN can created, deleted, or renamed for the domain.
VTP Client - VTP clients function the same way as VTP servers, but you cannot create, change, or delete del ete VLANs on a VTP client. clie nt. A VTP client only stores stores the VLAN information for the entire domain domain while the switch is on. reset deletes the VLAN information. A switch reset You ou must configure configure VTP client mode on a switch. Y
VTP Transpar Transparent ent - Transparent Transparent switch switches es forward f orward VTP advertisements adv ertisements to VTP clients c lients and VTP servers. ser vers. Transparent switches do not participate in VTP. are created, created, renamed, or deleted on transparent transparent VLANs that are switches are local to that switch only.
VTP Pruning-VTP pruning increases increases network network available bandwidth by restricting flooded traffic to those trunk links that the traffic must use to reach the destination devices. Without VTP pruning, a switch floods broadcast, multicast, and unknown unicast traffic across all trunk links within a VTP domain even though receiving switches might discard them.
VTP allows allows you you to separate separate your your network network into smaller management domains to help reduce VLAN management management.. configuring VTP An additional benefit of configuring domains is that it limits the extent to which configuration configu ration changes are propagated propagated in the network if an error occurs.
A VTP domain consists of one switch or sever several al interconnected inter connected switches sharing the same VTP domain name. A switch can be a member of only one VTP domain at a time.
VTP Domain Name Propogation Propogation
For a VTP server or client switch to participate in a VTP-ena VTP-enabled bled netw net work, it must be a part of the same domain. domain. When switches are in different VTP domains, they do not exchange VTP messages. mess ages. propagates opagates the VTP domain name A VTP server pr to all switches for f or you. you. Domain name pr propagation opagation uses thr th ree VTP components: servers, clients, and advertisements.
VTP Frame Encapsulation
A VTP frame frame consists of a of a header field and a message field. The VTP information is inserted into the data field of an Ethernet frame
he Ethernet frame is then encapsulated as a 802.1Q trunk frame (or ISL frame)
Each switch in the domain sends periodic per iodic advertisements adv ertisements out each trunk tr unk port to a reser eserved ved multicast multicas t address.
Destination MAC address -This address is set to 01-000C-CC-CC-CC, which is the reserved multicast address for all VTP messages. messages.
LLC field-Logical link contr control ol (LLC) field contains a destination service access point (DSAP) and a source service access point (SSAP) set to the value of AA. AA.
SNAP field-Subnetwork Access Protocol (SNAP) field has an OUI set to AAAA and type set to 2003. 2003 .
VTP header field- The contents vary depending on the VTP message type-summary, type-summary, subset, or request-but request-but it always alw ays contains these VTP fields:
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Domain name- Identifies the administrative domain for the switch. Domain name length- Length of the domain name. Version V ersion-- Set to eith either er VTP 1, VTP 2, or VTP 3. The Cisco 2960 switch only suppor supports ts VTP 1 and VTP 2. Configuration Configu ration revision revision number- The current configuration revision number on this switch.
VTP message message field-V field-Varie aries s depending on the message type. VTP Message Contents
The configuration revision number is a 32-bit number that indicates the level of revision for a VTP frame. frame. def ault configuration number number for a switch The default is zero. zero. a VLAN is added or remo removed ved,, the Each time a VLAN configuration revision number is incremented. con figuration ration Each VTP device tracks the VTP configu revision number that is assigned to it.
Summary Adv Advertisements ertisements •
The summary advertisement contains the VTP VTP domain name, the current revision number, and other VTP configuration details.
Summary advertisements are sent: Every 5 minutes by a VTP server or client to inform neighboring VTP-enabled switches of the current VTP configuration revision number for its VTP domain conf iguration has been made Immediately after a configuration
Subset Adv Advertisements ertisements - A subset advertisement adv ertisement contains VLAN information. advertisement ertisement Changes that trigger the subset adv include:
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Creating or deleting a VLAN Creating Suspending or activ activating ating a VLAN Changing the name of a VLAN Changing the MTU of a VLAN
It may take multiple subset advertisements to fully update the VLAN information. inf ormation.
Request Advertisements
When a request advertisement is sent to a VTP server ser ver in the same VTP domain, the VTP server responds by sending a summary advertisement and then a subset advertisement.. advertisement
Request advertisements are sent if: •
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The VTP domain name has been changed c hanged The switch receives a summary advertisement with a higher configuration revision number than its own A subset advertisement advertisement message is missed for some reason reason The switch has been reset
Server Mode - In server mode, you can create, modify, and delete VLANs for the entir ent ire e VTP domain. domain. VTP server mode is the default mode for a Cisco switch. advertise their VLAN configurations to other VTP servers advertise switches in the t he same VTP domain and synchr synchronize onize their VLAN configurations with other switches based on advertisements received over trunk links. keep track of updates updates through through a VTP servers keep configuration revision number. compare their Other switches in the same VTP domain compare configuration revision number with the revision number received from a VTP server to see if they need to synchronize synchr onize their VLAN database.
Client Mode If a switch is in client mode, you cannot create, change, or delete VLANs. inf ormation In addition, the VLAN configuration information that a VTP client c lient switch receives from a VTP server switch is stored in a VLAN database, not in NVRAM. Consequently ently,, VTP clients require less memor memory y Consequ than VTP servers. When a VTP client cl ient is i s shut do down wn and an d restarted, it sends a request advertisement to a VTP server for updated VLAN configur confi guration ation information. inf ormation.
Transparent Mode
Switches configur configured ed in transpar transparent ent mode forwar forward d VTP advertisements adv ertisements that t hat they receiv receive e on trunk tr unk ports to other switches in the network. transparent mode switches do not advertise advertise their VTP transparent VLAN configuration and do not synchronize synchronize their VLAN configuration with any other switch. Configure a switch in VTP transparent mode when you have hav e VLAN configurations conf igurations that have local significance and should not be shared with the rest of the network.
VTP pruning pre preven vents ts unnecessary flooding of broadcast information from one VLAN across all trunks in a VTP domain. switches to negotiate negotiate VTP pruning permits switches which VLANs are are assigned to ports at the other end of a trunk tr unk and, an d, hence, prun prune e the VLANs that are not assigned to ports on the remote switch. by default. def ault. Pruning is disabled by enabled using the vtp the vtp pruning VTP pruning is enabled global configur conf iguration ation command. You ou need to enable enable pruning on only only one VTP Y server switch in the domain.
Confirm that all of the switches you are are going to configure configur e have been set to their default settings. settings. Always ys reset the configuration revision number before Alwa installing a previously previously configured configured switch switc h into in to a VTP domain.
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Not resetting the configuration revision number allows for potential disruption in the VLAN configuration across the rest of the switches in the VTP domain.
Configure at least tw Configure t wo VTP server ser ver switches in your network. •
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Because only server switches can create, delete, and modify VLANs, you should make make sure sure that you you have have one backup VTP server in case the primary VTP server becomes disabled. If all the switches in the network are configured in VTP client mode, you cannot ca nnot create c reate new VLANs on the th e network. net work.
Configure Configur e a VTP domain on the th e VTP server ser ver.. •
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Configuring the VTP domain on the first switch enables VTP to start adv advertising ertising VLAN information. Other switches connected through trunk links receive receive the VTP domain information automatically through VTP advertisements.
If there is an existing VTP domain, make sure that you match the name exactly exactly.. VTP domain d omain names ar are e caseca sesensitive. If you are configuring a VTP password, ensure that the same password password is set on all switches switch es in the domain that need to be able to exchange VTP information. info rmation. •
Switches without a password or with the wrong password reject VTP advertisements. advertisements.
Ensure that all switches are configured to use the same VTP protocol protocol version. version. •
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VTP version 1 is not compatible compatible with VTP version version 2. By default, Cisco Catalyst 2960 switches run version 1 but are capable of running version 2. When the VTP version is set to version 2, all version 2 capable switches in the domain autoconfigure to use version 2 through the VTP announcement pr process. ocess.
Create the VLAN after you hav Create h ave e enabled e nabled VTP on the VTP server. •
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VLANs created created before you you enable VTP are are remov removed. ed. Always Alwa ys ensure ensure that trunk ports are are configured configured to interconnect interconnect switches in a VTP domain. VTP information is only exchanged exchanged on trunk ports.
As on the VTP server switch, confirm that the default settings are present.. present mode. Configure VTP client mode.
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Configure Configur e trunks trunks.. •
When you connect to a VTP server or another VTP-enabled switch, it takes a few moments for the various advertisements to make their way way back and forth to the VTP server. server.
Verify V erify VTP status. status. •
VTP works works over over trunk links.
Connect to a VTP server. server. •
Recall that the switch is not in VTP client mode by default. You have to configure this mode.
Before you begin configuring the access ports, confirm that the revision mode and number of VLANs have been updated.
Configure access ports Configure ports.. When a switch swi tch is i s in VTP client c lient mode, you cannot add new VLANs. •
You Y ou can only assign access access ports to existing VLANs.
