Chap 4

1
Chap 4 Implement VTP Learning Objectives

• Explain the role of VTP in a converged switched
  network
• Describe the operation of VTP VTP domains, VTP
  Modes, VTP Advertisements, and VTP Pruning.
• Configure VTP on the switches in a converged
  network.

2
VLAN Trunking Protocol (VTP)

• Before discussing VTP, it is important to
  understand that VTP is
• not necessary in order to configure VLANs or
  Trunking on Cisco
• Switches.
• VTP is a Cisco proprietary protocol that allows
  VLAN configuration to be consistently maintained
  across a common administrative domain.
• VTP minimises the possible configuration
  inconsistencies that arise when changes are made.
• Additionally, VTP reduces the complexity of
  managing and monitoring VLAN networks, allowing
  changes on one switch to be propagated to other
  switches via VTP.
• On most Cisco switches, VTP is running and has
  certain defaults already configured.

3
VTP Operation
1. Create VLAN 40 on S1 VTP server

• VTP allows a network manager to makes changes on
  a switch that is configured as a VTP server. The
  VTP server distributes and synchronizes VLAN
  information to VTP-enabled switches throughout
  the switched network,

S1
VLAN 40
PC4 172.17.10.24/24
PC1 172.17.10.21/24
Fa0/1
Fa0/2
Fa0/11
Fa0/11
S2
S3
Fa0/2
Fa0/1
Fa0/18
PC5 172.17.20.25/24
Fa0/18
PC2 172.17.20.22/24
VLAN 40
Fa0/6
Fa0/6
2. VTP propagates VLAN 40 to S2 S3 VTP clients
PC6 172.17.30.26/24
PC3 172.17.30.23/24
VTP stores VLAN configurations in the VLAN
database called vlan.dat.
4
VTP Components

• VTP Domain - consists of one or more
  interconnected switches. All switches in a domain
  share VLAN configuration details using VTP
  advertisements. A router or Layer 3 switch
  defines the boundary of each domain.
• VTP Advertisements - used to distribute and
  synchronize VLAN configurations across the
  network.
• VTP Modes - a switch can be configured in one of
  three modes server, client, or transparent.
• VTP Server - 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 VLANs on a VTP client. A VTP client only
  stores the VLAN information for the entire domain
  while the switch is on. A switch reset deletes
  the VLAN information.
• VTP Transparent - forwards VTP advertisements to
  VTP clients and VTP servers, but do not
  participate in VTP. VLANs that are created,
  renamed, or deleted on transparent switches are
  local to that switch only.
• VTP Pruning - VTP pruning increases network
  available bandwidth by restricting flooded
  traffic to those trunk links that the traffic
  must use to reach the destination devices.

5
Default VTP Configuration
Sh vtp status
6
VTP Domains

• VTP allows separation of a network into smaller
  management domains to help reduce VLAN management

• Until the VTP domain name is specified, VLANs
  cannot be created or modified on a VTP server,
  and VLAN information is not propagated over the
  network.

S4
S5
S6
7
VTP Domain Name Propagation

1. The network manager configures the VTP domain
   name as cisco2 on the VTP server switch S1.
2. The VTP server sends out a VTP advertisement with
   the new domain name embedded inside.
3. The S2 and S3 VTP client switches update their
   VTP configuration to the new domain name.

cisco2
S1
Server
Null0
cisco2
VTP Advert
VTP Advert
S2
S3
Client
Client
Null0
Null0
cisco2
cisco2
8
VTP Frame Structure

• A VTP frame consists of a header field and a
  message field. The VTP information is inserted
  into the data field of an Ethernet frame. The
  Ethernet frame is then encapsulated as a 802.1Q
  trunk frame (or ISL frame).
• Each switch in the domain sends periodic
  advertisements out each trunk port to a reserved
  multicast address. These advertisements are
  received by neighboring switches, which update
  their VTP and VLAN configurations as necessary.

9
VTP Revision Number

• The configuration revision number is a 32-bit
  number that indicates the level of revision for a
  VTP frame.
• The default configuration number for a switch is
  zero.
• Each time a VLAN is added or removed, the
  configuration revision number is incremented.
  Each VTP device tracks the VTP configuration
  revision number that is assigned to it.

• Note A VTP domain name change does not increment
  the revision number. Instead, it resets the
  revision number to zero.

10
VTP Message Types

• Server and client switches issue summary
  advertisements every 5 minutes. Servers inform
  neighbor switches what they believe to be the
  current VTP revision number

• Clients request VLAN information from servers
  using the advertisement request.

• Subset advertisements contain detailed
  information about VLANs and are sent by servers
  in response to an advertisement request from a
  client.

11
VTP Operation - Server

• VTP servers can create, modify, delete VLAN and
  VLAN configuration parameters for the entire
  domain.
• VTP servers save VLAN configuration information
  in the switch NVRAM.
• VTP servers send VTP messages out to all trunk
  ports.

12
VTP Operation - Client

• VTP clients cannot create, modify, or delete VLAN
  information.
• The only role of VTP clients is to process VLAN
  changes and send VTP messages out all trunk
  ports.
• The VTP client maintains a full list of all VLANs
  within the VTP domain, but it does not store the
  information in NVRAM.
• Any changes made must be received from a VTP
  server advertisement.

13
VTP Operation - Transparent

• Switches in VTP transparent mode forward VTP
  advertisements but ignore information contained
  in the message.
• A transparent switch will not modify its database
  when updates are received, nor will the switch
  send out an update indicating a change in its own
  VLAN status.
• Except for forwarding VTP advertisements, VTP is
  disabled on a transparent switch.
• There is also an off VTP mode in which switches
  behave the same as in the VTP transparent mode,
  except VTP advertisements are not forwarded.

14
VTP Pruning

• VTP pruning prevents unnecessary flooding of
  broadcast information from one VLAN across all
  trunks in a VTP domain.
• VTP pruning permits switches to negotiate which
  VLANs are assigned to ports at the other end of a
  trunk and, hence, prune the VLANs that are not
  assigned to ports on the remote switch.
• Pruning is disabled by default. VTP pruning is
  enabled using the vtp pruning global
  configuration command on the VTP Server.

S1
PC4 VLAN 20
PC1 VLAN 10
Fa0/1
Fa0/2
Fa0/11
Fa0/11
S2
S3
Fa0/1
Fa0/2
Fa0/18
PC5 VLAN 20
Fa0/18
PC2 VLAN 20
Fa0/6
Fa0/6
PC6 VLAN 20
PC3 VLAN 10
15
VTP Pruning Enabled
S2 will no longer send VLAN 10 broadcasts out of
Fa0/1
S1
PC4 VLAN 20
PC1 VLAN 10
Fa0/1
Fa0/2
Fa0/11
Fa0/11
S2
S3
Fa0/1
Fa0/2
Fa0/18
PC5 VLAN 20
Fa0/18
PC2 VLAN 20
Fa0/6
Fa0/6
PC6 VLAN 20
PC3 VLAN 10
16
VTP Server Configuration
1. Check VTP revision number, mode, domain name
(Use reset vtp command to zeroise revision number)
Server
S1
PC1 VLAN 10
Fa0/1
Fa0/11
S2
Fa0/1
Fa0/2
Fa0/18
PC2 VLAN 20
Client
Fa0/6
2. Use vtp domain command to configure domain
name as cisco1
PC3 VLAN 30
17
VTP Server Configuration
3. Use vtp version command to set VTP version
(VTP 1 and VTP are not compatible)
Server
S1
PC1 VLAN 10
Fa0/1
Fa0/11
S2
Fa0/1
Fa0/2
Fa0/18
PC2 VLAN 20
Client
Fa0/6
4. Add VLANs, activate Fa0/1 trunk
PC3 VLAN 30
18
VTP Client Configuration
1. Check VTP revision number, mode, domain name
(Use reset vtp command to zeroise revision number)
Server
S1
PC1 VLAN 10
Fa0/1
Fa0/11
S2
Fa0/1
Fa0/2
Fa0/18
PC2 VLAN 20
2. Use vtp mode client command to configure S2 as
a client
Client
Fa0/6
PC3 VLAN 30
19
VTP Client Configuration
3. Check status of trunk and VTP parameters
Server
S1
PC1 VLAN 10
Fa0/1
Fa0/11
S2
Fa0/1
Fa0/2
Fa0/18
PC2 VLAN 20
Client
Fa0/6
3. Connect trunk cabling, Check VTP
advertisements being exchanged
PC3 VLAN 30
20
Troubleshooting VTP

• Incompatible VTP Versions - VTP versions 1 and 2
  are incompatible with each other. Modern Cisco
  Catalyst switches, such as the 2960, are
  configured to use VTP version 1 by default.
• VTP Password Issues - When using a VTP password
  to control participation in the VTP domain,
  ensure that the password is set correctly on all
  switches in the VTP domain.
• Incorrect VTP Domain Name - The VTP domain name
  is a key parameter that is set on a switch. An
  improperly configured VTP domain affects VLAN
  synchronization between switches. To avoid
  incorrectly configuring a VTP domain name, only
  set the VTP domain name on one VTP server switch.
• All Switches Set to VTP Client Mode - lose all
  ability to create, delete, and manage VLANs
  within a network. To avoid losing all VLAN
  configurations in a VTP domain, configure a
  second switch in the same domain as a VTP server.

21
Any Questions?
22
Lab Topology
Chapter 4.4.1 Basic VTP Config
S1
PC4 172.17.10.24/24
PC1 172.17.10.21/24
Fa0/1
Fa0/2
Fa0/11
Fa0/11
S2
S3
Fa0/1
Fa0/2
Fa0/18
PC5 172.17.20.25/24
Fa0/18
PC2 172.17.20.22/24
Fa0/6
Fa0/6
PC6 172.17.30.26/24
PC3 172.17.30.23/24