52)VLAN port assignments can be configured either of two
ways:
Static VLANs: The administrator statically configures VLAN
port assignment. VLAN memberships on the switch ports are assigned
on a port-by-port basis.
Dynamic VLANs: A VMPS (VLAN Management
Policy Server) can dynamically assign VLAN ports. The MAC address
of the node is used to determine the VLAN assignment. A separate
server or a Catalyst 5000 can function as a VMPS server. When a
frame arrives on a dynamic port at the switch, it queries the VMPS
for the VLAN assignment based on the source MAC address of the arriving
frame.
VLAN Transport Protocol (VTP) information can be distributed
throughout the network to all stations including servers, routers,
and switches.
The VLAN transport protocol are:
ISL : ISL (Inter
Switch Link) is the VLAN transport protocol used over Fast Ethernet
trunked link.
802.1 : 802.1 is the VLAN transport protocol used
over FDDI trunked link.
LANE : LAN Emulation (LANE) is the VLAN
transport protocol used across an ATM trunked link.
53)VLAN Trunk Protocol (VTP) is a layer 2 protocol that maintains VLAN configurations through a common administrative domain. Configurations are made to a VTP server, and are propagated across trunk lines to all switches in the VTP domain. VTP provides auto-intelligence for configuring switches across the network.
VLANs are typically configured on switch ports. However, note that a router is required to switch traffic between VLANs. A switch identifies the VLAN associated with a given frame and forwards the frame to associated ports. Separate VLANs for voice and data traffic improves the privacy and reliability of voice communication.
VLSM (Variable Length Subnet Masking) allows efficient use of IP addresses. Networks implemented with VLSM can be summarized more efficiently due to manual control. With a distance vector protocol such as RIP or IGRP, only one subnet mask value can be used on a network, as subnet mask values are not sent in routing updates.
54)VTP is a Layer 2 messaging protocol. It carries configuration
information throughout a single domain. VTP operates in one of three
modes:
1. Server mode
2. Client mode
3. Transparent mode
VTP Servers can create, modify, or delete VLANs and other configuration
parameters for the specified VLAN domain.
A VTP client can't
create, change, or delete VLANs.
A VTP transparent mode is used
when a switch is not required to participate in VTP, but only pass
the information to other switches. Transparent switches don't work
either as Server or clients.
Configurations made to a single
switch, called VTP server, are propagated across the switch fabric
under a single domain control. Other switches, configured as VTP
clients, learn the configuration information from the server. It
is important to know that, Cisco switches such as Catalyst 1900,
acting as VTP servers save the VLAN configuration information in
their Non volatile memory (NVRAM), whereas client keep the information
only in running configuration.
55)VTP is a Layer 2 messaging protocol. It carries configuration
information throughout a single domain. VTP operates in one of three
modes:
1. Server mode: VTP Servers can create, modify, or delete
VLANs and other configuration parameters for the specified VLAN
domain.
2. Client mode: A VTP client can't create, change, or
delete VLANs.
3. Transparent mode: A VTP transparent mode is
used when a switch is not required to participate in VTP, but only
pass the information to other switches. Transparent switches don't
work either as Server or clients.
VTP pruning is a technique that enhances the available network bandwidth by reducing the broadcast, multicast, and flooded unicast messages. These frames are not forwarded to network devices that don't have ports associated with a given VLAN. When VTP pruning is enabled, a switch forwards the flooded traffic across a link to another switch, only if that switch has ports associated with that VLAN.
56)When a bridge starts up, the bridge ID is set as root
ID. That is, it considers itself as the root bridge. However, while
exchanging BDPUs, if it comes across a BDPU that has a bridge ID
lower than its own, then the bridge corresponding to the BDPU is
considered as root bridge, and this information is propagated. The
bridge ID consists of the following:
1. 2-byte priority: The
default value on Cisco switches is 0X8000 (32,768), lower the priority,
higher the chances of becoming a root bridge.
2. MAC address:
The 6 byte MAC address of the bridge. Lower the MAC address, higher
the chances of becoming a root bridge.
Note that, the bridge
(or switch) with lowest value of 2-byte priority will become the
root bridge. If the priority value is same, then the bridge with
lowest value of 6-byte MAC address will become the root bridge.
When the sub-interfaces on a serial interface are to be configured
for Frame Relay, each sub interface needs to be assigned individual
DLCI. The following command assigns a dlci of 100 to any sub-interface
is:
R(config-if)# frame-relay interface-dlci 100
Note that
prior to issuing the above command get into proper sub interface
configuration mode, for example the command below enter sub-interface
(0.1) mode:
R(config)# interface serial0.1 point-to-point
57)When two or more routers are contending to be a DR
(designated Router) on a network segment, the router with the highest
OSPF priority will become the DR for that segment. The same process
is repeated for the BDR. In case of a tie, the router with the highest
RID will win. The default for the interface OSPF priority is one.
Remember that the DR and BDR concepts are per multiaccess segment.
Setting the ospf priority on an interface is performed using the
ip ospf priority <value> interface command.
A priority
value of zero indicates an interface which is not to be elected
as DR or BDR. The state of the interface with priority zero will
be DROTHER.
58)When you are configuring NAT, NAT should be enabled
on at least one inside and one outside interface. The command for
enabling NAT on inside interface is:
R(config-if)# ip nat inside
The command for enabling NAT on the outside interface is:
R(config-if)#
ip nat outside
Remember to enter into appropriate configuration
modes before entering the commands. Usually, the inside NAT will
be configured on an Ethernet interface, whereas the outside NAT
is configured on a serial interface.
The command
ip nat inside
source static <local ip> <global ip>
configures address
translation for static NAT.
The command
ip nat inside source
list <access-list-number> pool <name>
is used to
map the access-list to the IP NAT pool during the configuration
of Dynamic NAT.
59)Wild card masking:
Wild card masking is used to
permit or deny a group of addresses. For example, if we have a source
address 185.54.13.2 and want all the hosts on the last octet to
be considered, we use a wild card mask, 185.54.13.255.
Special
cases:
Host 185.54.13.2 is same as 185.54.13.2 with a wild card
mask of 0.0.0.0, considers only specified IP.
Any is equivalent
to saying 0.0.0.0 with a wild card mask of 255.255.255.255. This
means none of the bits really matter. All IP addresses need to be
considered for meeting the criteria.
You can use "show controllers serial [port number]" to see if the interface detects a DCE or DTE cable.
60)You use show vlan or show vlan <vlan#> command to see the configuration details of VLANs. The command "sh vlan" will display the configuration information for all VLANs, where as the command "sh vlan vlan#" shows only the configuration information pertaining to that vlan. For example, if you want to see the configuration information for vlan 2, you give the command "sh vlan 2".
Voice traffic should have priority over data traffic because any delay in receiving VOIP packets may result in poor audio quality at the VOIP phone. You can separate the VOIP traffic from regular traffic by using VLANs, and Switch.
