Review - Chapter 3 Flashcards
VLAN Classification
○ End-to-end (campus wide)
○ Local (geographic)
VLAN Mapping Classification
○ Port-centric (static)
○ Dynamic (MAC address based) with a VLAN Management Policy Server (VMPS)
VLAN Segmentation
Switches filter the broadcast from all the ports or devices that are not part of the same VLAN
Campus network design models
○ End-to-end VLANs
○ Local VLANs
End-to-end VLANs
A single VLAN that is associated with switch ports widely dispersed throughout an enterprise network on multiple switches
Local VLANs
Generally confined to a wiring closet; VLANs are local to a single access switch and connect via trunk to an upstream distribution switch
Reasons for Implementing End-to-End Design
- Grouping users
- Security
- Applying QoS
- Routing avoidance
- Special-purpose VLAN
- Poor design
Benefits of using local VLANs in enterprise campus architecture design
○ Deterministic traffic flow ○ Active redundant paths ○ High availability ○ Finite failure domain ○ Scalable design
VLAN Configuration Modes
- Database Mode
- Global Mode
- Assign Ports
VLAN Trunks
Point-to-point links that carry traffic for multiple VLANs across a single physical link between the two switches or any two devices
Architectural Advantages of 802.1Q/802.1p Over ISL
- Smaller frame overhead, thus more efficient (4 bytes to 30 bytes)
- Widely supported industry standard protocol
- Has the support for 802.1p fields for QoS
MTU
To process an 802.1Q tagged frame, a device must enable a maximum transmission unit (MTU) of 1522 or higher
Baby Giants
Frames that are larger than the standard MTU of 1500 bytes but less than 2000 bytes
ISL MTU
1548 bytes
802.1Q MTU
1522 bytes
Dynamic Trunking Protocol (DTP)
Used on trunk ports to negotiate the trunking state
DTP Modes
○ Desirable ○ Auto ○ On ○ Off ○ Nonegotiate
VLAN Ranges
- ISL: 1-1005
* 802.1Q: 1-4094
Two WLAN Implementations
○ Standalone WLAN based on autonomous access points (APs)
○ Controller-based WLAN based on controller-based APs and WLCs (Wireless LAN Controllers)
VLAN Trunking Protocol (VTP)
Used to distribute and synchronize information about VLAN databases configured throughout a switched network
VTP Messages
Transmitted only on trunks over the management VLAN (default: VLAN 1) every 5 minutes using Layer 2 multicast frame
VTP Domain
○ One switch or several interconnected switches sharing the same VTP environment
○ Switches can only be in one VTP domain at any time
○ Default: (until manually configured or it receives an advertisement for a domain over trunk link)
VTP Modes
○ Server
○ Transparent
○ Client
Server Mode (VTP)
○ Default mode
○ VLANs not propagated until management domain name is specified/learned
○ Changes are propagated to all switches in the VTP domain, transmitted out all trunk connections
Transparent Mode (VTP)
○ Doesn’t participate in VTP
○ VLAN configuration changes only affect the local switch (doesn’t propagate)
○ Does forward VTP advertisements received within the domain
Client Mode (VTP)
Transmits and receives VTP updates on trunks but cannot create, change, or delete VLANs
VTP Version 2 features offered that Version 1 doesn’t
□ Version-dependent transparent mode
□ Consistency check
□ Token ring support
□ Unrecognized type-length-value support
VTP Version 3 Properties
□ Extended VLAN support □ Domain name not auto learned □ Better security □ Better database propagation □ MST support
VTP Authentication
○ VTP password feature
○ Uses MD5 algorithm to encode passwords in 16-byte words
○ Passwords are case sensitive and can be 8-64 characters long
VTP Advertisements
○ Sent every 5 mins or whenever there is a change in VLAN configuration
○ Transmitted over native VLAN using multicast frame
○ Includes a configuration revision number incremented by 1 every time a VTP server modifies its VLAN information
VTP Bomb
Occurs when a VTP server with a higher revision (albeit loaded with potentially incorrect information) of the VTP database is inserted into the production VTP domain causing the loss of VLAN information on all switches in that VTP domain
VTP Message Types
○ Summary advertisement
○ Subnet advertisement
Summary Advertisement
○ 5 minute increments
○ Inform adjacent switches of the current VTP domain name and configuration revision number
○ Advertisement request is sent if the revision number of receiving switch is lower than the advertised revision number
Subnet Advertisement
○ The server where VLAN changes are made increments the configuration revision and issues a summary advertisement
○ Contains a list of VLAN information
○ If there are several VLANs, more than one subnet advertisement can be required to advertise all the VLANs
When do switches need a VTP advertisement?
If:
○ The switch has been reset
○ The VTP domain name has been changed
○ The switch has received a VTP summary advertisement with a higher configuration revision than its own
○ Upon receipt of an advertisement request, a VTP device sends a summary advertisement
EtherChannel
A technology that allows you to circumvent the bandwidth issue of heavily solicited links by creating logical links that are made up of several physical links
Pros of EtherChannel
○ Higher bandwidth ○ Load balancing ○ Redundancy ○ Simplified configuration ○ Up to 8 links
EtherChannel Link Speeds
○ Max 1600 Mbps (Fast)
○ Max 16 Gbps (Gig)
○ Max 160 Gbps (10 Gig)
EtherChannel Mechanisms
○ LACP: IEEE negotiation protocol
○ PAgP: Cisco negotiation protocol
○ Static persistence: no negotiation protocol
Link Aggregation Protocol (LACP)
○ Ensures that all ports in EtherChannel have the same type of configuration speed, duplex, and VLAN information
○ Up to 16 links can be assigned to an EtherChannel but only 8 can be active at a time (max number of active links varies between switches)
LACP Modes of Operation
○ Active: Enable LACP
○ Passive: Enable LACP only if an LACP device is detected
Port Aggregation Protocol (PAgP)
○ Provides the same negotiation benefits as LACP
○ Cisco proprietary
○ Ports with same capabilities are bundled together into an EtherChannel (only on ports that are configured for identical VLANs or trunking)
PAgP Modes of Operation
○ Desirable: Enable PAgP
○ Auto: Enable PAgP only if a PAgP device is detected
EtherChannel Guard
- Used to detect EtherChannel misconfigurations between the switch and a connected device
- Can be enabled using the spanning-tree etherchannel guard misconfig global config command (is enabled by default)
