[image] The definition of a header and trailer that permits frame delivery over the link

[image] Support for synchronous and asynchronous WAN links

[image] A Type field that permits many protocols to pass over the link

[image] Authentication protocols; specifically, a clear-text PAP for low-security environments and CHAP for more robust security

[image] Control protocols for each higher-level protocol

Link Control Protocol (LCP): This control protocol focuses on the link itself and ignores Layer 3 protocols sent across the link

Network Control Protocol (NCP): This category of protocols functions in conjunction with a specific Layer 3 protocol sent across the link

R1(config)#username R2 password cisco
R1(config)#interface serial2/0
R1(config-if)#encapsulation ppp
R1(config-if)#ppp authentication chap

R1(config-if)#end

What are the significance of the username and password in PPP?

-The username commands are entries for the opposite router.

-And The password must match on each device.

What command is used to verify PPP config?

R1#show ip interface brief

R1#show interface serial2/0

R1(config)#interface multilink 1
R1(config-if)#encapsulation ppp
R1(config-if)#ppp multilink
R1(config-if)#ip address 10.1.1.1 255.255.255.0
R1(config-if)#ppp multilink group 1
R1(config-if)#exit

PPPoE provides a standard method of employing the authentication methods of the Point-to-Point Protocol (PPP) over an Ethernet network.

PPPoE allows authenticated assignment of IP addresses.

Often, PPPoE client and server are interconnected by Layer 2 bridging protocols running over a DSL or other broadband connection.

Active Discovery Phase—In this phase, the PPPoE client locates a PPPoE server, called an access concentrator. During this phase, a Session ID is assigned, and the PPPoE layer is established.

PPP Session Phase—In this phase, PPP options are negotiated and authentication is performed. When the link setup is completed, PPPoE functions as a Layer 2 encapsulation method, allowing data to be transferred over the PPP link within PPPoE headers.

• At system initialization, the PPPoE client establishes a session with the access concentrator by exchanging a series of packets.
• After the session is established, a PPP link is set up, which includes authentication using Password Authentication Protocol (PAP).
• When the PPP session is established, each packet is encapsulated in the PPPoE and PPP headers.

interface dialer 2
R1(config-if)#ip address negotiated
R1(config-if)#mtu 1492
R1(config-if)#encapsulation ppp
R1(config-if)#ppp chap hostname JohnS
R1(config-if)#ppp chap password cisco
R1(config-if)#dialer pool 1
R1(config-if)#interface fa0/0
R1(config-if)#no ip address
R1(config-if)#pppoe-client dial-pool-number 1
R1(config-if)#pppoe enable
R1(config-if)#no shutdown
R1(config-if)#end

• one method of creating tunnels through your network
• GRE creates an additional header used by GRE to perform tunneling.
• uses a new IP header that encapsulates the original packet
• GRE does not provide any encryption type services.
• If security is required, this can be added using IPsec (for example).

interface tunnel 0
R1(config-if)#ip address 172.16.1.1 255.255.255.0
R1(config-if)#tunnel mode gre ip
R1(config-if)#tunnel source serial2/0
R1(config-if)#tunnel destination 10.1.1.2

R1(config)#router ospf 1
R1(config-router)#network 172.16.1.0 0.0.0.255 area 0
R1(config-router)#end

How do you verify a GRE config?

R2#show ip interface brief

R2#show ip ospf neighbor

• The tunnel source reference to a local source interface requires that the interface have an IP address and be in the up/up state
• Referencing a local IP address for your tunnel source requires that the IP address exist on the router and the associated interface be in the up/up state
• If you reference the tunnel destination using an IP address, the router must have a matching route to that destination IP address
• If you reference the destination as a hostname, this hostname must be resolvable by the local device
• %TUN-5-RECURDOWN: Tunnel0 temporarily disabled due to recursive routing error

• The error message means that the GRE tunnel router has discovered a recursive routing problem.
• This condition is usually due to one of these causes:   1—a misconfiguration that causes the router to try to route to the tunnel destination address using the tunnel interface itself (recursive routing)2—a temporary instability caused by route flapping elsewhere in the network

Point-to-point: This simple WAN topology connects two devices over a single connection.

Hub-and-spoke: This WAN topology features a central hub device (typically at a network HQ for example) that makes WAN connections out to branch offices (the spokes).

Full-mesh: This WAN topology is the most expensive and complex to maintain since this topology has all devices making connections to all other devices; although it can be complex and expensive, notice it provides excellent redundancy of WAN paths through the network.

Single-vs dual-homed: These WAN topologies refer to making a connection to multiple ISPs versus a single ISP; a dual-homed configuration is very powerful since it means that an ISP can completely fail to be able to route traffic for the customer, but that customer can dynamically fail over to the surviving ISP.

Name at least four key characteristics of UDP

UDP is connectionless.

UDP has very little overhead.

UDP is often used for voice and video traffic forms.

UDP can multiplex using port numbers to work with   multiple applications.

Name at least four key characteristics of TCP

TCP is connection-oriented.

TCP has more overhead than UDP.

TCP uses features like flow control, sequencing and

    acknowledgements to ensure reliable and ordered 

    delivery of segments.

TCP can multiplex using port numbers to work with multiple applications.

list of examples of protocol identifiers from the IP header

1—ICMP

6—TCP

17—UDP

88—EIGRP

89—OSPF

50-ESP

47-GRE

Error recovery

[image] Flow control using windowing

[image] Connection establishment and termination

[image] Ordered data transfer

[image] Data segmentation

[image] Layer 2 switching

[image] Port security

[image] QoS classification and marking and trust boundaries

[image] Address Resolution Protocol (ARP) inspection

[image] Virtual access control lists (VACLs)

[image] Spanning tree

[image] Power over Ethernet (PoE) and auxiliary VLANs for VoIP

[image] Aggregation of LAN or WAN links

[image] Policy-based security in the form of access control lists (ACLs) and filtering

[image] Routing services between LANs and VLANs and between routing domains

[image] Redundancy and load balancing

[image] A boundary for route aggregation and summarization configured on interfaces toward the core layer

[image] Broadcast domain control

[image] Providing high-speed switching

[image] Providing reliability and fault tolerance

troubleshooting methodology

Problem isolation

Determining at what layer of the OSI model and on what devices and links the problem may exist

Documentation: It is critical to document the processes you use and the information you find

Resolve: This is, of course, your ultimate goal; you find the root cause of the problem after your problem isolation process, you document what has happened, and then you fix the root cause of the problem

Escalate: Should you not be able to fix the issue, there should be a written escalation process in your organization; this might involve even communicating to a third party that your company partners with in order to fix the issue.

Verify and monitor: Many times it might take time to carefully verify and monitor your solution to ensure the issue(s) are truly resolved; this text provides very important guidance on exact verification and monitoring procedures for various specific technologies.

1.  Bottom-up troubleshooting approach.
2.  Top-down approach
3.  Divide-and-conquer approach

Infrastructure Management: Network Programmability

The creation of a routing table is an example of what plane of operation on a Cisco device?

 Network Programmability

REST is an excellent example of what in SDN?

Network programmability

What is the job of the Control Plane?

on a Router It builds these things. Routing protocols, such as OSPF, help to create a routing table.

On  a switch, it builds a nice MAC address table

It is the raw forwarding mechanics of the devices

ACI

Application Centric Infrastructure (ACI)

 in SDN where you take the Control Plane intelligence needed and centrally locate it in a device called the controller.

in SDN where you take the Control Plane intelligence needed and centrally locate it in a device called the controller.

This device can then handle (very efficiently) all the Control Plane items while the other networking devices just handle the Data Plane tasks

What are API's?

(application programming interfaces).

 These are basically standardized languages for communications between devices.

Cisco likes to use REST-based APIs. This allows the fancy discovery and control of the network elements using the HTTPS protocol.

Northbound used for communication between the controller and Network Application thru REST-based APIs

Southbound is aided by a service abstraction layer in order to control the devices. Cisco likes to keep it simple—they use the  (CLI) and (SNMP). It is between the SAL and the Data Plane devices

Console logging

Monitor logging

Buffer logging

Alert

(Immediate action required)

What is syslog level 1?

Emergency

(system unusable)

What is syslog level 2?

Critical

(Critical Event)

What is syslog level 3?

Error

(Error Event)

What is syslog level 4?

Warning

(warning event)

What is syslog level 5?

Notification

(Normal)

What is syslog level 6?

Informational

(normal)

What is syslog level 7?

Debug

(Requested by user)

What does the following command do,

logging host 10.1.1.3?

1. Boot the device into ROMMON mode; this is accomplished with a break key during boot or the removal of flash memory.

2. The configuration register of the device is then set to ignore the startup-config file (a common configuration register setting for this is 0x2142); a sample ROMMON command for this is confreg 0x2142

3. Reboot the router

4. Enter privileged mode.

5. issue the command copy startup-config running-config.

6. Change the enable secret password

7. Set the configuration register back with config-reg 0x2102.

8. Copy the running-config to the startup-config with copy running-config startup-config.

is a secure method of moving configuration files or IOS images through the network. 

SCP uses Secure Shell (SSH) for data transfer and uses authentication and encryption. This ensures the authenticity and confidentiality of the information in transit. SCP runs over TCP port 22 by default.

command that allows the enactment of a new running-config without a reload of the device.

Note: this could work well when used in conjunction with the archive command to restore a previous version of the device’s configuration.

1. SYN: The client sends a SYN to the server.

2. SYN-ACK: In response, the server replies with     a SYN-ACK.

3. ACK: Finally, the client sends an ACK back to the server.

UDP is connectionless.

UDP has very little overhead.

UDP is often used for voice and video traffic forms.

UDP can multiplex using port numbers to work with multiple applications.

TCP is connection-oriented.

TCP has more overhead than UDP.

TCP uses features like flow control, sequencing and acknowledgements to ensure reliable and ordered delivery of segments.

TCP can multiplex using port numbers to work with multiple applications.

1—ICMP

6—TCP

17—UDP

88—EIGRP

89—OSPF

 Error recovery

 Flow control using windowing

 Connection establishment and termination

 Ordered data transfer

 Data segmentation

This layer provides workgroup/user access to the network; as a result, this layer is sometimes called the workstation layer.

Layer 2 switching

 Port security

 QoS classification and marking and trust boundaries

 Address Resolution Protocol (ARP) inspection

 Virtual access control lists (VACLs)

 Spanning tree

 Power over Ethernet (PoE) and auxiliary VLANs for VoIP

The layer provides policy-based connectivity and controls the boundary between the access and core layers.

Aggregation of LAN or WAN links

 Policy-based security in the form of access control lists (ACLs) and filtering

 Routing services between LANs and VLANs and between routing domains

 Redundancy and load balancing

 A boundary for route aggregation and summarization configured on interfaces toward the core layer

Tag control information (TCI): consists of the following:

[image]Priority code point (PCP): A three-bit field that refers  to the IEEE 802.1p class of service and maps to the frame priority level.

[image] Drop eligible indicator (DEI): A one-bit field that may be used separately or in conjunction with PCP to indicate frames eligible to be dropped in the presence of congestion.

[image] VLAN identifier (VID): A 12-bit field specifying the VLAN to which the frame belongs.

1. Switches use STP Bridge Protocol Data Units (BPDUs) to carry their bridge ID information. The device with the lowest bridge ID becomes the root bridge.
2. The bridge ID is an eight-byte value that is unique for each switch.
3. The bridge identifier(ID) consists of two parts, a two-byte priority value and a six-byte system ID. The six-byte system ID is based on the built-in MAC address for the switch.

a Layer 2 EtherChannel using the built-in and default dynamic method of using the Port Aggregation Protocol (PAgP)

Note: There are two settings possible here—auto and desirable

channel-group 2 mode desirable
Creating a port-channel interface Port-channel 2

Note: This mode uses Active or Passive settings

DISTSW1(config-if-range)#shutdown
DISTSW1(config-if-range)#channel-group 3 mode active

show etherchannel 3 summary

Note: how we create the port-channel interface first and assign it an IP address.

interface port-channel 1
DISTSW1(config-if)#no switchport
DISTSW1(config-if)#ip address 10.10.10.1 255.255.255.0
DISTSW1(config-if)#exit

interface range gi0/1 , gi0/3
DISTSW1(config-if-range)#no switchport
DISTSW1(config-if-range)#shutdown
DISTSW1(config-if-range)#channel-group 1 mode on
DISTSW1(config-if-range)#no shutdown