How to Configure PPP on Cisco Router？

What is PPP?

Point-to-Point connection is one of the most common types of WAN connection. PPP connections are used to connect LANs to service provider WANs, and to connect LAN segments within an organization network. A LAN-to-WAN point-to-point connection is also referred to as a serial connection or leased-line connection, because the lines are leased from a carrier (usually a telephone company) and are dedicated for use by the company leasing the lines.

Simply, when you establish a connection to your ISP (Internet Service Provider) through a modem. The connection between the ISP and you make up two points on the network. Therefore, the protocol that is used for establishing this connectivity between the two of you is the Point-to-Point Protocol or the PPP.

Note:The default serial encapsulation method when you connect two Cisco routers is HDLC. This means, Cisco HDLC can only work with other Cisco devices. However, when you need to connect to a non-Cisco router, you should use PPP encapsulation. This is one of many advantages to using PPP it is not proprietary.

PPP can be used over twisted pair, fibre-optic lines, and satellite transmission. PPP provides transport over ATM, Frame Relay, ISDN and optical links. For security, PPP allows you to authenticate or secure connections using either Password Authentication Protocol (PAP) or the more effective Challenge Handshake Authentication Protocol (CHAP).

PPP is used to carry out the following functions

• Data Encapsulations: this is a method used to encapsulate multi-protocol datagrams. Different network-layer protocols are simultaneously transported and encapsulated over the same link, the flexibility of the PPP design enables it to be compatible to most supporting network devices.
• Link Control Protocol: The LCP is used to establish, configure, and test the data link connection. It’s flexible in handling different sizes of packets, detect a looped-back link, configuration errors, and terminate the link.
• Network Control Protocol: NCP is used for establishing and configuring different Network layer protocols. PPP enables the simultaneous use of multiple Network layer protocols.  Some of the more familiar NCPs are:

u      Internet Protocol Control Protocol

u      AppleTalk Control Protocol

u      Novell IPX Control Protocol

u      Cisco Systems Control Protocol

u      SNA Control Protocol

u      Compression Control Protocol.

How to configure PPP on Cisco Router？

You can configure point-to-point encapsulation, software compression, link quality monitoring, load balancing across links (multilinks) on R1, R2 and R3 serial interface below.

Before you actually configure PPP on a serial interface, we will look at the commands and the syntax of these commands as shown below. This series of examples shows you how to configure PPP and some of the options.

1. How to enable PPP on an Interface

To set PPP as the encapsulation method used by a serial or ISDN interface, use the encapsulation ppp interface configuration command.

The following example enables PPP encapsulation on serial interface 0/0/0:

R1#config t

R1(config)#interface se 0/0/0

R1(config-if)#encapsulation ppp

R1(config-if)#end

The encapsulation ppp command has no arguments, however, you must first configure the router with an IP routing protocol (RIP, EIGRP or OSPF) to use PPP encapsulation. You should recall that if you do not configure PPP on a Cisco routers, the default encapsulation for serial interfaces is HLDC.

2. How to configure Compression

You can configure point-to-point software compression on serial interfaces after you have enabled PPP encapsulation. Because this option invokes a software compression process, it can affect system performance. If the traffic already consists of compressed files (.zip, .tar, or .mpeg, for example), do not use this option.

To configure compression over PPP, enter the following commands:

R1(config)#interface serial 0/0/0

R1(config-if)#encapsulation ppp

R1(config-if)#compress [predictor | stac]

R1(config-if)#end

3. How to configure Link Quality Monitoring

One of the primary functions of LCP when establishing a PPP session includes testing of a link to determine whether the link quality is sufficient to use Layer 3 protocols. The command ppp quality {percentage} ensures that the link meets the quality requirement you set; otherwise, the link closes down.

How Link Percentage is calculated

The percentages are calculated for both incoming and outgoing directions. The outgoing quality is calculated by comparing the total number of packets and bytes sent to the total number of packets and bytes received by the destination node. The incoming quality is calculated by comparing the total number of packets and bytes received to the total number of packets and bytes sent by the destination node.

If the link quality percentage is not maintained, the link is deemed to be of poor quality and is taken down. Link Quality Monitoring (LQM) implements a time lag so that the link does not bounce up and down.

Use the configuration commands below to monitor the data traffic on the link and avoids frame looping:

R1(config)#interface serial 0/0/0

R1(config-if)#encapsulation ppp

R1(config-if)#ppp quality 80

R1(config-if)#end

Use the no ppp quality command to disable LQM.

4. How to Configure Load Balancing Across Links (MultiLinks)

Multilink PPP (also referred to as MP, MPPP, MLP, or Multilink) provides a method for spreading traffic across multiple physical WAN links while providing packet fragmentation and reassembly, proper sequencing, multivendor interoperability, and load balancing on inbound and outbound traffic.

MPPP allows packets to be fragmented and sends these fragments simultaneously over multiple point-to-point links to the same remote address. The multiple physical links come up in response to a user-defined load threshold. MPPP can measure the load on just traffic into the network, or on just traffic going out, but not on the combined load of both inbound and outbound traffic.

Use the following commands to perform load balancing across multiple links:

R1#config t

R1(config)#interface se0/0/0

R1(config-if)#encapsulation ppp

R1(config-if)#ppp multilink

R1(config-if)#end

The multilink command has no arguments. To disable PPP multilink, use the no ppp multilink command

---Original guide from orbit-computer-solutions.com

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Main Network Hardware’s Difference--- Integrated Devices, Router, Network Switch & Firewall

If you are used to working with home networking gear, you will beused to an integrated device that “does it all”. On a home network, you may have one box that is a cable/DSL modem, router, firewall, switch, and wireless access point all in one. It is amazing all the functions they can fit into one box.

If you are studying Cisco networking and learning about how businesses use these devices, you may be wondering why there is so much importance on the differences between a switch, router, firewall, and other network devices. If the home user can have all these devices combined into one, why doesn’t the business user do this as well? So, now, here we try to find out what the main differences between these network devices.

Integrated devices

Just like home devices, business devices have become more and more consolidated over time but not to the extent that the home devices have. Network administrators in a business network are more comfortable having separate devices and even like the idea. This is because network administrators like to be able to isolate problems down to a certain device and they like to be able to know the performance capabilities of every device. If you use an integrated router, switch, and firewall all into one device, troubleshooting, managing, and understanding the performance capabilities of that device gets complicated. I’m not saying that this isn’t done. You can buy a big & expensive, chassis-based, Cisco 6500 series switch and have almost all these functions on different blades of the switch. This may be fine for a larger business with a group of administrators but to a medium size business and a single network administrator, many times, this is a scary thought.

Keep in mind that for a medium or large size business, these integrated home devices won’t work because they don’t offer all the features required. The standalone routers, switches, and firewalls have many more features than these integrated devices do.

But what is the difference between these devices anyway? Let’s cover the three most popular devices. 

Router

A router is a hardware device and has the function of routing packets between networks. A router works at Layer 3 of the OSI model – the Network Layer. This is the layer that the IP protocol works at. Most routers today are IP routers that examine the source and destination IP addresses of each packet, look up the destination of the packet in the router’s IP routing table, and route that packet on its way. In the event that the destination is not listed in the routing table, the router will either send the packet to a default router (if it has one) or drop the packet. Routers are usually used to connect a local area network to a wide-area network (a LAN to a WAN) but can also be used to segment large local area networks (LAN’s).

Routers prevent broadcasts. Another way of saying this is that routers form a broadcast domain. So, if your network is being deluged by IP broadcasts, you need to subnet your network into two or more smaller networks. Those networks would be connected by a router and that router wouldn’t allow broadcast traffic to flow between subnets.

Routers use routing dynamic protocols like OSPF, RIP, or BGP to learn routes from other routers. Router can also use static routes that are entered by the administrator.

Routers replace the Ethernet MAC address of the source device with their own MAC address when they send a packet out an interface. When the response to that packet comes back, the new source of the packet is sending the response to the destination of the router. The router receives this, replaces the source address, changes the destination address to the original address, and sends the packet back to the original sender. This is a complex topic that we could spend a whole article covering so this is only meant to provide the most basic understanding of how this works.

To show the routing table on the router, use the show ip route command. Here is an example of what a routing table looks like on a router:

Switch

A switch is a hardware device that works at Layer 2 of the OSI model – data link. The data link layer is where the Ethernet protocol works.

A switch switches Ethernet frames by keeping a table of what MAC addresses have been seen on what switch port. The switch uses this table to determine where to send all future frames that it receives. In Cisco terminology, this table is called the CAM table (content addressable memory). In general, the proper term for this table is the bridge forwarding table. If a switch receives a frame with a destination MAC address that it does not have in its table, it floods that frame to all switch ports. When it receives a response, it puts that MAC address in the table so that it won’t have to flood next time.

A switch is a high-speed multiport bridge. This is why bridges are no longer needed or manufactured. Switches do what bridges did faster and cheaper. Most routers can also function as bridges.

You might be asking how a hub fits into this mix of devices. A hub is a multiport repeater. In other words, anything that comes in one port of a hub is duplicated and sent out all other ports of the hub that have devices attached. There is no intelligence to how a hub functions. A switch is a vast improvement over a hub in terms of intelligence, for many reasons. The most important of those reasons is how the bridge forwarding table works. Intelligent (smart) switches have made hubs obsolete because they can do more at the same cost of a dumb hub. For this reason, hubs are rarely used or sold any longer.

To see this bridge forwarding table (CAM table) on a Cisco switch just type: show mac-address-table

Here is an example:

Firewall

A firewall is used to protect more secure network from a less secure network. Generally, firewalls are used to protect your internal/private LAN from the Internet.

A firewall generally works at layer 3 and 4 of the OSI model. Layer 3 is the Network Layer where IP works and Layer 4 is the Transport Layer, where TCP and UDP function. Many firewalls today have advanced up the OSI layers and can even understand Layer 7 – the Application Layer.

There are a variety of different types of firewalls and we won’t go into that in this article so let’s just talk about the most popular type of firewall – a stateful packet inspection (SPI) hardware firewall. An example of a SPI hardware firewall is a Cisco PIX firewall. This is a dedicated appliance and it looks a lot like a Cisco router.

A SPI firewall is stateful because it understands the different states of the TCP (transmission control protocol) protocol. It knows what is coming and what it going and keeps track of it all. Thus, if a packet tried to come in but it wasn’t requested, the firewall knows that and drops it.

What we have learned about the Network Hardware’s Difference: Integrated Devices, Router, Network Switch & Firewall:

• Routers work at Layer 3 and route IP packets between networks.
• Routers are used to connect a LAN to a WAN (such as your small network to the Internet) but they can also be used to connect segments of a large LAN that has been subnetted into smaller segments.
• Routers route packets based on information in the IP routing table. You can see this table with the show ip route command on a Cisco router.
• Switches work at Layer 2 and switch Ethernet frames. Switches connect multiple devices on a local area network (LAN).
• Switches keep a table of Ethernet MAC addresses called a CAM Table or a Bridge forwarding table. You can see this table with the show mac-address-tablecommand on a Cisco switch.
• Firewalls work at Layers 3 and 4 but some can also work at higher layers.
• Most firewalls can keep track of the states of TCP to prevent unwanted traffic from the Internet from entering your private LAN.

---Original tip resources from petri.co.il

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Cisco refuses to deny it will sell off Linksys

Cisco router is understood to be planning to sell off its consumer router Linksys business. The company has declined to squash the rumour.

According to people familiar with the situation, the network giant is mulling over letting go of its WebEx brand, too. The moves could come as soon as next week.
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A Cisco spokesman told The Register today that the company was not willing to "comment on rumour and speculation".

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Over the past few months analysts have been wondering if cisco871 would offload Linksys among other consumer brands.

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Then cut to last month when the company closed its Flip camera business not long after Chambers said in an internal memo to Cisco staff that he wanted to "simplify the way we work and how we focus our attention and resources".