PPP Questions

Question 1

Question 2

Question 3

Explanation

Both routers must use the same password for CHAP to authentication.

Question 4

Explanation

Point-to-point leased line is the most expensive interconnection between two ends as the line is dedicated to a single user, the user should still pay for all available bandwidth, including those unused. -> A is not correct.

With the cost of point-to-point leased line, the full-mesh capability is only achieved when your company has very very strong budget to pay all the bills. To create a full-mesh topology for n sites, we need n*(n-1)/2 leased line connections. For example if we have 6 sites then we need 6*5/2 = 15 leased line connections -> It is nearly impossible for a normal company to achieve full-mesh topology -> B is not correct.

Flexibility is not an advantage of leased line connection -> C is not correct.

Point-to-point leased line simplifies the configuration as the circuit is available on a permanent basis and does not require a connection to be set up before traffic is passed. It does not require to define a permanent virtual circuit (PVC) in the configuration either -> D is correct.

Question 5

Explanation

Suppose R1 has two Serial interfaces which are directly connected to R2. This is how to configure multilink on R1:

R1(config-if)# interface Serial 0/0
R1(config-if)# encapsulation ppp
R1(config-if)# ppp multilink
R1(config-if)# ppp multilink group 1
R1(config-if)# no shutdown

R1(config-if)# interface Serial 0/1
R1(config-if)# encapsulation ppp
R1(config-if)# ppp multilink
R1(config-if)# ppp multilink group 1
R1(config-if)# no shutdown

R1(config)# interface multilink 1
R1(config-if)# ip address 192.168.42.1 255.255.255.252
R1(config-if)# ppp multilink
R1(config-if)# ppp multilink group 1

Therefore we must configure IP address under multilink interface, not physical member interfaces.

Question 6

Explanation

The Multilink PPP feature provides load balancing functionality over multiple WAN links while providing multivendor interoperability and support for packet fragmentation, proper sequencing, and load calculation on both inbound and outbound traffic.

Multilink PPP combines multiple physical links into a logical bundle called a Multilink PPP bundle. A Multilink PPP bundle is a single, virtual interface that connects to the peer system. Having a single interface (Multilink PPP bundle interface) provides a single point to apply hierarchical queueing, shaping, and policing to traffic flows. Individual links in a bundle do not perform any hierarchical queueing. None of the links have any knowledge about the traffic on parallel links.

Reference: http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/wan_mlp/configuration/xe-3s/wan-mlp-xe-3s-book/wan_cfg_mlppp_conn_xe.html

MLPPP supports two authentication protocols: Password Authentication protocol (PAP) and Challenge-Handshake Authentication Protocol (CHAP)

Question 7

Question 8

Explanation

The command “ppp authentication chap pap” command indicates the CHAP authentication is used first. If it fails or is rejected by other side then uses PAP instead. If you want to use PAP first (then CHAP) you can use the “ppp authentication pap chap” command.