Name 5 components of PPP.
- contains header and trailer
- supports synchronous and async links
- Protocol Type field in header allows multiple L3 protocols
- Built in authentication tools
- Control protocols for each higher layer protocol
What are the 2 main categories of control protocols?
- Link Control Protocols (LCP
- Network Control Protocols (NCP)
How many LCPs are used per link?
1
How many NCPs are used per link?
One for each L3 protocol
What are 4 functions that LCP performs?
- Looped link detection
- Error detection
- Multilink Support
- Authentication
How does the PAP process work?
Initialized by router wanting to be authenticated by sending username and password in clear text
How does CHAP work?
- Authenticating router sends CHALLENGE with shared Random Number
- Router who wants to be authenticated creates and sends HASH based on username, password and shared Random Number
- Authenticating router compares received Hash with Hash it created. If a match then replies with PASS.
What happens if authentication fails?
PPP leaves the interface in an Up/Down state
What is CHAP’s one-way hash algorithm called?
MD5
On the authenticating router what input goes into the HASH
- Username
- Password
- Shared random number
What command takes an HDLC link and changes it to PPP?
encapsulation ppp
Do IP addresses need to be configured for PPP to work?
No
What are the steps for configuring PPP with CHAP?
- username (remote_router_hostname) password mypass
- int s0/0
- encapsulation ppp
- ppp authentication chap
What are 2 ways to tell if CHAP authentication has failed?
- interface in up/down state
- show ppp all
What are the steps for configuring PPP with PAP
- username (remote_router_sent-username) password (remote_router_sent-username_password)
- int s0/0
- encapsulation ppp
- ppp authentication pap
- ppp pap sent-username (local_router_hostname) password (local_router_password)
What are 2 ways to tell if PAP authentication failed?
- interface in up/down state
- show ppp all
What is the difference between how CHAP passwords are configured vs. PAP passwords?
- CHAP requires password to match on both ends
- finds correct username/password combination to send based on the username match
- PAP relies on the sent-username interface command for username and password.
What is the default load balancing method used on 2 equal-metric serial links?
Per destination
How does MLPPP do load balancing?
It fragments the packet with each fragment having its own PPP header/trailer.
What are the commands to configure a serial interface for MLPPP?
- int s0/0
- no ip address
- encap ppp
- ppp multilink
- ppp multilink group 1
- authentication (if configured)
What are the commands to configure a multilink interface for MLPPP?
- int mu1
- ip address 1.1.1.1 255.255.255.0
- encap ppp
- ppp multilink
- ppp multilink group 1
When configuring MLPPP, which parameters must match on both ends of the link?
- the multilink interface number (mu1)
- the multilink group number
For MLPPP, which 3 commands are the same on both physical interfaces and multilink interface?
- encap ppp
- ppp multilink
- ppp multilink group 1
What 2 show commands verify multilink is working?
- show interfaces mu1
- show ppp multilink
