4000 Router Series Layer 2 - WAN Configuration Guide

becomes ready to carry negotiated network-layer protocol packets. If the NCP negotiation fails,

NCP reports a Down event and enters the Link Termination phase.

If the interface is configured with an IP address, the IPCP negotiation is performed. IPCP

configuration options include IP addresses and DNS server IP addresses. After the IPCP

negotiation succeeds, the link can carry IP packets.

5. After the NCP negotiation is performed, the PPP link remains active until explicit LCP or NCP

frames close the link, or until some external events take place (for example, the intervention of a

user).

For more information about PPP, see RFC 1661.

PPP authentication

PPP provides authentication methods, which makes it viable to implement AAA on PPP links. Combining

PPP with AAA can perform authentication and accounting for clients.

PPP supports the following authentication methods:

• PAP—PAP is a two-way handshake authentication protocol that uses the username and password.

PAP sends username/password pairs in plain text over the network. If authentication packets are

intercepted in transit, network security might be threatened. For this reason, it is suitable only for

low-security environments.

• CHAP—CHAP is a three-way handshake authentication protocol.

CHAP transmits usernames but not passwords over the network. Therefore, it is more secure than

PAP. The authenticator may or may not be configured with a username. HP recommends that you

configure a username for the authenticator, which makes it easier for the peer to verify the identity

of the authenticator.

MP overview

Multilink PPP (MP) allows you to bind multiple PPP links into one MP bundle for increasing bandwidth.

After receiving a packet that is larger than the minimum packet size for fragmentation, MP fragments the

packet and distributes the fragments across multiple PPP links to the peer. After the peer receives these

fragments, it reassembles them into one packet and passes the packet to the network layer.

In addition to increasing bandwidth, MP also provides link-layer load sharing, which can implement

backup. MP fragmentation can reduce transmission delay, especially on low-speed links.

MP is available to all physical or virtual interfaces with PPP encapsulation enabled, including serial,

ISDN BRI/PRI, and PPPoX (PPPoE, PPPoA, or PPPoFR) interfaces. In MP configuration, however, it is

preferred that an MP bundle include only one type of interface.

Configuring PPP

PPP configuration task list

Tasks at a

lance

(Required.) Enabling PPP encapsulation on an interface