Configuring PPP negotiation
PPP negotiation includes the following parameters:
Negotiation timeout time.
IP address negotiation.
IP segment match.
DNS server IP address negotiation.
ACCM negotiation.
ACFC negotiation.
PFC negotiation.
Configuring the PPP negotiation timeout time
The device starts the PPP negotiation timeout timer after sending a packet. If no response is received before the timer expires, the device sends the packet again.
If two ends of a PPP link vary greatly in the LCP negotiation packet processing rate, configure the LCP negotiation delay timer on the end with a higher processing rate. The LCP negotiation delay timer prevents frequent LCP negotiation packet retransmissions. After the physical layer comes up, PPP starts LCP negotiation when the delay timer expires. If PPP receives LCP negotiation packets before the delay timer expires, it starts LCP negotiation immediately.
To configure the PPP negotiation timeout time:
Step | Command | Remarks |
|---|---|---|
1. Enter system view. | system-view | N/A |
2. Enter interface view. | interface interface-type interface-number | N/A |
3. Configure the negotiation timeout time. | ppp timer negotiate seconds | The default setting is 3 seconds. |
4. (Optional.) Configure the LCP negotiation delay timer. | ppp lcp delay milliseconds | By default, PPP starts LCP negotiation immediately after the physical layer is up. |
Configuring IP address negotiation
To configure the device as the client:
Step | Command | Remarks |
|---|---|---|
1. Enter system view. | system-view | N/A |
2. Enter interface view. | interface interface-type interface-number | N/A |
3. Enable IP address negotiation. | ip address ppp-negotiate | By default, IP address negotiation is not enabled. This command is mutually exclusive with the ip address command. For more information about the ip address command, see Layer 3—IP Services Command Reference. |
Configure the server to assign an IP address to a client by using the following methods:
Method 1: Specify an IP address for the client on the server interface.
Method 2: Specify a PPP or DHCP address pool on the server interface.
Method 3: Associate a PPP or DHCP address pool with an ISP domain.
For clients requiring no authentication, you can use either method 1 or method 2, but not both.
For clients requiring authentication, you can use one or more of the three methods, but cannot use method 1 and method 2 at the same time. When multiple methods are configured, method 3 takes precedence over method 1 or method 2.
PPP supports IP address assignment from a PPP or DHCP address pool. If you use a pool name that identifies both a PPP address pool and a DHCP address pool, the system uses the PPP address pool.
To configure the device as the server (Method 1):
Step | Command | Remarks |
|---|---|---|
1. Enter system view. | system-view | N/A |
2. Enter interface view. | interface interface-type interface-number | N/A |
3. Configure the interface to assign an IP address to the peer. | remote address ip-address | By default, an interface does not assign an IP address to the peer. |
4. Configure an IP address for the interface. | ip address ip-address | By default, no IP address is configured on an interface. |
To configure the device as the server (Method 2: Specify a PPP address pool):
Step | Command | Remarks |
|---|---|---|
1. Enter system view. | system-view | N/A |
2. Configure a PPP address pool. | ip pool pool-name start-ip-address [ end-ip-address ] [ group group-name ] | By default, no PPP address pool is configured. |
3. (Optional.) Configure a gateway address for the PPP address pool. | ip pool pool-name gateway ip-address [ vpn-instance vpn-instance-name ] | By default, the PPP address pool is not configured with a gateway address. |
4. (Optional.) Configure a PPP address pool route. | ppp ip-pool route ip-address { mask-length | mask } [ vpn-instance vpn-instance-name ] | By default, no PPP address pool route exists. The destination network of the PPP address pool route must include the PPP address pool. |
5. Enter interface view. | interface interface-type interface-number | N/A |
6. Configure the interface to assign an IP address from the configured PPP address pool to the peer. | remote address pool pool-name | By default, an interface does not assign an IP address to the peer. |
7. Configure an IP address for the interface. | ip address ip-address | By default, no IP address is configured on an interface. This command is optional when the PPP address pool has been configured with a gateway address. |
To configure the device as the server (Method 2: Specify a DHCP address pool):
Step | Command | Remarks |
|---|---|---|
1. Enter system view. | system-view | N/A |
2. Configure DHCP. |
| For information about configuring DHCP, see Layer 3 IP Services Configuration Guide. |
3. Enter interface view. | interface interface-type interface-number | N/A |
4. Configure the interface to assign an IP address from the configured DHCP address pool to the peer. | remote address pool pool-name | By default, an interface does not assign an IP address to the peer. |
5. Configure an IP address for the interface. | ip address ip-address | By default, no IP address is configured on an interface. |
To configure the device as the server (Method 3: Associate a PPP address pool with an ISP domain):
Step | Command | Remarks |
|---|---|---|
1. Enter system view. | system-view | N/A |
2. Configure a PPP address pool. | ip pool pool-name start-ip-address [ end-ip-address ] [ group group-name ] | By default, no PPP address pool is configured. |
3. (Optional.) Configure a gateway address for the PPP address pool. | ip pool pool-name gateway ip-address [ vpn-instance vpn-instance-name ] | By default, the PPP address pool is not configured with a gateway address. |
4. (Optional.) Configure a PPP address pool route. | ppp ip-pool route ip-address { mask-length | mask } [ vpn-instance vpn-instance-name ] | By default, no PPP address pool route exists. The destination network of the PPP address pool route must include the PPP address pool. |
5. Enter ISP domain view. | domain isp-name | N/A |
6. Associate the ISP domain with the configured PPP address pool for address assignment. | authorization-attribute ip-pool pool-name | By default, no PPP address pool is associated. For more information about this command, see Security Command Reference. |
7. Return to system view. | quit | N/A |
8. Enter interface view. | interface interface-type interface-number | N/A |
9. Configure an IP address for the interface. | ip address ip-address | By default, no IP address is configured on an interface. This command is optional when the PPP address pool is configured with a gateway address. |
To configure the device as the server (Method 3: Associate a DHCP address pool with an ISP domain):
Step | Command | Remarks |
|---|---|---|
1. Enter system view. | system-view | N/A |
2. Configure DHCP. |
| For information about configuring DHCP, see Layer 3 IP Services Configuration Guide. |
3. Enter ISP domain view. | domain isp-name | N/A |
4. Associate the ISP domain with the configured DHCP address pool for address assignment. | authorization-attribute ip-pool pool-name | By default, no DHCP address pool is associated. For more information about this command, see Security Command Reference. |
5. Return to system view. | quit | N/A |
6. Enter interface view. | interface interface-type interface-number | N/A |
7. Configure an IP address for the interface. | ip address ip-address | By default, no IP address is configured on an interface. |
Enabling IP segment match
This feature enables the local interface to check whether its IP address and the IP address of the remote interface are in the same network segment. If they are not, IPCP negotiation fails.
To enable IP segment match:
Step | Command | Remarks |
|---|---|---|
1. Enter system view. | system-view | N/A |
2. Enter interface view. | interface interface-type interface-number | N/A |
3. Enable IP segment match. | ppp ipcp remote-address match | By default, this feature is disabled. |
Configuring DNS server IP address negotiation
Configure DNS server settings depending on the role of your device in PPP negotiation.
Configuring the local end as the client
During PPP negotiation, the server will assign a DNS server IP address only for a client configured with the ppp ipcp dns request command. For some special devices to forcibly assign DNS server IP addresses to clients that do not initiate requests, configure the ppp ipcp dns admit-any command on these devices.
To configure the local end as the client:
Step | Command | Remarks |
|---|---|---|
1. Enter system view. | system-view | N/A |
2. Enter interface view. | interface interface-type interface-number | N/A |
3. Enable the device to request the peer for a DNS server IP address. | ppp ipcp dns request | By default, a client does not request its peer for a DNS server IP address. |
4. Configure the device to accept the DNS server IP addresses assigned by the peer even though it does not request the peer for the DNS server IP addresses. | ppp ipcp dns admit-any | By default, a device does not accept the DNS server IP addresses assigned by the peer if it does not request the peer for the DNS server IP addresses. This command is not necessary if the ppp ipcp dns request command is configured. |
Configuring the local end as the server
Step | Command | Remarks |
|---|---|---|
1. Enter system view. | system-view | N/A |
2. Enter interface view. | interface interface-type interface-number | N/A |
3. Specify the primary and secondary DNS server IP addresses to be allocated to the peer in PPP negotiation. | ppp ipcp dns primary-dns-address [ secondary-dns-address ] | By default, a device does not allocate DNS server IP addresses to its peer if the peer does not request them. |
Configuring ACCM negotiation
PPP uses the escape mechanism on asynchronous links to avoid treating payload characters as control characters. The escape mechanism converts all one-byte asynchronous control characters into two-byte characters. This mechanism increases the size of asynchronous control characters and reduces the payload size.
The ACCM configuration option provides a method to negotiate with the peer of the local control characters, which must be converted on asynchronous links. The ACCM field contains 32 bits numbered 1 to 32 from left to right. Each bit corresponds to an asynchronous control character numbered the same. If the value of a bit is 0, the system does not convert the corresponding asynchronous control character. If the value of a bit is 1, the system converts the corresponding asynchronous control character by prefacing it with a backslash (\). For example, if the value of the bit numbered 19 is 0, the asynchronous control character numbered 19 (DC3, Control-S) will be sent without being converted.
ACCM negotiation is implemented at the LCP negotiation stage. After ACCM negotiation is completed, the peer converts asynchronous control characters according to the Async Control Character Mappings when sending packets.
By default, the ACCM field takes the value of 0x000A0000. To increase the payload size on low-rate links, set the ACCM field to 0x0 so the system does not convert asynchronous control characters.
To configure ACCM negotiation:
Step | Command | Remarks |
|---|---|---|
1. Enter system view. | system-view | N/A |
2. Enter interface view. | interface interface-type interface-number | N/A |
3. Configure the ACCM value. | ppp accm hex-number | By default, the ACCM value is 0x000A0000. The ACCM negotiation option applies only to asynchronous links. |
Configuring ACFC negotiation
PPP can compress the address and control fields of PPP packets to increase the payload size.
ACFC negotiation notifies the peer that the local end can receive packets carrying compressed address and control fields.
ACFC negotiation is implemented at the LCP negotiation stage. After the ACFC negotiation succeeds, PPP does not include the address and control fields in non-LCP packets. To ensure successful LCP negotiation, PPP does not apply the compression to LCP packets.
As a best practice, use the ACFC configuration option on low-speed links.
To configure the local end to send ACFC requests:
Step | Command | Remarks |
|---|---|---|
1. Enter system view. | system-view | N/A |
2. Enter interface view. | interface interface-type interface-number | N/A |
3. Configure the local end to send ACFC requests by including the ACFC option in outbound LCP negotiation requests. | ppp acfc local request | By default, the local end does not include the ACFC option in outbound LCP negotiation requests. |
To configure the local end to reject ACFC requests received from the peer:
Step | Command | Remarks |
|---|---|---|
1. Enter system view. | system-view | N/A |
2. Enter interface view. | interface interface-type interface-number | N/A |
3. Configure the local end to reject ACFC requests received from the peer. | ppp acfc remote-reject | By default, the local end accepts the ACFC requests from the remote peer, and performs ACFC on frames sent to the peer. |
Configuring PFC negotiation
PPP can compress the protocol field of PPP packets from 2 bytes to 1 byte to increase the payload size.
PFC negotiation notifies the peer that the local end can receive packets with a single-byte protocol field.
PFC negotiation is implemented at the LCP negotiation stage. After PFC negotiation is completed, the device compresses the protocol field of sent non-LCP packets. If the first eight bits of the protocol field are all zeros, the device does not add those bits into the packet. To ensure successful LCP negotiation, PPP does not apply the compression to LCP packets.
As a best practice, use this configuration option on low-speed links.
To configure the local end to send PFC requests:
Step | Command | Remarks |
|---|---|---|
1. Enter system view. | system-view | N/A |
2. Enter interface view. | interface interface-type interface-number | N/A |
3. Configure the local end to send PFC requests by including the PFC option in outbound LCP negotiation requests. | ppp pfc local request | By default, the local end does not include the PFC option in outbound LCP negotiation requests. |
To configure the local end to reject PFC requests received from the peer:
Step | Command | Remarks |
|---|---|---|
1. Enter system view. | system-view | N/A |
2. Enter interface view. | interface interface-type interface-number | N/A |
3. Configure the local end to reject PFC requests received from the peer. | ppp pfc remote-reject | By default, the device accepts PFC requests received from the peer, and performs PFC on frames sent to the peer. |