IPCP Negotiation with Optional Peer IP Address Overview

During normal operation for an IPCP negotiation, if the client does not request a specific IP address, the server sends an IP address obtained from RADIUS or from the local address pool.

If the client seeks a specific IP address, on receiving a NAK from the server, it sends a confReq message without specifying the IP address option. In this case, even though the server sends an IPCP confAck message , the server terminates the client because the server requires an IP address from the client.

You can use the ppp peer-ip-address-optional command in Global Configuration mode to specify that the peer IP address is optional. By default, this command is disabled. This feature also supports high availability (HA) and unified in-service software upgrade (Unified ISSU).

Note: Even though the ppp peer-ip-address-optional command is configured, on receiving a NAK from the server, if the client sends an IPCP confReq message with specific IP address, IPCP is terminated after a maximum of five attempts.

When the IPCP negotiation succeeds by configuring the ppp peer-ip-address-optional command, the server does not have the client IP address. An IP address from RADIUS or from the local pool is allocated to the client and the route towards this is added on the server even though the client is not assigned with this address. If you want the server to have the route to the client-requested IP address, use the framed-route RADIUS attribute or configure statics routes. The client adds or configures static routes towards the server for proper forwarding.