AIS AI2524 user manual Precedence Rules

Chapter 11: AI2524 Sync PPP Configuration Steps

zDefault IP address. The peer default ip address com- mand and the member peer default ip address com- mand can be used to define default peer IP addresses.

zTACACS+ assigned IP address. During the authorization phase of IPCP address negotiation, TACACS+ can return an IP address that can be used by the user being authenticated on a dial-up interface. This address overrides any default IP address and prevents pooling from taking place.

zDHCP retrieved IP address. If configured, the routers acts as a proxy client for the dial-up user and retrieves an IP address from a DHCP server. That address is returned to the DHCP server when the timer expires or when the interface goes down.

zLocal address pool. The local address pool contains a set of con- tiguous IP addresses (a maximum of 256 addresses) stored in two queues. The free queue contains addresses available to be as- signed. The used queue contains addresses that are in use. Ad- dresses are stored in the free queue in First-In First-Out (FIFO order to minimize the chance the address will be reused and to al- low a peer to reconnect using the same address that it used in the last connection. If the address is available, it is assigned; if not, an- other address from the free queue is assigned.

The pool configured for the interface is used, unless TACACS+ returns a pool name as part of authentication, authorization, and accounting (AAA). If no pool is associated with a given interface, the global pool named default is used.

Precedence Rules

These precedence rules of peer IP address support determine which address is used. Precedence is listed from most likely to least likely:

1.AAA/TACACS+ provided address or addresses from the pool named by AAA/TACACS+

2.An address from a local IP address pool or DHCP (typically not allocated unless no other address exists)

3.Dialer map lookup address (not done unless no other address ex ists)

August 1997	Page 11-9
2524UM