Cayman Systems 2E-W, User Manual

Page: 148 / 170

How Your Cayman 2E-W Works Cayman 2E-W User’s Guide
C-10
November 2000
expiration of an activity time or intervention by a network
administrator, occurs.
When a peer no longer needs a link, it sends a Terminate-Request
packet to the remote peer and closes any open NCP sessions. When
a peer sending a Terminate-Request receives a Terminate-Ack packet
(or after a specified number of unacknowledged Terminate-Request
packets are sent), it signals the physical layer to disconnect to
enforce the termination of the link.
PPP and Routing
Tables
Your Cayman 2E-W maintains a routing table for its IP routing
service. The routing table identifies the networks a router can reach,
the interface and gateway through which the router must forward a
packet to reach its destination, and the number of routers (metric or
hop count) through which a packet must travel to reach a remote
network. When the router receives a packet, it consults its routing
table to decide where to send the packet.
Static and Dynamic Routes
Routes to other networks can be entered and maintained manually
(static routes) or acquired from other routers interactively (dynamic
routes):
Static routes identify pathways to destination networks that are
stable over time or to networks that must always be available,
even if a link is not currently open. These static routes let each
router recognize how to reach the other, even if one router
hasn't heard from the other recently. Static routes are usually
required for a PPP link to be established “on demand,” since,
without it, the router does not know which interface to route a
packet over to reach the remote network.
Dynamic routes identify pathways to destination networks that
may change over time. Dynamic routes are created and
configured when routers broadcast RIP (Routing Information
Protocol) packets advertising the networks they can reach and
the distance (number of routers) to each network.