Protocol-dependent module
Encyclopedia
Protocol-dependent modules (PDMs) are used by the routing protocol
EIGRP to make decisions about adding routes learned from other sources; for example other routers or routing protocols to the routing table
. The PDM is also capable of carrying information from the routing table to the topology table
. EIGRP offers support for various routed protocols (e.g. Internet Protocol Version 6 (IPv6)
, IP
, IPX, AppleTalk
), and has added support for Service Routing (SAF) PDMs. The only other routing protocol that comes supports multiple network layer protocol is Intermediate System-to-Intermediate System (IS-IS)
Routing protocol
A routing protocol is a protocol that specifies how routers communicate with each other, disseminating information that enables them to select routes between any two nodes on a computer network, the choice of the route being done by routing algorithms. Each router has a priori knowledge only of...
EIGRP to make decisions about adding routes learned from other sources; for example other routers or routing protocols to the routing table
Routing table
In computer networking a routing table, or Routing Information Base , is a data table stored in a router or a networked computer that lists the routes to particular network destinations, and in some cases, metrics associated with those routes. The routing table contains information about the...
. The PDM is also capable of carrying information from the routing table to the topology table
Topology table
A topology table is used by routers that route traffic in a network. It consists of all routing tables inside the Autonomous System where the router is positioned. Each router using the routing protocol EIGRP then maintains a topology table for each configured network protocol — all routes learned,...
. EIGRP offers support for various routed protocols (e.g. Internet Protocol Version 6 (IPv6)
IPv6
Internet Protocol version 6 is a version of the Internet Protocol . It is designed to succeed the Internet Protocol version 4...
, IP
Internet Protocol
The Internet Protocol is the principal communications protocol used for relaying datagrams across an internetwork using the Internet Protocol Suite...
, IPX, AppleTalk
AppleTalk
AppleTalk is a proprietary suite of protocols developed by Apple Inc. for networking computers. It was included in the original Macintosh released in 1984, but is now unsupported as of the release of Mac OS X v10.6 in 2009 in favor of TCP/IP networking...
), and has added support for Service Routing (SAF) PDMs. The only other routing protocol that comes supports multiple network layer protocol is Intermediate System-to-Intermediate System (IS-IS)
"In theory, EIGRP can add PDMs to easily adapt to new or revised routed protocols such as IPv6IPv6Internet Protocol version 6 is a version of the Internet Protocol . It is designed to succeed the Internet Protocol version 4...
. Each PDM is responsible for all functions related to its specific routed protocol. The IP-EIGRP module is responsible for the following functions:
- Send and receive EIGRP packets that bear IP data.
- Notify DUAL (Diffusing Update Algorithm
Diffusing update algorithmDUAL, the Diffusing Update ALgorithm, is the algorithm used by Cisco's EIGRP routing protocol to ensure that a given route is recalculated globally whenever it might cause a routing loop. It was developed by J.J. Garcia-Luna-Aceves at SRI International. According to Cisco, the full name of the...
) of new IP routing information that is received.- Maintain the results of DUAL routing decisions in the IP routing table.
- Redistribute routing information that was learned by other IP-capable routing protocols."