User guide

Release Notes for Cisco 2500 Series for Cisco IOS Release 12.0 T 15

New Software Features in Release 12.0(3)T

Although the Dynamic Multiple Encapsulations feature enhances large scale dial-in functionality,

the feature also works well in smaller scale dial-in situations and for modem calls.

New Software Features in Release 12.0(3)T

The following new software enhancements are supported by the Cisco 2500 series in

Release 12.0(3)T.

Annex-G (X.25 over Frame Relay)

Annex G (X.25 over Frame Relay) facilitates the migration from an X.25 backbone to a Frame Relay

backbone by permitting encapsulation of CCITT X.25/X.75 trafﬁc within a Frame Relay

connection. Annex G has developed to accommodate the many Cisco customers in Europe, where

X.25 still is a popular protocol. With Annex G, the process of transporting X.25 over Frame Relay

has been simpliﬁed, by allowing direct X.25 encapsulation over a Frame Relay network.

This simple process is largely achieved using X.25 proﬁles (similar to dialer proﬁles), which were

created to streamline the conﬁguration of X.25 on a per DLCI basis. X.25 proﬁles can contain any

existing X.25 command and, once created and named, can be simultaneously associated with more

than one Annex G DLCI connection, just using the proﬁle name.

CDP Additions for Cisco IOS

The Cisco Discovery Protocol (CDP) is a media-independent device discovery protocol that runs on

all cisco manufactured equipment, including routers, bridges, access servers, and switches. Each

device sends periodic messages to a multicast address. Each device listens to the periodic messages

sent by others in order to learn about neighboring devices and determine when their interfaces to the

media go up or down. With CDP, network management applications can learn the device type and

the SNMP agent address of neighboring devices. This process enables applications to send SNMP

queries to neighboring devices.

CDP runs on all media that support Subnetwork Access Protocol (SNAP), including local-area

network (LAN), Frame Relay, and Asynchronous Transfer Mode (ATM) media. CDP runs over the

data link layer only. Therefore, two systems that support different network-layer protocols can learn

about each other.

Each device conﬁgured for CDP sends periodic messages to a multicast address. Each device

advertises at least one address at which it can receive SNMP messages. The advertisements also

contain time-to-live, or holdtime, information, which indicates the time a receiving device should

hold CDP information before discarding it.

Additions for Cisco Discovery Protocol (CDP) include the following:

• new SYSLOG output for instances of mismatching native VLAN IDs (IEEE 802.1Q) on

connecting ports and port duplex state values on connecting devices.

• cdp advertise-v2 command and new output from show cdp commands

The beneﬁts include, transparent support of X.25 encapsulation over the Frame Relay network;

direct X.25 conﬁgurations on a per DLCI basis; multiple Annex G DLCIs can use the same X.25

proﬁle; multiple logical X.25 SVCs per Annex G link, and the fact that Cisco routers already contain

the functionality necessary to perform the framing and frame removal required by Annex G.