User guide

Release Notes for Cisco 2500 Series for Cisco IOS Release 12.0 T 27
New Software Features in Release 12.0(1)T
• Denial-of-service detection and prevention
• Real-time alerts and audit trails
The Cisco IOS Firewall feature set adds advanced filtering capabilities to existing security
functionality in Cisco routers. Some existing Cisco IOS security features include packet filtering via
access control lists (ACLs), Network Address Translation (NAT), network-layer encryption, and
TACACS+ authentication.
ISDN MIB RFC2127
The new Integrated Services Digital Network (ISDN) Management Information Base (MIB)
RFC2127 has been designed to provide useful information in accordance with the IETF’s new
standard for the management of ISDN interfaces. It controls all aspects of ISDN interfaces.
RFC2127 provides information on the physical Basic Rate Interfaces (BRIs), control and statistical
information for B (bearer) and D (signaling) channels, terminal endpoints, and directory numbers.
IOS STP Enhancements
IOS Spanning Tree Protocol enhancements broaden the original IOS STP implementation with
increased port identification capability, improved path cost determination, and support for a new
VLAN bridge spanning-tree protocol.
Layer Two Tunneling Protocol (L2TP)
Layer Two Tunneling Protocol (L2TP) is an emerging Internet Engineering Task Force (IETF)
standard that combines the best features of two existing tunneling protocols: Cisco's Layer Two
Forwarding (L2F) and Microsoft's Point-to-Point Tunneling Protocol (PPTP). L2TP is an extension
to the Point-to-Point Protocol (PPP), which is an important component for Access Virtual Private
Networks (VPNs). Access VPNs allow mobile users to connect to their corporate intranets or
extranets, thus improving flexibility and reducing costs.
Traditional dial-up networking services only supported registered IP address, which limited the
types of applications that could be implemented over Virtual Private Networks (VPNs). L2TP
supports multiple protocols and unregistered and privately administered IP addresses over the
Internet. This allows the existing access infrastructure, such as the Internet, modems, access servers,
and ISDN terminal adaptors (TAs), to be used.
L2TP can be initiated wherever PPTP or L2F is currently deployed and can be operated as a client
initiated tunnel, such as PPTP, or a network access server (NAS) initiated tunnel, such as L2F.
PPP Over Frame Relay
The PPP over Frame Relay feature allows a router to establish end-to-end Point-to-Point Protocol
(PPP) sessions over Frame Relay. IP datagrams are transported over the PPP link using RFC 1973
compliant Frame Relay framing. This feature is useful for remote users running PPP to access their
Frame Relay corporate networks.
PPP over Frame Relay provides the following benefits:
• Allows end-to-end PPP sessions over Frame Relay.
• Supports the 90i IDSL Channel Unit that supports both Frame Relay and Point-to-Point Protocol
(PPP) on an ISDN DSL.