Cisco Router 826 Routers Software Configuration Guide
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1-11 Cisco 826, 827, 828, 831, 836, and 837 and Cisco SOHO 76, 77, 78, 91, 96, and 97 Routers Software Configuration Guide 78-14565-03 Chapter 1 Concepts QoS The gatekeeper maintains a registry of devices in the multimedia network. The devices register with the gatekeeper at startup and request admission to a call from the gatekeeper. The gatekeeper is an H.323 entity on the LAN that provides address translation and control access to the LAN for H.323 terminals and gateways. The gatekeeper may provide other services to the H.323 terminals and gateways, such as bandwidth management and locating gateways. Voice Dial Peers Dial peers enable outgoing calls from a particular telephony device. All of the voice technologies use dial peers to define the characteristics associated with a call leg. A call leg is a discrete segment of a call connection that lies between two points in the connection. It is important to remember that these terms are defined from the ro ut er perspective. An inbound call leg means that an incoming call comes to the router. An outbound call leg means that an outgoing call is placed from the router. Dial peers are used for both inbound and outbound call legs. For inbound call legs, a dial peer might be associated with the calling number or the voice-port number. Outbound call legs always have a dial peer associated with them. The destination pattern is used to identify the outbound dial peer. The call is associated with the outbound dial peer at setup time. There are two kinds of dial peers that need to be configured for each voice implementation: POTS—(also known as “plain old telephone service” or “basic telephone service”) dial peer associates a physical voice port with a local telephone device. The key commands in your configuration are the port and destination-pattern commands. The destination-pattern command defines the telephone number associated with the POTS dial peer. The port command associates the POTS dial peer with a specific logical dial interface, normally the voice port connecting your router to the local POTS network. Vo I P—dial peer associates a telephone number with an IP address. The key commands in your configuration are the destination-pattern command and the session target command.The destination-pattern command defines the telephone number associated with the VoIP dial peer. The session target command specifies a destination IP address for the VoIP dial peer. In addition, you can use VoIP dial peers to define characteristics such as IP precedence, additional QoS parameters, and codec. QoS This section describes Quality of Service (QoS) parameters, including the following: IP Precedence PPP Fragmentation and Interleaving CBWFQ RSVP Low Latency Queuing QoS refers to the capability of a network to provide better service to selected network traffic over various technologies, including ATM, Ethernet and IEEE 802.1 networks, and IP-routed networks that may use any or all of these underlying technologies. Primary goals of QoS include dedicated bandwidth, controlled jitter and latency (required by some real-time and interactive traffic), and improved loss characteristics. QoS technologies provide the elemental building blocks for future business applications in campus, WAN, and service provider networks.
1-12 Cisco 826, 827, 828, 831, 836, and 837 and Cisco SOHO 76, 77, 78, 91, 96, and 97 Routers Software Configuration Guide 78-14565-03 Chapter 1 Concepts QoS QoS must be configured throughout your network, not just on your router running VoIP, to improve voice network performance. Not all QoS techniques are appropriate for all network routers. Edge routers and backbone routers in your network do not necessarily perform the same operations; the QoS tasks they perform might differ as well. To configure your IP network for real-time voice traffic, you need to consider the functions of both edge and backbone routers in your network. QoS software enables complex networks to control and predictably service a variety of networked applications and traffic types. Almost any network can take advantage of QoS for optimum efficiency, whether it is a small corporate network, an Internet service provider, or an enterprise network. IP Precedence You can partition traffic in up to six classes of service using IP Precedence (two others are reserved for internal network use). The queuing technologies throughout the network can then use this signal to expedite handling. Features such as policy-based routing and committed access rate (CAR) can be used to set precedence based on extended access-list classification. This allows considerable flexibility for precedence assignment, including assignment by application or user, or by destination and source subnet, and so on. Typically this functionality is deployed as close to the edge of the network (or administrative domain) as possible, so that each subsequent network element can provide service based on the determined policy. IP Precedence can also be set in the host or network client with the signaling used optionally. IP Precedence enables service classes to be established using existing network queuing mechanisms (such as CBWFQ), with no changes to existing applications or complicated network requirements. PPP Fragmentation and Interleaving With multiclass multilink PPP interleaving, large packets can be multilink-encapsulated and fragmented into smaller packets to satisfy the delay requirements of real-time voice traffic; small real-time packets, which are not multilink encapsulated, are transmitted between fragments of the large packets. The interleaving feature also provides a special transmit queue for the smaller, delay-sensitive packets, enabling them to be transmitted earlier than other flows. Interleaving provides the delay bounds for delay-sensitive voice packets on a slow link that is used for other best-effort traffic. In general, multilink PPP with interleaving is used in conjunction with CBWFQ and RSVP or IP Precedence to ensure voice packet delivery. Use multilink PPP with interleaving and CBWFQ to define how data is managed; use Resource Reservation Protocol (RSVP) or IP precedence to give priority to voice packets. CBWFQ In general, class-based weighted fair queuing (CBWFQ) is used in conjunction with multilink PPP and interleaving and RSVP or IP Precedence to ensure voice packet delivery. CBWFQ is used with multilink PPP to define how data is managed; RSVP or IP Precedence is used to give priority to voice packets. There are two levels of queueing; ATM queues and Cisco IOS queues. CBWFQ is applied to Cisco IOS queues. A first-in-first-out (fifo) Cisco IOS queue is automatically created when a PVC is created. If you use CBWFQ to create classes and attach them to a PVC, a queue is created for each class. CBWFQ ensures that queues have sufficient bandwidth and that traffic gets predictable service. Low-volume traffic streams are preferred; high-volume traffic streams share the remaining capacity, obtaining equal or proportional bandwidth.
1-13 Cisco 826, 827, 828, 831, 836, and 837 and Cisco SOHO 76, 77, 78, 91, 96, and 97 Routers Software Configuration Guide 78-14565-03 Chapter 1 Concepts Access Lists RSVP RSVP enables routers to reserve enough bandwidth on an interface to ensure reliability and quality performance. RSVP allows end systems to request a particular QoS from the network. Real-time voice traffic requires network consistency. Without consistent QoS, real-time traffic can experience jitter, insufficient bandwidth, delay variations, or information loss. RSVP works in conjunction with current queuing mechanisms. It is up to the interface queuing mechanism (such as CBWFQ) to implement the reservation. RSVP works well on PPP, HDLC, and similar serial-line interfaces. It does not work well on multi-access LANs. RSVP can be equated to a dynamic access list for packet flows. You should configure RSVP to ensure QoS if the following conditions describe your network: Small-scale voice network implementation Links slower than 2 Mbps Links with high utilization Need for the best possible voice quality Low Latency Queuing Low latency queuing (LLQ) provides a low-latency strict priority transmit queue for real-time traffic. Strict priority queuing allows delay-sensitive data to be dequeued and sent first (before packets in other queues are dequeued), giving delay-sensitive data preferential treatment over other traffic. Access Lists With basic standard and static extended access lists, you can approximate session filtering by using the established keyword with the permit command. The established keyword filters TCP packets based on whether the ACK or RST bits are set. (Set ACK or RST bits indicate that the packet is not the first in the session and the packet therefore belongs to an established session.) This filter criterion would be part of an access list applied permanently to an interface.
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CHAPTER 2-1 Cisco 826, 827, 828, 831, 836, and 837 and Cisco SOHO 76, 77, 78, 91, 96, and 97 Routers Software Configuration Guide 78-14565-03 2 Network Scenarios This chapter includes some example network scenarios and their configurations using Cisco 827 and Cisco 827-4V routers and Cisco 831, Cisco 836, Cisco 837, Cisco SOHO 91, Cisco SOHO 96, and Cisco SOHO 97 routers. This chapter is useful if you are building a new network and want some guidance. Most of the lessons here can be applied as well to networks incorporating Cisco 826, Cisco 828, Cisco SOHO 76, Cisco SOHO 77, and/or Cisco SOHO 78 routers. NoteTo verify that a feature is compatible with your router, you can use the software advisor too. If you already have a network set up and you want to add specific features, see Chapter 3, “Basic Router Configuration” and Chapter 4, “Advanced Router Configuration.” The following sections are included in this chapter: Cisco 827 Router Network Connections, page 2-2 Cisco 831 Router Virtual Private Network Connections, page 2-3 Cisco 836 or Cisco SOHO 96 Network Connection, page 2-4 Cisco 837 Router Network Connections, page 2-5 Internet Access Scenarios, page 2-6 Configuring Dial Backup, page 2-16 Configuring the DHCP Server, page 2-39 Voice Scenario, page 2-55 Each scenario in this chapter is described with a network diagram and configuration network examples are provided as models after which you can pattern your network. They cannot, however, anticipate all of your network needs. You can choose not to use features presented in the examples or to add or substitute features that better suit your needs.
2-2 Cisco 826, 827, 828, 831, 836, and 837 and Cisco SOHO 76, 77, 78, 91, 96, and 97 Routers Software Configuration Guide 78-14565-03 Chapter 2 Network Scenarios Cisco 827 Router Network Connections Cisco 827 Router Network Connections Figure 2-1 illustrates an example network topology employing Cisco 827 routers connecting to the following: Public switched telephone network (PSTN) Corporate intranet Service provider on the Internet Service provider data center Figure 2-1 Cisco 827 Routers Network Connections 1Corporate network connecting through a Cisco 3640 voice gateway4Data and voice local exchange carrier connecting through a Cisco MGX voice gateway 2Wholesale ISP business5Small business or remote user, connecting to the network through a Cisco 827/827-4V router 3ISP POP (data center) with video conferencing MCUs and IP/TV video servers DSLAMCisco 7200 Cisco 827/827-4VCisco 3640 Cisco 6400 Cisco 6400 PSTNCisco MGXCisco 6400ISP POP 74576 ISP POP ISP POP1 2 3 4 5
2-3 Cisco 826, 827, 828, 831, 836, and 837 and Cisco SOHO 76, 77, 78, 91, 96, and 97 Routers Software Configuration Guide 78-14565-03 Chapter 2 Network Scenarios Cisco 831 Router Virtual Private Network Connections In the example, Cisco 827 routers send data or voice packets from the remote user to the service provider or corporate network through a high-speed, point-to-multi-point asymmetric digital subscriber line (ADSL) technology. Cisco 831 Router Virtual Private Network Connections Figure 2-2 shows how a Cisco 831 router can be used in a Virtual Private Network (VPN). The Cisco 831 router is linked to the ISP via a digital subscriber line (DSL) or a cable modem. Security is provided via IP security (IPSec) configuration. Figure 2-2 Cisco 831 Router Virtual Private Network 1Small business or remote user, connecting to the network through a Cisco 831 router.3Dial backup, as a failover link when primary line goes down 2Corporate network connecting through a Cisco router4Branch office network connecting through a Cisco router 82255 Cisco 831 routerxDSL or cable modem ISP PSTN Ethernet Cisco 831 routerxDSL or cable modem DES/3-DES IPSec Ethernet 1 2 3 3 4
2-4 Cisco 826, 827, 828, 831, 836, and 837 and Cisco SOHO 76, 77, 78, 91, 96, and 97 Routers Software Configuration Guide 78-14565-03 Chapter 2 Network Scenarios Cisco 836 or Cisco SOHO 96 Network Connection Cisco 836 or Cisco SOHO 96 Network Connection Figure 2-3 shows an example of a network topology employing a Cisco 836 router or a Cisco SOHO 96 router connecting to the following: ISDN Corporate intranet Service provider on the Internet Service provider data center Dial backup and remote management Figure 2-3 Cisco 836 Router Network Connections 1Corporate network connecting through a Cisco 3640 gateway4Dial backup or remote management that keeps the traffic working in case of primary line shutdown 2Wholesale ISP business5ISDN to serve as an interface for dial backup or remote management 3ISP POP (data center) with videoconferencing MCUs and IP/TV video servers6Small business or remote user, connecting to the network through a Cisco 836 router DSLAMCisco 7200 Cisco 836 Cisco 3640 Cisco 6400 Cisco 6400 ISDNCisco 7200Cisco 6400ISP POP 82797 ISP POP ISP POP1 2 3 4 4 6 5
2-5 Cisco 826, 827, 828, 831, 836, and 837 and Cisco SOHO 76, 77, 78, 91, 96, and 97 Routers Software Configuration Guide 78-14565-03 Chapter 2 Network Scenarios Cisco 837 Router Network Connections Cisco 837 Router Network Connections Figure 2-4 shows an example of a network topology employing a Cisco 837 router connecting to the following: PSTN Corporate intranet Service provider on the Internet Service provider data center Dial backup and remote management Figure 2-4 Cisco 837 Router Network Connections In the topology, Cisco 837 routers send data packets from the remote user to the service provider or corporate network through high-speed, point-to-multipoint ADSL technology. 1Corporate network connecting through a Cisco 3640 voice gateway4Dial backup or remote management that keeps the traffic working in case the primary line’s traffic shuts down 2Wholesale ISP business5PSTN to serve as an analog modem for dial backup or remote management 3ISP POP (data center) with videoconferencing MCUs and IP/TV video servers6Small business or remote user, connecting to the network through a Cisco 837 router DSLAMCisco 7200 Cisco 837 Cisco 3640 Cisco 6400 Cisco 6400 PSTNCisco 7200Cisco 6400ISP POP 82256 ISP POP ISP POP1 2 3 4 4 6 5
2-6 Cisco 826, 827, 828, 831, 836, and 837 and Cisco SOHO 76, 77, 78, 91, 96, and 97 Routers Software Configuration Guide 78-14565-03 Chapter 2 Network Scenarios Internet Access Scenarios Internet Access Scenarios Each network access scenario is described with a network diagram, configuration steps for setting up the network, and an example configuration. Before You Configure Your Internet Access Network You need to gather the following information before configuring networks based on the Internet access scenarios: Order an ADSL or G.SHDSL line from your public telephone service provider. For ADSL lines, determine that the ADSL signaling type is DMT, also called ANCII T1.413, or just DMT Issue 2. For G.SHDSL verify that the G.SHDSL line conforms to ITU standard G.991.2 and supports Annex A, for North America, or Annex B, for Europe. Gather information to set up a PPP Internet connection, including the PPP client name authentication type, and PPP password. Determine the IP routing information, including IP address, and ATM permanent virtual circuits (PVCs). These PVC parameters are typically virtual path identifier (vpi), virtual circuit identifier (vci), and traffic shaping parameters if applicable. Gather DNS server IP address and default gateways. Replacing a Bridge or Modem with a Cisco 827 Router This scenario shows a remote user connected to the Internet. You may want to use a network similar to this one if you want to set up a minimal connection to the Internet and bridge it through the Cisco 827 routers. This network replaces an Alcatel 1000 bridge or modem with a Cisco 827 or Cisco 827-4V router by using AAL5SNAP encapsulation and bridging (RFC 1483 bridge mode) on the ATM interface. Figure 2-5 shows the network topology for this scenario. Figure 2-5 Replacing a Bridge or Modem with a Cisco 827 Router 1Small business or remote user, connecting to the network through a Cisco 827 or Cisco 827-4V router2The Internet Cisco 827/827-4VDSLAM Cisco 6400DHCP74577Cisco 6400 12