Configuring DVSR

Contents

1Overview

2

Configuration and Operations Tasks
2.1Configuring a DVSR Profile
2.2Performing DVSR Operations

3

Configuration Examples
3.1Basic DVSR
3.2DVSR in Anycast Application
3.3DVSR in Customer Multihoming Application
Copyright

© Ericsson AB 2009–2010. All rights reserved. No part of this document may be reproduced in any form without the written permission of the copyright owner.

Disclaimer

The contents of this document are subject to revision without notice due to continued progress in methodology, design and manufacturing. Ericsson shall have no liability for any error or damage of any kind resulting from the use of this document.

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1   Overview

This document provides an overview of dynamically verified static routing (DVSR), describes the tasks and commands used to configure, monitor, troubleshoot, and administer DVSR features through the SmartEdge® router, and provides DVSR configuration examples.

DVSR is a semidynamic and semistatic routing protocol used mainly for making edge routing decisions.

The SmartEdge router supports DVSR as a unique edge routing feature in addition to static routing and regular Interior Gateway Protocols (IGPs), such as Intermediate System-to-Intermediate System (IS-IS), Open Shortest Path First (OSPF), and Routing Information Protocol (RIP). DVSR is similar to normal static routing. The main difference is that the DVSR’s next hop, or some other relevant host IP address, is dynamically verified by this protocol before the prefix can be injected into the local routing table. In many ISP networks, using static routing without proper next-hop checks results in blackholing of network traffic.

Static routes are often used on edge routers; however, with this additional dynamic host address verification, it can be safely used in some cases where static routing is not considered to be appropriate.

The DVSR routes can be redistributed into Border Gateway Protocol (BGP) or IGPs. A number of mechanisms can be used to redistribute specific DVSR routes; for example:

There are many applications where DVSR can be applied, including the following applications:

2   Configuration and Operations Tasks

To configure DVSR, perform the tasks described in the sections that follow.

2.1   Configuring a DVSR Profile

To configure a DVSR profile, perform the tasks described in Table 1. Enter all commands in DVSR profile configuration mode, unless otherwise noted.

Note:  
In this section, the command syntax in the task tables displays only the root command.

Table 1    Configure a DVSR Profile

Task

Root Command

Notes

Create a DVSR profile and enter DVSR profile configuration mode.

dvsr-profile

Enter this command in context configuration mode.


If no DVSR parameters are set, the profile uses default values for the DVSR parameters. All DVSR routes must reference an existing DVSR profile.

Configure the distance value for a DVSR profile.

distance (DVSR profiles)

You can also define the distance value when configuring a DVSR route. In that case, the defined DVSR route distance overwrites the distance specified in the DVSR profile.

Configure the packet source IP address value for the DVSR profile.

source-address

Configure the route tag value for the DVSR profile.

tag

You can also define the route tag value when configuring a DVSR route. In that case, the specified DVSR route tag value overwrites the value in the DVSR profile.

Configure the TTL value for the DVSR profile.

ttl

Configure verify-set values for a DVSR profile.

verify-set

2.2   Performing DVSR Operations

To manage DVSR functions, perform the appropriate tasks described in Table 2. Enter the show command (in any mode); enter the clear and debug commands in exec mode.

Table 2    DVSR Operations Tasks

Task

Root Command

Clear all DVSR statistics in the DVSR summary table.

clear dvsr statistics

Enable the generation of DVSR debug messages.

debug static dvsr

Display information about all DVSR routes.

show dvsr

3   Configuration Examples

The sections that follow provide DVSR configuration examples.

3.1   Basic DVSR

To enable DVSR, or to announce DVSR routes, you must first define a DVSR profile. DVSR routes may have different requirement, thus more than one DVSR profile can be configured. Optionally, each DVSR route can specify parameters to overwrite profile definitions.

The following example shows one DVSR profile, and one DVSR route, using all default parameters. The DVSR profile abc-web is configured with a prefix of 10.10.0.0/16, and with a next hop of 10.1.1.1. The DVSR verify host is the next hop of the prefix, which is 10.1.1.1. As long as the 10.1.1.1 host address is up, the prefix 10.10.0.0/16 is injected into the local routing table as a static route with a DVSR subtype:

[local]Redback(config)#context local

[local]Redback(config-ctx)#dvsr-profile abc-web

[local]Redback(config-dvsr)#exit

[local]Redback(config-ctx)#ip route 10.10.0.0/16 10.1.1.1 dvsr abc-web

3.2   DVSR in Anycast Application

Figure 1 illustrates a network topology where a DVSR-enabled edge router, Router A, shares a LAN with two workstations in a webfarm.

Figure 1   Basic Anycast Network Topology

The W-a and W-b workstations serve applications with IP subnets of 12.12.12.0/24 and 100.100.100.100/32 as anycast addresses. (Somewhere else, other workstations also serve the same anycast addresses.) Edge Router A should announce those two anycast addresses only if workstations W-a and W-b are up. The anycast routes are redistributed into BGP.

The DVSR configuration for edge router A is as follows:

[local]Redback(config)#context local

[local]Redback(config-ctx)#dvsr-profile abc-webfarm

[local]Redback(config-dvsr)#ttl 2

[local]Redback(config-dvsr)#verify-set 30 timeout-multiplier 4 min-success 3

[local]Redback(config-dvsr)#exit

[local]Redback(config-ctx)#ip route 12.12.12.0/24 10.1.1.2 dvsr abc-webfarm

[local]Redback(config-ctx)#ip route 100.100.100.100/32 10.1.1.3 dvsr abc-webfarm

[local]Redback(config-ctx)#router bgp 65000

[local]Redback(config-bgp)#address-family ipv4 unicast

[local]Redback(config-addrfamily)#redistribute static dvsr

3.3   DVSR in Customer Multihoming Application

Figure 2 illustrates that an ISP has a customer network multihomed into edge router A and edge router B. The customer network has IP subnets 12.12.12.0/24, 12.12.25.0/23, and 158.10.10.0/24.

Figure 2   Basic Customer Multihoming Network Topology

Routers C-1 and C-2 do not run BGP, or any other dynamic routing protocol. DVSR is used in this case to inject customer routes into the backbone. If router C-1 or C-2 fails, or if customer internal links fail, routers A or B withdraws the DVSR routes, thus avoiding the blackholing of traffic towards the customer network.

The DVSR configuration for edge router A is as follows:

[local]Redback(config)#context local

[local]Redback(config-ctx)#dvsr-profile multi-home-c

[local]Redback(config-dvsr)#ttl 3

[local]Redback(config-dvsr)#tag 123

[local]Redback(config-dvsr)#exit

[local]Redback(config-ctx)#ip route 12.12.12.1/32 10.1.1.2

[local]Redback(config-ctx)#ip route 12.12.12.0/24 10.1.1.2 dvsr multi-home-c 12.12.12.1

[local]Redback(config-ctx)#ip route 12.12.25.0/23 10.1.1.2 dvsr multi-home-c 12.12.12.1

[local]Redback(config-ctx)#ip route 158.10.10.0/24 10.1.1.2 dvsr multi-home-c 12.12.12.1

[local]Redback(config-ctx)#router isis ip-backbone

[local]Redback(config-isis)#redistribute static dvsr

The DVSR configuration for edge router B is as follows:

[local]Redback(config)#context local

[local]Redback(config-ctx)#dvsr-profile multi-home-c

[local]Redback(config-dvsr)#ttl 3

[local]Redback(config-dvsr)#tag 123

[local]Redback(config-dvsr)#exit

[local]Redback(config-ctx)#ip route 158.10.10.1/32 10.10.10.3

[local]Redback(config-ctx)#ip route 12.12.12.0/24 10.10.10.3 dvsr multi-home-c 158.10.10.1

[local]Redback(config-ctx)#ip route 12.12.25.0/23 10.10.10.3 dvsr multi-home-c 158.10.10.1

[local]Redback(config-ctx)#ip route 158.10.10.0/24 10.10.10.3 dvsr multi-home-c 158.10.10.1

[local]Redback(config-ctx)#router isis ip-backbone

[local]Redback(config-isis)#redistribute static dvsr