Load Balancing Over Several X.25 VCs Using the x25 nvc Command [X.25 Protocols]

Document ID: 18883

Introduction
Prerequisites
      Requirements
      Components Used
      Related Products
      Conventions
Configure
      Network Diagram
      Configurations
Verify
Troubleshoot
      Troubleshooting Commands
Related Information

Introduction

This document provides a sample configuration for load balancing over X.25 VCs using the x25 nvc command.

You can load-balance traffic bound for the same X.25 destination using either the x25 nvc command for global traffic, or from the x25 map nvc command option for a specific type of traffic.

The maximum number of virtual circuits (VCs) is eight (the default is one).

For more information on how calls are triggered and the load-balancing and backup features for X.25, refer to Load Balancing and BackUp Over X.25.

Note: The number of Networked Value Chains (NVCs) should match on both sides. If this is not the case, it can trigger inconsistent behavior, such as the remote site continuously clearing X.25 calls for one particular site.

Prerequisites

Requirements

Before attempting this configuration, ensure that you meet these requirements:

Basic knowledge of X.25
Configuring X.25
Load Balancing and Backup Over X.25

Please refer to the Related Information section for more details.

Components Used

The information in this document is based on these software and hardware versions:

Cisco 2503 and 2520 routers in a lab environment with cleared configurations.
Cisco IOS® Software Release 12.2(10b) was running on both routers.

The information in this document was created from the devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If your network is live, make sure that you understand the potential impact of any command.

Related Products

This configuration can be used with any two routers with one WAN serial interface each. WIC-1T, WIC-2T and fixed WAN serial interfaces can be used.

Conventions

For more information on document conventions, refer to Cisco Technical Tips Conventions.

Configure

In this section, you are presented with the information to configure the features described in this document.

Note: To find additional information on the commands used in this document, use the Command Lookup Tool (registered customers only) .

Network Diagram

This document uses this network setup:

Configurations

This document uses these configurations:

Router 1 (Cisco 2520 Router)

version 12.2
service timestamps debug datetime msec
service timestamps log datetime msec
!
hostname Router1
!
enable password <password>
!
!
x25 routing

!--- Enable x25 routing.

!
!
interface Ethernet0 
ip address 10.48.74.27 255.255.255.0
!
interface Serial0
 ip address 192.168.0.1 255.255.255.252
 encapsulation x25 
 no ip mroute-cache 
 x25 address 800
 x25 nvc 3

!--- In this case, the number of NVCs is set to three.

 x25 map ip 192.168.0.2 900
!
!
x25 route ^900 interface Serial0

!--- The Caret symbol ^ indicates that any packet with 
!--- X25 address beginning with 900 should
!--- be routed over the serial interface 0.

!
!
line con 0 
  exec-timeout 0 0
line aux 0
line vty 0 4 
  transport input all
!
end

Router2 (Cisco 2503 Router)

version 12.2
service timestamps debug datetime msec
service timestamps log datetime msec
!
hostname Router2
!
enable password <password>

x25 routing                     

!--- Enable X.25 routing.

!
!
interface Ethernet0
 ip address 172.16.0.1 255.255.255.0
!
interface Serial1
 ip address 192.168.0.2 255.255.255.252
 encapsulation x25 dce 
 x25 address 900
 x25 nvc 8

!--- Maximum number of NVCs used (range from one to eight).

 x25 map ip 192.168.0.1 800 nvc 3

!--- Maximum number of NVCs for this specific traffic.

clockrate 64000
!
x25 route ^800 interface serial 1
!
line con 0 
  exec-timeout 0 0
line aux 0
line vty 0 4 
  exec-timeout 0 0 
  password ww
!
end

Verify

This section provides information you can use to confirm your configuration is working properly.

Certain show commands are supported by the Output Interpreter Tool (registered customers only) , which allows you to view an analysis of show command output.

show x25 route—Displays the X.25 routing table.
show x25 vc—Displays information about active switched virtual circuits (SVCs) and permanent virtual circuits (PVCs).

Router2#show x25 route  
      #  Match                         Substitute    Route to  
      1  dest ^800                                   Serial1

The above show x25 route command output has the X.25 routing table information of Router2. It says that any packet with X.25 address beginning with 800 from Router2 should be routed over serial interface 1.

Troubleshoot

This section provides information you can use to troubleshoot your configuration.

Troubleshooting Commands

Certain show commands are supported by the Output Interpreter Tool (registered customers only) , which allows you to view an analysis of show command output.

Note: Before issuing debug commands, refer to Important Information on Debug Commands.

Configure timestamps in the global configuration as follows:

service timestamps debug datetime msec
service timestamps log datetime msec

Use the following commands for troubleshooting:

debug x25 events—Displays information on all X.25 traffic except X.25 data or acknowledgment packets.

Router2#debug x25 events
X.25 special event debugging is on

Router2#show debug
X.25:  
X.25 special event debugging is on

Router1#ping
Protocol [ip]:
Target IP address: 192.168.0.2
Repeat count [5]:10
Datagram size [100]: 5000
Timeout in seconds [2]:
Extended commands [n]:
Sweep range of sizes [n]:
Type escape sequence to abort.
Sending 5, 5000-byte ICMP Echos to 192.168.0.2, timeout is 2 seconds:
!!!!!!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1396/1408/1428 ms

The output of the debug x25 events on Router2 shows the traffic coming from the remote router Router1 (two calls have already been generated).

*Mar  1 04:58:42.350: Serial1: X.25 I R1 Call (12) 8 lci 1
*Mar  1 04:58:42.354:   From (3): 800 To (3): 900

!--- The first call originates from Router1 and a virtual 


!--- circuit is created.

*Mar  1 04:58:42.358:   Facilities: (0)
*Mar  1 04:58:42.358:   Call User Data (4): 0xCC000000 (ip)
*Mar  1 04:58:42.366: Serial1: X.25 O R1 Call Confirm (3) 8 lci 1
*Mar  1 04:58:42.410: Serial1: X.25 I R1 Call (12) 8 lci 2
*Mar  1 04:58:42.410:   From (3): 800 To (3): 900

!--- The second call originates from Router1 and the second 



!--- virtual circuit is created.

*Mar  1 04:58:42.414:   Facilities: (0)
*Mar  1 04:58:42.414:   Call User Data (4): 0xCC000000 (ip)
*Mar  1 04:58:42.422: Serial1: X.25 O R1 Call Confirm (3) 8 lci 2

When X.25 packets start being queued and the third calls are triggered by this router Router2 (which has first received the session) we see the following output:

*Mar  1 04:58:43.178: Serial1: X.25 O R1 Call (12) 8 lci 1024
*Mar  1 04:58:43.182:   From (3): 900 To (3): 800

!--- The third call originates from Router2 to Router1 and


!--- third virtual circuit is created reaching the


!--- maximum limit of 3 NVCs configured in Router2.

*Mar  1 04:58:43.186:   Facilities: (0)
*Mar  1 04:58:43.186:   Call User Data (4): 0xCC000000 (ip)
*Mar  1 04:58:43.198: Serial1: X.25 I R1 Call Confirm (5) 8 lci 1024
*Mar  1 04:58:43.202:   From (0):  To (0):
*Mar  1 04:58:43.202:   Facilities: (0)

We have now reached the maximum number of NVCs for this setup:

Router2#show x25 vc
SVC 1,  State: D1,  Interface: Serial1  
  Started 00:01:48, last input 00:01:34, output 00:01:34  
  Connects 800 <-> ip 192.168.0.1  
  Call PID ietf, Data PID none  
  Window size input: 2, output: 2  
  Packet size input: 128, output: 128  
  PS: 0  PR: 0  ACK: 0  Remote PR: 0  RCNT: 0  RNR: no  
  P/D state timeouts: 0  timer (secs): 0  
  data bytes 30000/30000 packets 240/240 Resets 0/0 RNRs 0/0 REJs 0/0 INTs 0/0
SVC 2,  State: D1,  Interface: Serial1
  Started 00:01:48, last input 00:01:34, output 00:01:34
  Connects 800 <-> ip 192.168.0.1
  Call PID ietf, Data PID none
  Window size input: 2, output: 2
  Packet size input: 128, output: 128
  PS: 2  PR: 5  ACK: 5  Remote PR: 1  RCNT: 0  RNR: no
  P/D state timeouts: 0  timer (secs): 0
  data bytes 20600/20040 packets 170/165 Resets 0/0 RNRs 0/0 REJs 0/0 INTs 0/0
SVC 1024,  State: D1,  Interface: Serial1
  Started 00:01:47, last input 00:01:39, output never
  Connects 800 <-> ip 192.168.0.1
  Call PID cisco, Data PID none
  Window size input: 2, output: 2
  Packet size input: 128, output: 128
  PS: 0  PR: 5  ACK: 4  Remote PR: 0  RCNT: 1  RNR: no
  P/D state timeouts: 0  timer (secs): 0
  data bytes 0/560 packets 0/5 Resets 0/0 RNRs 0/0 REJs 0/0 INTs 0/0

The above show x25 vc command output displays the active Switched Virtual Circuits svc1, svc2, and svc 1024 in Router2, which is established with Router1 over the serial interface 1. It also shows with which X.25 address (x25 address 800) it is connecting and the IP address (192.168.0.1) of the remote side.

Related Information

Updated: Dec 12, 2007

Document ID: 18883

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