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Configuring FRAS DLSw Backup

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Document ID: 12256


Contents

Introduction
Prerequisites
      Requirements
      Conventions
Configure
      Configuration Notes
      Network Diagram
      Network Diagram Notes
      Configurations
Verify
      Debug and Verification Tips
      Show Command Output
      FRAS States
Troubleshoot
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Introduction

In this sample configuration, a Cisco router configured for Frame Relay Access Support (FRAS) boundary network node (BNN) with Token Ring-attached devices communicates with a Frame Relay-attached front-end processor (FEP).

The objective is to configure and confirm the behavior of the FRAS data-link switching (DLSw) backup feature, introduced in Cisco IOS® Software Release 11.2F. This feature provides a secondary path (through DLSw+) that is used when the Frame Relay network becomes unavailable. When the primary FRAS connection fails, DLSw provides the desired connectivity, and the end stations connect to the Host with DLSw. Note that the FEP has a Token Ring connection that goes to the DLSw router.

Prerequisites

Requirements

There are no specific requirements for this document.

Conventions

Refer to Cisco Technical Tips Conventions for more information on document conventions.

Configure

Configuration Notes

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

  • The FRAS BNN router (AVIMI) to 0 MAC address must be configured as the destination MAC (DMAC) in all the end devices (0100.1111.0000).

  • If you use the old support for BNN (pre 11.2), you need to map every end station in the segment/ring.

    Note: The MAC address in the FRAS map command represents the end station: smac.

  • The FRAS BNN router configuration contains these commands:

    fras map llc 0000.1111.0000 4 4 Serial0 frame-relay 40 8 4

    fras map llc 0000.3333.0000 4 4 Serial0 frame-relay 40 4 4

    With these commands, the FRAS BNN router accepts inbound requests from the end stations (0000.1111.0000 and 0000.3333.0000) with SAP 0x04 that tries to connect to 0100.1111.0000 with SAP 0x04. On the Frame Relay side, the router sends data over DLCI 40, with a destination SAP (DSAP) of 0x04 and a SSAP of 0x08 and 0x04, respectively.

  • The FRAS BNN router configuration contains this command on interface serial 0:

    fras backup dlsw 4000.1000.2000 100 4000.3745.0000

    This command enables the FRAS DLSw backup feature. In case of a failure on the Frame Relay link, the router attempts to connect to the remote MAC 4000.3745.0000 through DLSw with ring 100 (virtual ring of the router). The router uses 4000.1000.2000 as the source MAC address. If multiple sessions need backup through DLSw, the router uses different SAPs for each one (see the Show Command Outputsection).

  • FRAS backup DLSw is an 11.2F feature of IOS.

  • When the main Frame Relay connection (FRAS) comes back up, the SNA sessions are maintained over DLSw. You must clear all the DLSw circuits in order to move them manually .

  • For this example, the Frame Relay connection was simulated back-to-back (no Frame Relay switch in the middle).

    Note: There are no Local Management Interfaces (LMIs) or keepalives configured.

Note: Use the Command Lookup Tool ( registered customers only) to find more information on the commands used in this document.

Network Diagram

This document uses this network setup:

frasdslw.gif

Network Diagram Notes

  • SNA Gateway A is configured with this Media Access Control (MAC) value: 

          smac = 0000.1111.0000 (non-cannonical)
      dmac = 0100.1111.0000 (non-cannonical)
      ssap = 0x04 and dsap = 0x04

  • SNA Gateway B is configured with this MAC value: 

          smac = 0000.3333.0000 (non-cannonical)
      dmac = 0100.1111.0000 (non-cannonical)
      ssap = 0x04 and dsap = 0x04

  • FEP has this MAC address on its Token Ring interface: 

    smac = 4000.3745.0000  (non-cannonical)

  • FRAS BNN router (AVIMI) has configured this MAC on its Token Ring interface: 

    smac = 0100.1111.0000  (non-cannonical)

  • For this test, the SNA Gateways connect to the Host with FRAS BNN through Serial 0 on the FRAS BNN router. The objective of FRAS DLSw backup is to keep connectivity to the Host with DLSw (through Serial 1) in case the main Frame Relay link goes down.

Configurations

This document uses these configurations:

FRAS BNN Router

 
avimimus#show running-config 

  Current configuration: 
  ! 
  hostname avimimus 
  ! 
  source-bridge ring-group 100 
  dlsw local-peer peer-id 10.10.15.1 
  dlsw remote-peer 0 tcp 10.10.16.1 
  !
  interface Loopback0 
   ip address 10.10.15.1 255.255.255.0 
   no ip directed-broadcast 
  ! 
  interface Serial0 
   no ip address 
   no ip directed-broadcast 
   encapsulation frame-relay IETF 
   no ip mroute-cache 
   no keepalive 
   no fair-queue 
   clockrate 2000000 
   frame-relay map llc2 40 
   frame-relay interface-dlci 40 
   fras backup dlsw 4000.1000.2000 100 4000.3745.0000 
  ! 
  interface Serial1 
   no ip address 
   no ip directed-broadcast 
   encapsulation frame-relay IETF 
   no keepalive 
  ! 
  interface Serial1.1 point-to-point 
   ip address 10.10.11.5 255.255.255.252 
   no ip directed-broadcast 
   frame-relay interface-dlci 20 
  ! 
  interface TokenRing0 
   mac-address 0100.1111.0000 
   no ip address 
   no ip directed-broadcast 
   ring-speed 16 
   source-bridge 2 8 100 
   fras map llc 0000.1111.0000 4 4 Serial0 frame-relay 40 8 4 
   fras map llc 0000.3333.0000 4 4 Serial0 frame-relay 40 4 4 
  ! 
  router eigrp 10 
   network 10.0.0.0 
  ! 
  end

DLSw Router at Host Side

 
limno#show running-config 

  Building configuration... 
  Current configuration: 
  ! 
  hostname limno 
  ! 
  source-bridge ring-group 500 
  dlsw local-peer peer-id 10.10.16.1 
  dlsw remote-peer 0 tcp 10.10.15.1 
  ! 
  interface Loopback0
   ip address 10.10.16.1 255.255.255.0 
   no ip directed-broadcast 
  ! 
  interface Serial1
   no ip address 
   no ip directed-broadcast 
   encapsulation frame-relay IETF 
   no ip route-cache 
   no ip mroute-cache 
   no keepalive 
   clockrate 4000000 
  ! 
  interface Serial1.1 point-to-point
   ip address 10.10.11.6 255.255.255.252 
   no ip directed-broadcast 
   no ip route-cache 
   no ip mroute-cache
   frame-relay interface-dlci 20 
  ! 
  interface TokenRing0 
   ip address 170.186.86.43 255.255.255.0 secondary 
   ip address 10.10.12.1 255.255.255.0 
   no ip directed-broadcast 
   no ip route-cache 
   no ip mroute-cache 
   ring-speed 16 
   source-bridge 10 1 500
   source-bridge spanning 
  ! 
  router eigrp 10 
  network 10.0.0.0 
  ! 
  end

Verify

Debug and Verification Tips

  • debug fras error - Displays information about FRAS protocol errors.

  • debug fras state - Displays information about FRAS data link control link state changes. These are the possible states: reset, request open station is sent, exchange xid, connection request is sent, signal station wait, connection response wait, connection response sent, connection established, disconnect wait, and number of link states.

  • debug fras message - Displays general information about FRAS messages.

Show Command Output

You can use these show commands to verify the configuration.

FRAS BNN router before the DLSw backup was activated

 
avimimus#show fras 


Boundary Network Node (BNN): 


DLCI: 40 
Type   Destination           Int    LSap        RSap        Role   State 
llc    0000.1111.0000        To0     4            4           P    ls_Contacted 
fr         -                 Se0     8            4           S    ls_Contacted 


DLCI: 40 
Type   Destination           Int    LSap       RSap         Role   State 
llc    0000.3333.0000        To0     4           4            P    ls_Contacted 
fr         -                 Se0     4           4            S    ls_Contacted 

Boundary Access Node (BAN):

avimimus#show llc2 brief
 
LLC2 Connections: total of 4 connections 
Se0 NORMAL 40 04 04 
Se0 NORMAL 40 08 04 
To0 NORMAL 0000.1111.0000 0100.1111.0000 04 04 
To0 NORMAL 0000.3333.0000 0100.1111.0000 04 04 

avimimus#show llc2 

LLC2 Connections: total of 4 connections 
Serial0 DTE: 40 04 04 state NORMAL 
V(S)=1, V(R)=1, Last N(R)=1, Local window=7, Remote Window=127 
akmax=3, n2=10, 
xid-retry timer 0/0 ack timer 0/1000 
p timer 0/1000 idle timer 2370/10000 
rej timer 0/3200 busy timer 0/9600 
akdelay timer 0/100 txQ count 0/200 

Serial0 DTE: 40 08 04 state NORMAL 
V(S)=1, V(R)=1, Last N(R)=1, Local window=7, Remote Window=127 
akmax=3, n2=10, 
xid-retry timer 0/0 ack timer 0/1000 
p timer 0/1000 idle timer 6590/10000 
rej timer 0/3200 busy timer 0/9600 
akdelay timer 0/100 txQ count 0/200 

TokenRing0 DTE: 0000.1111.0000 0100.1111.0000 04 04 state NORMAL 
V(S)=1, V(R)=1, Last N(R)=1, Local window=7, Remote Window=127 
akmax=3, n2=10, 
xid-retry timer 0/0 ack timer 0/1000 
p timer 0/1000 idle timer 8950/10000 
rej timer 0/3200 busy timer 0/9600 
akdelay timer 0/100 txQ count 0/200 

TokenRing0 DTE: 0000.3333.0000 0100.1111.0000 04 04 state NORMAL 
V(S)=1, V(R)=1, Last N(R)=1, Local window=7, Remote Window=127 
akmax=3, n2=10, 
xid-retry timer 0/0 ack timer 0/1000 
p timer 0/1000 idle timer 7370/10000 
rej timer 0/3200 busy timer 0/9600 
akdelay timer 0/100 txQ count 0/200

Note: At this stage there are no DLSw circuits. All connectivity is through FRAS BNN.

avimimus#show dlsw peer 

Peers:          state      pkts_rx   pkts_tx   type drops ckts TCP uptime 
TCP 10.10.16.1  CONNECT     46         46      conf  0     0    0  00:20:31 
Total number of connected peers: 1 
Total number of connections: 1

FRAS BNN router after the DLSw backup was activated

 
avimimus#show fras 

Boundary Network Node (BNN): 

DLCI: 40 
Type     Destination    Int      LSap    RSap   Role     State 
dlsw     -              Se0      8         4      S      ls_Contacted 
                                                         (Backup is enabled) 
llc      0000.1111.0000 To0      4         4      P      ls_Contacted 

DLCI: 40 
Type     Destination    Int    LSap     RSap     Role    State 
dlsw     -              Se0     4        4         S     ls_Contacted  
                                                         (Backup is enabled) 
llc      0000.3333.0000  To0    4        4         P     ls_Contacted 

Boundary Access Node (BAN): 
  

avimimus#show llc brief
 
LLC2 Connections: total of 2 connections 
To0 NORMAL 0000.1111.0000 0100.1111.0000 04 04 
To0 NORMAL 0000.3333.0000 0100.1111.0000 04 04 

avimimus#show llc
 
LLC2 Connections: total of 2 connections 
TokenRing0 DTE: 0000.1111.0000 0100.1111.0000 04 04 state NORMAL
V(S)=1, V(R)=1, Last N(R)=1, Local window=7, Remote Window=127
akmax=3, n2=10,
xid-retry timer 0/0 ack timer 0/1000
p timer 0/1000 idle timer 2210/10000
rej timer 0/3200 busy timer 0/9600
akdelay timer 0/100 txQ count 0/200


TokenRing0 DTE: 0000.3333.0000 0100.1111.0000 04 04 state NORMAL 
V(S)=1, V(R)=1, Last N(R)=1, Local window=7, Remote Window=127 
akmax=3, n2=10, 
xid-retry timer 0/0 ack timer 0/1000 
p timer 0/1000 idle timer 8900/10000 
rej timer 0/3200 busy timer 0/9600 
akdelay timer 0/100 txQ count 0/200

Note: After the FRAS failure, the LLC sessions terminated by the router are still between the end stations and the MAC configured in Token Ring 0 (0100.1111.0000), but the DLSw circuits are shown between the MAC addresses configured in the fras backup dlsw command

avimimus#show dlsw circuit detail 

Index       local addr(lsap)  remote addr(dsap)  state     uptime
1442840576  4000.1000.2000(04)4000.3745.0000(04) CONNECTED 00:04:07
PCEP: 617BE454 UCEP: 6170CFB8 
Port:VDLC100 peer 10.10.16.1(2065) 
Flow-Control-Tx CW:20, Permitted:19; Rx CW:20, Granted:39; Op: Repeat
Congestion: Low(02), Flow Op: Half: 0/0 Reset 0/0 
RIF = --no rif-- 
Bytes: 229/18 Info-frames: 1/1 
XID-frames: 3/1 UInfo-frames: 0/0 
  

1962934273  4000.1000.2000(08) 4000.3745.0000(04) CONNECTED 00:03:34 
PCEP: 6170D5F8 UCEP: 6175BC68 
Port:VDLC100 peer 10.10.16.1(2065) 
Flow-Control-Tx CW:20, Permitted:19; Rx CW:20, Granted:39; Op: Repeat 
Congestion: Low(02), Flow Op: Half: 0/0 Reset 0/0 
RIF = --no rif-- 
Bytes: 229/18 Info-frames: 1/1 
XID-frames: 3/1 UInfo-frames: 0/0 
Total number of circuits connected: 2 
  

avimimus#show dlsw circuit 

Index       local addr(lsap)   remote addr(dsap)    state       uptime 
1442840576  4000.1000.2000(04) 4000.3745.0000(04)   CONNECTED   00:13:39           
1962934273  4000.1000.2000(08) 4000.3745.0000(04)   CONNECTED   00:13:06  
          
Total number of circuits connected: 2

DLSw Router at Host Side

 
This is the data taken before the DLSw backup feature started. 
No DLSw circuits for this case. 
limno#show dlsw peer 

Peers:           state     pkts_rx   pkts_tx    type    drops  ckts TCP uptime 
TCP 10.10.15.1   CONNECT   48          48       conf     0      0    0  00:21:35 
Total number of connected peers: 1 
Total number of connections: 1 
  
This is the data after the DLSw backup feature starts to work. 
 
limno#show dlsw circuit  

Index         local addr(lsap)         remote addr(dsap)      state      uptime 
3338666589     4000.3745.0000(04)     4000.1000.2000(04)     CONNECTED   00:03:51 
1459618398     4000.3745.0000(04)     4000.1000.2000(08)     CONNECTED   00:03:18 
Total number of circuits connected: 2 
  

limno#show dlsw circuit detail 

Index          local addr(lsap)       remote addr(dsap)       state       uptime 
3338666589     4000.3745.0000(04)     4000.1000.2000(04)      CONNECTED   00:04:01 
PCEP: 54E3D0 UCEP: 54D0B4 
Port:To0 peer 10.10.15.1(2065) 
Flow-Control-Tx CW:20, Permitted:39; Rx CW:20, Granted:19; Op: Repeat 
Congestion: Low(02), Flow Op: Half: 0/0 Reset 0/0 
RIF = 0630.1F41.00A0 
Bytes: 18/229 Info-frames: 1/1 
XID-frames: 1/3 UInfo-frames: 0/0 
  

1459618398      4000.3745.0000(04)     4000.1000.2000(08)     CONNECTED     00:03:29 
PCEP: F7958 UCEP: 54BE94 
Port:To0 peer 10.10.15.1(2065) 
Flow-Control-Tx CW:20, Permitted:39; Rx CW:20, Granted:19; Op: Repeat 
Congestion: Low(02), Flow Op: Half: 0/0 Reset 0/0 
RIF = 0630.1F41.00A0 
Bytes: 18/229 Info-frames: 1/1 
XID-frames: 1/3 UInfo-frames: 0/0 
Total number of circuits connected: 2 
  

limno#show llc  

LLC2 Connections: total of 2 connections 
TokenRing0 DTE: 4000.3745.0000 4000.1000.2000 04 04 state NORMAL 
V(S)=1, V(R)=1, Last N(R)=1, Local window=7, Remote Window=127 
akmax=3, n2=8, 
xid-retry timer 0/0 ack timer 0/1000 
p timer 0/1000 idle timer 8200/10000 
rej timer 0/3200 busy timer 0/9600 
akdelay timer 0/100 txQ count 0/200 
RIF: 0630.1F41.00A0 
  

TokenRing0 DTE: 4000.3745.0000 4000.1000.2000 08 04 state NORMAL 
V(S)=1, V(R)=1, Last N(R)=1, Local window=7, Remote Window=127 
akmax=3, n2=8, 
xid-retry timer 0/0 ack timer 0/1000 
p timer 0/1000 idle timer 430/10000 
rej timer 0/3200 busy timer 0/9600 
akdelay timer 0/100 txQ count 0/200 
RIF: 0630.1F41.00A0 
  

limno#show llc brief 

LLC2 Connections: total of 2 connections 
To0 NORMAL 4000.3745.0000 4000.1000.2000 04 04 
RIF: 0630.1F41.00A0 
To0 NORMAL 4000.3745.0000 4000.1000.2000 08 04 
RIF: 06

The Output Interpreter Tool ( registered customers only) (OIT) supports certain show commands. Use the OIT to view an analysis of show command output.

FRAS States

These are the possible states for the FRAS connection. The output of show fras displays the current state. The states listed here appear in the same order as they happen in a successful connection sequence.

  • LS_RESET - Initial state.

  • LS_RQOPNSTNSENT - TEST frame sent; request to open a connection end point.

  • LS_EXCHGXID - XID negotiation takes place.

  • LS_CONNRQSENT - SABME sent (side that connects).

  • LS_SIGSTNWAIT - Waits for signal to clean up the congestion, and responds to polling with an RNR.

  • LS_CONNRSPWAIT - Waits for the other CEP (connection end point) to bring up the link.

  • LS_CONNRSPSENT - A UA has been sent and the router waits for an RR to clear up the flow.

  • LS_CONTACTED - Everything is connected.

  • LS_DISCWAIT - Wait for acknowledgement to disconnect request.

Troubleshoot

There is currently no specific troubleshooting information available for this configuration.

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Updated: Sep 09, 2005Document ID: 12256