OSPF Per-Interface Link-Local Signaling

The OSPF Per-Interface Link-Local Signaling feature allows you to selectively enable or disable Link-Local Signaling (LLS) for a specific interface regardless of the global (router level) setting that you have previously configured.

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Information About OSPF Per-Interface Link-Local Signaling

Benefits of the OSPF Per-Interface Link-Local Signaling Feature

LLS allows for the extension of existing OSPF packets in order to provide additional bit space. The additional bit space enables greater information per packet exchange between OSPF neighbors. This functionality is used, for example, by the OSPF Nonstop Forwarding (NSF) Awareness feature that allows customer premises equipment (CPE) routers that are NSF-aware to help NSF-capable routers perform nonstop forwarding of packets.

When LLS is enabled at the router level, it is automatically enabled for all interfaces. The OSPF Per-Interface Link-Local Signaling feature allows you to selectively enable or disable LLS for a specific interface. You may want to disable LLS on a per-interface basis depending on your network design. For example, disabling LLS on an interface that is connected to a non-Cisco device that may be noncompliant with RFC 2328 can prevent problems with the forming of Open Shortest Path First (OSPF) neighbors in the network.

How to Configure OSPF Per-Interface Link-Local Signaling

Turning Off LLS on a Per-Interface Basis

SUMMARY STEPS

    1.    enable

    2.    configure terminal

    3.    interface type slot /port

    4.    ip address ip-address mask [secondary]

    5.    no ip directed-broadcast [access-list-number | extended access-list-number]

    6.    ip ospf message-digest-key key-id encryption-type md5 key

    7.    [no | default] ip ospf lls [disable]


DETAILED STEPS
     Command or ActionPurpose
    Step 1 enable


    Example:
    Router> enable
     

    Enables privileged EXEC mode.

    • Enter your password if prompted.

     
    Step 2 configure terminal


    Example:
    Router# configure terminal
     

    Enters global configuration mode.

     
    Step 3 interface type slot /port


    Example:
    Router(config)# interface Ethernet 1/0


    Example:
    

        
    
 
          		 
          
    
Configures an interface type and enters interface configuration mode.
    

         
      
    

    Step 4
          
            ip
            address
          
          
            ip-address
          
          
            mask
           [secondary]
     

    Example:
    
          
    Router(config-if)# ip address 10.2.145.20 255.255.255.0
    

        
    
 
          		 
          
    
Sets a primary or secondary IP address for an interface.
    

         
      
    

    Step 5
          
            no
            ip
            directed-broadcast
           [access-list-number | extended access-list-number]
     

    Example:
    
          
    Router(config-if)# no ip directed-broadcast
    

        
    
 
          		 
          
    
Drops directed broadcasts destined for the subnet to which that interface is attached, rather than broadcasting them.
    

          
    • 
The forwarding of IP directed broadcasts on Ethernet interface 1/0 is disabled.
      

      • 

    

         
      
    

    Step 6
          
            ip
            ospf
            message-digest-key
          
          
            key-id
            encryption-type
          
          
            md5
          
          
            key
          
        
     

    Example:
    
          
    Router(config-if)# ip ospf message-digest-key 100 md5 testing
    

        
    
 
          		 
          
    
Enables OSPF Message Digest 5 (MD5) algorithm authentication.
    

         
      
    

    Step 7
[no | default] ip ospf lls [disable] 

    Example:
    
          
    Router(config-if)# ip ospf lls disable
    

        
    
 
          		 
          
    
Disables LLS on an interface, regardless of the global (router level) setting.
    

         
      
    

    

    

    What to Do Next
    

     To verify that LLS has been enabled or disabled for a specific interface, use the 
		show 
		  ip 
		  ospf 
		  interface command. See the "Example: Configuring and Verifying the OSPF Per-Interface Link-Local Signaling Feature" section for an example of the information displayed.
	 
    

    

    

    

    

    Configuration Examples for OSPF Per-Interface Link-Local Signaling
    

    
    
    

    

    Example  OSPF Per-Interface Link-Local Signaling
    

    
      
    
In the following example, LLS has been enabled on Ethernet interface 1/0 and disabled on Ethernet interface 2/0:
    

      
    interface Ethernet1/0
 ip address 10.2.145.2 255.255.255.0
 no ip directed-broadcast
 ip ospf message-digest-key 1 md5 testing
 ip ospf lls
!
interface Ethernet2/0
 ip address 10.1.145.2 255.255.0.0
 no ip directed-broadcast
 ip ospf message-digest-key 1 md5 testing
!
 ip ospf lls disable
interface Ethernet3/0
 ip address 10.3.145.2 255.255.255.0
 no ip directed-broadcast
!
router ospf 1
 log-adjacency-changes detail
 area 0 authentication message-digest
 redistribute connected subnets
 network 10.0.0.0 0.255.255.255 area 1
 network 10.2.3.0 0.0.0.255 area 1

    

      
    
In the following example, the show ip ospf interface command has been entered to verify that LLS has been enabled for Ethernet interface 1/0 and disabled for interface Ethernet 2/0:
    

      
    Router# show ip ospf interface
Ethernet1/0 is up, line protocol is up 
  Internet Address 10.2.145.2/24, Area 1 
  Process ID 1, Router ID 10.22.222.2, Network Type BROADCAST, Cost: 10
  Transmit Delay is 1 sec, State BDR, Priority 1 
  Designated Router (ID) 10.2.2.3, Interface address 10.2.145.1
  Backup Designated router (ID) 10.22.222.2, Interface address 10.2.145.2
  Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
    oob-resync timeout 40
    Hello due in 00:00:00
!   Supports Link-local Signaling (LLS)
Index 1/1, flood queue length 0
  Next 0x0(0)/0x0(0)
  Last flood scan length is 2, maximum is 8
  Last flood scan time is 0 msec, maximum is 0 msec
  Neighbor Count is 1, Adjacent neighbor count is 1 
    Adjacent with neighbor 10.2.2.3  (Designated Router)
  Suppress hello for 0 neighbor(s)
Ethernet2/0 is up, line protocol is up 
  Internet Address 10.1.145.2/16, Area 1 
  Process ID 1, Router ID 10.22.222.2, Network Type BROADCAST, Cost: 10
  Transmit Delay is 1 sec, State BDR, Priority 1 
  Designated Router (ID) 10.2.2.3, Interface address 10.1.145.1
  Backup Designated router (ID) 10.22.222.2, Interface address 10.1.145.2
  Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
    oob-resync timeout 40
    Hello due in 00:00:04
!   Does not support Link-local Signaling (LLS)
Index 2/2, flood queue length 0
  Next 0x0(0)/0x0(0)
  Last flood scan length is 2, maximum is 11
  Last flood scan time is 0 msec, maximum is 0 msec
  Neighbor Count is 1, Adjacent neighbor count is 1 
    Adjacent with neighbor 45.2.2.3  (Designated Router)
    Suppress hello for 0 neighbor(s)
Ethernet3/0 is up, line protocol is up 
  Internet Address 10.3.145.2/24, Area 1 
  Process ID 1, Router ID 10.22.222.2, Network Type BROADCAST, Cost: 10
  Transmit Delay is 1 sec, State BDR, Priority 1 
  Designated Router (ID) 10.2.2.3, Interface address 10.3.145.1
  Backup Designated router (ID) 10.22.222.2, Interface address 10.3.145.2
  Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
    oob-resync timeout 40
    Hello due in 00:00:07
!   Supports Link-local Signaling (LLS)
Index 3/3, flood queue length 0
  Next 0x0(0)/0x0(0)
  Last flood scan length is 2, maximum is 11
  Last flood scan time is 0 msec, maximum is 0 msec
  Neighbor Count is 1, Adjacent neighbor count is 1 
    Adjacent with neighbor 10.2.2.3  (Designated Router)
  Suppress hello for 0 neighbor(s)
    

    
    

    

    

    

    Additional References
    

     
		
     The following sections provide references related to the OSPF Per-Interface Link-Local Signaling feature.
		
    
 
	 
    

    Related Documents
     
		 
		

     
					 
     Related Topic
					 
    
 
				      		
 
					 
     Document Title
					 
    
 
				      		

    
    

     
					 
     Configuring OSPF 
					 
    
 
				      		
 
					 
    "Configuring OSPF" 
					 
    
 
				      		

    

     
					 
     Configuring OSPF NSF Awareness
					 
    
 
				      		
 
					 
    "NSF-OSPF"
					 
    
 
				      		

    

     
					 
     OSPF commands 
					 
    
 
				      		
 
					 
     Cisco IOS IP Routing: OSPF Command Reference 
						
					 
    
 
				      		

    
    

    

    
 
	 
    

    Standards
     
		 
		

     
					 
     Standards
					 
    
 
				      		
 
					 
     Title
					 
    
 
				      		

    
    

     
					 
     None
					 
    
 
				      		
 
					 
     --
					 
    
 
				      		

    
    

    

    
 
	 
    

    MIBs
     
		 
		

     
					 
     MIBs
					 
    
 
				      		
 
					 
     MIBs Link
					 
    
 
				      		

    
    

     
					 
     None
					 
    
 
				      		
 
					 
     To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL:
					 
    
 
					 
     
						http:/​/​www.cisco.com/​go/​mibs 
					 
    
 
				      		

    
    

    

    
 
	 
    

    RFCs
     
		 
		

     
					 
     RFCs
					 
    
 
				      		
 
					 
     Title
					 
    
 
				      		

    
    

     
					 
     RFC 2328
					 
    
 
				      		
 
					 
     
						OSPF Version 2 
					 
    
 
				      		

    
    

    

    
 
	 
    

    Technical Assistance
     
		 
		

     
					 
     Description
					 
    
 
				      		
 
					 
     Link
					 
    
 
				      		

    
    

     
					 
     The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password. 
					 
    
 
				      		
 
					 
     
						http:/​/​www.cisco.com/​cisco/​web/​support/​index.html 
					 
    
 
				      		

    
    

    

    
 
	 
    

    

    

    Feature Information for OSPF Per-Interface Link-Local Signaling
    

     
		
    The following table
		  provides release information about the feature or features described in this
		  module. This table lists only the software release that introduced support for
		  a given feature in a given software release train. Unless noted otherwise,
		  subsequent releases of that software release train also support that feature. 
		
    
 Use Cisco Feature Navigator to find information about platform
		support and Cisco software image support. To access Cisco Feature Navigator, go
		to 
		.
		An account on Cisco.com is not required. 
	 
    

     
		

    Table 1 Feature Information for OSPF Per-Interface Link-Local Signaling 
     
				  
     Feature Name
				  
    
 
				    		
 
				  
     Releases
				  
    
 
				    		
 
				  
     Feature Information
				  
    
 
				    		

    
    

     
				  
     OSPF Per-Interface Link-Local Signaling
				  
    
 
				    		
 
				  
     12.0(27)S 12.3(7)T 12.2(25)S 12.2(18)SXE 12.2(27)SBC 12.2(33)SRA
				  
    
 
				    		
 
				  
     The OSPF Per-Interface Link-Local Signaling feature allows you to selectively enable or disable Link-Local Signaling (LLS) for a specific interface regardless of the global (router level) setting that you have previously configured.
				  
    
 
				  
     The following command was introduced or modified: 
					 ip 
						ospf 
						lls.