Category: CCNA Study Guide
Command Neighbor Use This command tells OSPF to communicate with unicast updates to a specific neighbor. This is particularly useful over non-broadcast links, such as frame-relay, as adjacenies will not form by default. Syntax Router(config-router)#neighbor <ip address> Example In this example, we will configure R4 to send its …
Command Auto-Cost Reference-Bandwidth Use Changes how OSPF calculates its metric. By default, a FastEthernet and above will have a cost of 1, so a gigabit interface will be equal with a fastethernet. This is not ideal. Syntax Router(config-router)#auto-cost reference-bandwidth <bandwidth> Example In this example, we will configure OSPF …
Command Passive-Interface Default Use This command prevents OSPF from forming adjacencies on all interfaces on the router. Using no passive interface default command is used to allow OSPF communication. Syntax Router(config-router)#passive-interface default Example In this example, we will use passive-interface default to block all OSPF adjacencies. Afterwards, we will allow communication through …
Command Network Use Specifies which interfaces will participate in the OSPF process. Syntax Router(config-router)#network <network address> <wildcard mask> area <area> Options <network address> Any interface with this network address will be added into OSPF. <wildcard masks> Sets how specific the network statement is: 192.168.1.0 0.0.0.255 would match any …
Command Distance OSPF Use This command changes the administrative distance for OSPF routes. Syntax Router(config-router)#distance ospf <intra-area distance><inter-area distance><external distance> Example In this example, we will change OSPF administrative distance to 150 for internal routes and 220 for external. Currently, we see OSPF is at its default administrative distance of 110. …
Command Distribute-List Use Allows you to filter routes from the routing table. For CCNA purposes, this is usually done through access lists. Syntax Router(config-router)#distribute-list <list> <in/out> OR Router(config-router)#distribute-list <list> <in/out> <interface> Options <list> Access list <in/out> Whether the router is receiving or sending the route Example In this …
Command Router-Id Use This command manually sets the router-id used by OSPF. If it is not set, OSPF will automatically set its router-id to be the highest loopback IP address or the highest IP address (if no loopback interfaces are present). One thing to note is, even though …
Command Distance Use Allows you to filter routes from the routing table. For CCNA purposes, this is usually done through access lists. Syntax Router(config-router)#distance <AD> <source IP> <wildcard mask> <access-list> Options <Administrative Distance> Sets the administrative distance for the selected routes <source IP> Source IP the route is …
Command Maximum-Paths Use Controls how many equal cost paths OSPF will loadbalance with. Syntax Router(config-router)#maximum-path <1-16> Example In this example we will change the number of OSPF maximum paths to 6. R1(config)#router OSPF 1 R1(config-router)# maximum-paths 6
Command Passive-Interface Use This command prevents OSPF from forming adjacencies on specified interfaces on the router. Using no passive-interface is used to allow all OSPF communication. Syntax Router(config-router)#passive-interface <interface> Example In this example, we will use passive-interface default to block all OSPF adjacencies. After that, we will allow communication through R2’s Fa0/0. …
