ICND1 | Interconnecting Cisco Networking Devices 1

The ipv6 route 2001:DB8:A01::/48 Gi0/1 2001:DB8:D1A5:C900::1 command is used to create a static route. A static route has an administrative distance of 1 A static route outlines the remote network, the outgoing interface used to get to the remote destination, and the next hop address.

The ipv6 route ::/0 Gi0/1 2001:DB8:D1A5:C900::1 command configures a default route. Although similar in function to a static route, a default route merely forwards all data to that interface. Default routing should only be used when necessary. The ipv6 address autoconfig [default] command configures stateless autoconfiguration for an interface. Stateless autoconfiguration uses neighbor discovery mechanisms to find routers and dynamically create IPv6 addresses. Although the ipv6 route 2001:0DB8::/32 Gi0/1 130 command configures a floating static route, it applies an administrative distance of 130 to the route. RIP has an AD of 120. This type of command would be used to enable routing in the event that there is a problem with the routing protocol.

The ipv6 route 2001:DB8:A01::/48 Gi0/1 2001:DB8:D1A5:C900::1 command is used to create a static route. A static route has an administrative distance of 1 A static route outlines the remote network, the outgoing interface used to get to the remote destination, and the next hop address.

The ipv6 route ::/0 Gi0/1 2001:DB8:D1A5:C900::1 command configures a default route. Although similar in function to a static route, a default route merely forwards all data to that interface. Default routing should only be used when necessary. The ipv6 address autoconfig [default] command configures stateless autoconfiguration for an interface. Stateless autoconfiguration uses neighbor discovery mechanisms to find routers and dynamically create IPv6 addresses. Although the ipv6 route 2001:0DB8::/32 Gi0/1 130 command configures a floating static route, it applies an administrative distance of 130 to the route. RIP has an AD of 120. This type of command would be used to enable routing in the event that there is a problem with the routing protocol.

The ipv6 route 2001:DB8:A01::/48 Gi0/1 2001:DB8:D1A5:C900::1 command is used to create a static route. A static route has an administrative distance of 1 A static route outlines the remote network, the outgoing interface used to get to the remote destination, and the next hop address.

The ipv6 route ::/0 Gi0/1 2001:DB8:D1A5:C900::1 command configures a default route. Although similar in function to a static route, a default route merely forwards all data to that interface. Default routing should only be used when necessary. The ipv6 address autoconfig [default] command configures stateless autoconfiguration for an interface. Stateless autoconfiguration uses neighbor discovery mechanisms to find routers and dynamically create IPv6 addresses. Although the ipv6 route 2001:0DB8::/32 Gi0/1 130 command configures a floating static route, it applies an administrative distance of 130 to the route. RIP has an AD of 120. This type of command would be used to enable routing in the event that there is a problem with the routing protocol.

Performing a reload means resequencing the numbers. By default, the numbers increment by 10, which means after re-sequencing, the numbers will be 10, 20, 30, 40. You can also use the access-list resequence command to renumber the ACL entries in an ACL without having to reload.

The other options do not represent the new sequence numbers after performing a reload.
Performing a reload means resequencing the numbers. By default, the numbers increment by 10, which means after re-sequencing, the numbers will be 10, 20, 30, 40. You can also use the access-list resequence command to renumber the ACL entries in an ACL without having to reload.

The other options do not represent the new sequence numbers after performing a reload.
Performing a reload means resequencing the numbers. By default, the numbers increment by 10, which means after re-sequencing, the numbers will be 10, 20, 30, 40. You can also use the access-list resequence command to renumber the ACL entries in an ACL without having to reload.

The other options do not represent the new sequence numbers after performing a reload.

An Access Point (AP) is a device that allows wireless devices to connect to a wired network. An AP can be standalone, or be connected to a WLAN controller. These controllers are the devices that network administrators or network operations centers use to manage access points in large quantities. The WLAN controller automatically handles the configuration of wireless access points.

For a large size build, you could have 10-100 access points depending on your coverage. So the ability to control one or all of the access points from a central location is key. We are only concerned about the network for mobile devices such as laptops, therefore APs and WLAN controllers should be deployed. The number of WLAN controllers depends on how many access points are present on the network.
An Access Point (AP) is a device that allows wireless devices to connect to a wired network. An AP can be standalone, or be connected to a WLAN controller. These controllers are the devices that network administrators or network operations centers use to manage access points in large quantities. The WLAN controller automatically handles the configuration of wireless access points.

For a large size build, you could have 10-100 access points depending on your coverage. So the ability to control one or all of the access points from a central location is key. We are only concerned about the network for mobile devices such as laptops, therefore APs and WLAN controllers should be deployed. The number of WLAN controllers depends on how many access points are present on the network.
An Access Point (AP) is a device that allows wireless devices to connect to a wired network. An AP can be standalone, or be connected to a WLAN controller. These controllers are the devices that network administrators or network operations centers use to manage access points in large quantities. The WLAN controller automatically handles the configuration of wireless access points.

For a large size build, you could have 10-100 access points depending on your coverage. So the ability to control one or all of the access points from a central location is key. We are only concerned about the network for mobile devices such as laptops, therefore APs and WLAN controllers should be deployed. The number of WLAN controllers depends on how many access points are present on the network.

A switch builds and maintains a table, which is called a MAC table. This table matches a destination MAC address with the port that is used to connect to a node. For each incoming frame, the destination MAC address in the frame header is compared to the list of addresses in the MAC table. Switches then use MAC addresses as they decide whether to filter, forward, or flood frames.
A switch builds and maintains a table, which is called a MAC table. This table matches a destination MAC address with the port that is used to connect to a node. For each incoming frame, the destination MAC address in the frame header is compared to the list of addresses in the MAC table. Switches then use MAC addresses as they decide whether to filter, forward, or flood frames.
A switch builds and maintains a table, which is called a MAC table. This table matches a destination MAC address with the port that is used to connect to a node. For each incoming frame, the destination MAC address in the frame header is compared to the list of addresses in the MAC table. Switches then use MAC addresses as they decide whether to filter, forward, or flood frames.

To perform inter-VLAN routing functions, the router must know how to reach all VLANs that are being interconnected. There must be a separate logical connection on the router for each VLAN and VLAN trunking, such as IEEE 802.1Q, must be enabled on those connections. The encapsulation dot1q 20 command enables 802.1Q encapsulation trunking on the current subinterface. The value 20 represents the VLAN number (VLAN identifier). As best practice states, you would create the sub-interface, then set the encapsulation.

The switchport mode interface configuration command sets the interface type. The trunk parameter configures the port into permanent 802.1Q trunk mode and negotiates with the connected device to convert the link to trunk mode. The switchport mode interface configuration command sets the interface type on the switch. The access parameter disables port trunk mode and negotiates with the connected device to convert the link to nontrunk. The show vlans command displays the information about the Cisco IOS VLAN subinterfaces.
To perform inter-VLAN routing functions, the router must know how to reach all VLANs that are being interconnected. There must be a separate logical connection on the router for each VLAN and VLAN trunking, such as IEEE 802.1Q, must be enabled on those connections. The encapsulation dot1q 20 command enables 802.1Q encapsulation trunking on the current subinterface. The value 20 represents the VLAN number (VLAN identifier). As best practice states, you would create the sub-interface, then set the encapsulation.

The switchport mode interface configuration command sets the interface type. The trunk parameter configures the port into permanent 802.1Q trunk mode and negotiates with the connected device to convert the link to trunk mode. The switchport mode interface configuration command sets the interface type on the switch. The access parameter disables port trunk mode and negotiates with the connected device to convert the link to nontrunk. The show vlans command displays the information about the Cisco IOS VLAN subinterfaces.
To perform inter-VLAN routing functions, the router must know how to reach all VLANs that are being interconnected. There must be a separate logical connection on the router for each VLAN and VLAN trunking, such as IEEE 802.1Q, must be enabled on those connections. The encapsulation dot1q 20 command enables 802.1Q encapsulation trunking on the current subinterface. The value 20 represents the VLAN number (VLAN identifier). As best practice states, you would create the sub-interface, then set the encapsulation.

The switchport mode interface configuration command sets the interface type. The trunk parameter configures the port into permanent 802.1Q trunk mode and negotiates with the connected device to convert the link to trunk mode. The switchport mode interface configuration command sets the interface type on the switch. The access parameter disables port trunk mode and negotiates with the connected device to convert the link to nontrunk. The show vlans command displays the information about the Cisco IOS VLAN subinterfaces.

It is common, and often desirable, for DHCP servers and clients to reside on different subnets. Instead of using a different DHCP server for each subnet, you might want to use a centralized DHCP solution using a DCHP relay agent. The DHCP relay agent is configured with the DHCP server IP address on the interface that can reach the client to help manage IP address assignments for clients on different subnets. The command to configure the relay agent is:

ip helper-address ip-address

While the other commands relate to DHCP, they are not required to configure a DHCP relay agent.
It is common, and often desirable, for DHCP servers and clients to reside on different subnets. Instead of using a different DHCP server for each subnet, you might want to use a centralized DHCP solution using a DCHP relay agent. The DHCP relay agent is configured with the DHCP server IP address on the interface that can reach the client to help manage IP address assignments for clients on different subnets. The command to configure the relay agent is:

ip helper-address ip-address

While the other commands relate to DHCP, they are not required to configure a DHCP relay agent.
It is common, and often desirable, for DHCP servers and clients to reside on different subnets. Instead of using a different DHCP server for each subnet, you might want to use a centralized DHCP solution using a DCHP relay agent. The DHCP relay agent is configured with the DHCP server IP address on the interface that can reach the client to help manage IP address assignments for clients on different subnets. The command to configure the relay agent is:

ip helper-address ip-address

While the other commands relate to DHCP, they are not required to configure a DHCP relay agent.

The restrict violation mode also drops packets with unknown source addresses until you remove enough secure MAC addresses to drop below the maximum value. However, it also generates a log message and causes the security violation counter to increment.

The protect violation mode drops packets with unknown source addresses until you remove enough secure MAC addresses to drop below the maximum value. It does not keep a running count of packets dropped. The shutdown violation mode puts the interface into an error-disabled state immediately. Error-disabled is not a port violation mode, but a state that is caused from the shutdown violation mode.
The restrict violation mode also drops packets with unknown source addresses until you remove enough secure MAC addresses to drop below the maximum value. However, it also generates a log message and causes the security violation counter to increment.

The protect violation mode drops packets with unknown source addresses until you remove enough secure MAC addresses to drop below the maximum value. It does not keep a running count of packets dropped. The shutdown violation mode puts the interface into an error-disabled state immediately. Error-disabled is not a port violation mode, but a state that is caused from the shutdown violation mode.
The restrict violation mode also drops packets with unknown source addresses until you remove enough secure MAC addresses to drop below the maximum value. However, it also generates a log message and causes the security violation counter to increment.

The protect violation mode drops packets with unknown source addresses until you remove enough secure MAC addresses to drop below the maximum value. It does not keep a running count of packets dropped. The shutdown violation mode puts the interface into an error-disabled state immediately. Error-disabled is not a port violation mode, but a state that is caused from the shutdown violation mode.

A unique local address (defined in RFC 4193) is designed for use in local networks and is not intended to be routable in the global Internet. It is an IPv6 unicast address that is a substitute for a site-local address, and it uses the prefix FC00::/7 (1111 110). The eighth bit is always set to 0, and may be set to 1 in the future. The next 40 bits form the Global ID, a globally unique prefix that indicates the site. This Global ID is allocated pseudo-randomly to minimize the possibility of overlap with other sites. The unique local address is more functional than the site-local address because this prefix is globally unique, in a network where each site may commonly have more than one of these prefixes and may use them at the same time.

Site-Local addresses reside in the FEC0::/10 range and are not intended to be routable on the Internet. Link-local addresses refer only to a particular physical link (physical network). The IPv6 global unicast address is the equivalent of the IPv4 global unicast address. A global unicast address is an IPv6 address from the global unicast prefix.
A unique local address (defined in RFC 4193) is designed for use in local networks and is not intended to be routable in the global Internet. It is an IPv6 unicast address that is a substitute for a site-local address, and it uses the prefix FC00::/7 (1111 110). The eighth bit is always set to 0, and may be set to 1 in the future. The next 40 bits form the Global ID, a globally unique prefix that indicates the site. This Global ID is allocated pseudo-randomly to minimize the possibility of overlap with other sites. The unique local address is more functional than the site-local address because this prefix is globally unique, in a network where each site may commonly have more than one of these prefixes and may use them at the same time.

Site-Local addresses reside in the FEC0::/10 range and are not intended to be routable on the Internet. Link-local addresses refer only to a particular physical link (physical network). The IPv6 global unicast address is the equivalent of the IPv4 global unicast address. A global unicast address is an IPv6 address from the global unicast prefix.
A unique local address (defined in RFC 4193) is designed for use in local networks and is not intended to be routable in the global Internet. It is an IPv6 unicast address that is a substitute for a site-local address, and it uses the prefix FC00::/7 (1111 110). The eighth bit is always set to 0, and may be set to 1 in the future. The next 40 bits form the Global ID, a globally unique prefix that indicates the site. This Global ID is allocated pseudo-randomly to minimize the possibility of overlap with other sites. The unique local address is more functional than the site-local address because this prefix is globally unique, in a network where each site may commonly have more than one of these prefixes and may use them at the same time.

Site-Local addresses reside in the FEC0::/10 range and are not intended to be routable on the Internet. Link-local addresses refer only to a particular physical link (physical network). The IPv6 global unicast address is the equivalent of the IPv4 global unicast address. A global unicast address is an IPv6 address from the global unicast prefix.

For a trunk link to be established, both ends of the trunk link must be configured to use the same native VLAN. Cisco Discovery Protocol (CDP) will present a native VLAN mismatch error message if the native VLANs do not match. To display the status of the trunk and the native VLAN used on that trunk link, and to verify trunk establishment, you can use the show interface trunk command in privileged EXEC mode on both switches.

The show cdp neighbors command is used to display information about neighboring devices. This information includes Neighbor device ID; Local interface; Hold time value, in seconds; Neighbor device capability code; Neighbor hardware platform; and Neighbor remote port ID. It will not display information related to the native VLAN mismatch issue.
For a trunk link to be established, both ends of the trunk link must be configured to use the same native VLAN. Cisco Discovery Protocol (CDP) will present a native VLAN mismatch error message if the native VLANs do not match. To display the status of the trunk and the native VLAN used on that trunk link, and to verify trunk establishment, you can use the show interface trunk command in privileged EXEC mode on both switches.

The show cdp neighbors command is used to display information about neighboring devices. This information includes Neighbor device ID; Local interface; Hold time value, in seconds; Neighbor device capability code; Neighbor hardware platform; and Neighbor remote port ID. It will not display information related to the native VLAN mismatch issue.
For a trunk link to be established, both ends of the trunk link must be configured to use the same native VLAN. Cisco Discovery Protocol (CDP) will present a native VLAN mismatch error message if the native VLANs do not match. To display the status of the trunk and the native VLAN used on that trunk link, and to verify trunk establishment, you can use the show interface trunk command in privileged EXEC mode on both switches.

The show cdp neighbors command is used to display information about neighboring devices. This information includes Neighbor device ID; Local interface; Hold time value, in seconds; Neighbor device capability code; Neighbor hardware platform; and Neighbor remote port ID. It will not display information related to the native VLAN mismatch issue.

Static routes are routes that are manually entered into a routing table by an administrator. Static routes specify the path that packets take when moving between a source and a destination and are commonly used when routing from a network to a stub network. A static route can be configured by using the ip route command. The assignment of a static route to reach the stub network 172.16.1.0 is proper for Router A because there is only one way to reach that network. When configuring a static route, you need to include the network address and subnet mask of the remote network, along with the IP address of the next-hop router or the exit interface of the router you are configuring. To configure a static route using the next-hop router, you can use either of the following commands:

RouterA(config)#ip route 172.16.1.0 255.255.255.0 172.16.2.1

Or

RouterA(config)#ip route 172.16.1.0 255.255.255.0 serial0/0/0
Static routes are routes that are manually entered into a routing table by an administrator. Static routes specify the path that packets take when moving between a source and a destination and are commonly used when routing from a network to a stub network. A static route can be configured by using the ip route command. The assignment of a static route to reach the stub network 172.16.1.0 is proper for Router A because there is only one way to reach that network. When configuring a static route, you need to include the network address and subnet mask of the remote network, along with the IP address of the next-hop router or the exit interface of the router you are configuring. To configure a static route using the next-hop router, you can use either of the following commands:

RouterA(config)#ip route 172.16.1.0 255.255.255.0 172.16.2.1

Or

RouterA(config)#ip route 172.16.1.0 255.255.255.0 serial0/0/0
Static routes are routes that are manually entered into a routing table by an administrator. Static routes specify the path that packets take when moving between a source and a destination and are commonly used when routing from a network to a stub network. A static route can be configured by using the ip route command. The assignment of a static route to reach the stub network 172.16.1.0 is proper for Router A because there is only one way to reach that network. When configuring a static route, you need to include the network address and subnet mask of the remote network, along with the IP address of the next-hop router or the exit interface of the router you are configuring. To configure a static route using the next-hop router, you can use either of the following commands:

RouterA(config)#ip route 172.16.1.0 255.255.255.0 172.16.2.1

Or

RouterA(config)#ip route 172.16.1.0 255.255.255.0 serial0/0/0

For a trunk link to be established, both ends of the trunk link must be configured to use the same native VLAN. Cisco Discovery Protocol (CDP) will present a native VLAN mismatch error message if the native VLANs do not match. To display the status of the trunk and the native VLAN used on that trunk link, and to verify trunk establishment, you can use the show interface trunk command in privileged EXEC mode.

Cisco Discovery Protocol (CDP) exchanges hardware and software device information with its directly connected CDP neighbors. Although this is a useful troubleshooting tool, it would not prevent hosts from communicating with each other. Dynamic Trunking Protocol (DTP) is a Cisco proprietary protocol used to manage automatic trunk negotiation. Disabling DTP would create further issues, as the trunk link would be disabled. Disabling RSTP would not prevent hosts from communicating with each other unless there was a loop involved.
For a trunk link to be established, both ends of the trunk link must be configured to use the same native VLAN. Cisco Discovery Protocol (CDP) will present a native VLAN mismatch error message if the native VLANs do not match. To display the status of the trunk and the native VLAN used on that trunk link, and to verify trunk establishment, you can use the show interface trunk command in privileged EXEC mode.

Cisco Discovery Protocol (CDP) exchanges hardware and software device information with its directly connected CDP neighbors. Although this is a useful troubleshooting tool, it would not prevent hosts from communicating with each other. Dynamic Trunking Protocol (DTP) is a Cisco proprietary protocol used to manage automatic trunk negotiation. Disabling DTP would create further issues, as the trunk link would be disabled. Disabling RSTP would not prevent hosts from communicating with each other unless there was a loop involved.
For a trunk link to be established, both ends of the trunk link must be configured to use the same native VLAN. Cisco Discovery Protocol (CDP) will present a native VLAN mismatch error message if the native VLANs do not match. To display the status of the trunk and the native VLAN used on that trunk link, and to verify trunk establishment, you can use the show interface trunk command in privileged EXEC mode.

Cisco Discovery Protocol (CDP) exchanges hardware and software device information with its directly connected CDP neighbors. Although this is a useful troubleshooting tool, it would not prevent hosts from communicating with each other. Dynamic Trunking Protocol (DTP) is a Cisco proprietary protocol used to manage automatic trunk negotiation. Disabling DTP would create further issues, as the trunk link would be disabled. Disabling RSTP would not prevent hosts from communicating with each other unless there was a loop involved.

To verify that you have properly configured a RIPv2 route, you enter the show ip route command. In our example, the RIPv2 route would have been configured on Router A as this router needs to know how to access resources located in the 172.16.1.0 network. This command will display all entries in the routing table. RIPv2 routes are denoted with the code "R" in the first category of the routing table. To the right of this, you will find information related to the network address and subnet mask of the configured route, including the IP address of the next-hop router or exit interface. The show ip arp command is used to display the contents of the Address Resolution Protocol (ARP) table. ARP establishes correspondence between network addresses (an IP address, for example) and LAN hardware addresses (Ethernet addresses). The show interfaces command is used to display the status and statistics of all the network interfaces on the router. The show running-config command is used to display the current running configuration that is stored in RAM.
To verify that you have properly configured a RIPv2 route, you enter the show ip route command. In our example, the RIPv2 route would have been configured on Router A as this router needs to know how to access resources located in the 172.16.1.0 network. This command will display all entries in the routing table. RIPv2 routes are denoted with the code "R" in the first category of the routing table. To the right of this, you will find information related to the network address and subnet mask of the configured route, including the IP address of the next-hop router or exit interface. The show ip arp command is used to display the contents of the Address Resolution Protocol (ARP) table. ARP establishes correspondence between network addresses (an IP address, for example) and LAN hardware addresses (Ethernet addresses). The show interfaces command is used to display the status and statistics of all the network interfaces on the router. The show running-config command is used to display the current running configuration that is stored in RAM.
To verify that you have properly configured a RIPv2 route, you enter the show ip route command. In our example, the RIPv2 route would have been configured on Router A as this router needs to know how to access resources located in the 172.16.1.0 network. This command will display all entries in the routing table. RIPv2 routes are denoted with the code "R" in the first category of the routing table. To the right of this, you will find information related to the network address and subnet mask of the configured route, including the IP address of the next-hop router or exit interface. The show ip arp command is used to display the contents of the Address Resolution Protocol (ARP) table. ARP establishes correspondence between network addresses (an IP address, for example) and LAN hardware addresses (Ethernet addresses). The show interfaces command is used to display the status and statistics of all the network interfaces on the router. The show running-config command is used to display the current running configuration that is stored in RAM.

A loopback interface is a virtual interface that resides on a router. It is not connected to any other device. Loopback interfaces are very useful because they will never go "down," unless the entire router goes down. This helps in managing routers because there will always be at least one active interface on the routers-the loopback interface. To create a loopback interface, all you need to do is enter the configuration mode for the interface. Optionally, you may add an IP address. The range of addresses that are reserved for loopback addresses are 127.0.0.1 to 127.255.255.255.0
A loopback interface is a virtual interface that resides on a router. It is not connected to any other device. Loopback interfaces are very useful because they will never go "down," unless the entire router goes down. This helps in managing routers because there will always be at least one active interface on the routers-the loopback interface. To create a loopback interface, all you need to do is enter the configuration mode for the interface. Optionally, you may add an IP address. The range of addresses that are reserved for loopback addresses are 127.0.0.1 to 127.255.255.255.0
A loopback interface is a virtual interface that resides on a router. It is not connected to any other device. Loopback interfaces are very useful because they will never go "down," unless the entire router goes down. This helps in managing routers because there will always be at least one active interface on the routers-the loopback interface. To create a loopback interface, all you need to do is enter the configuration mode for the interface. Optionally, you may add an IP address. The range of addresses that are reserved for loopback addresses are 127.0.0.1 to 127.255.255.255.0

On a computer with the Microsoft Windows operating system, the ipconfig command can be used to display all current TCP/IP network configuration values at the command line. Using various parameters, the command can also be used to refresh DHCP and DNS settings. The /release parameter sends a DHCPRELEASE message to the DHCP server. This will release the current DHCP configuration and discard the IP address configuration for all of the adapters that are configured to obtain an IP address automatically. The /renew parameter renews the DHCP configuration for all of the adapters that are configured to obtain an IP address automatically.

The other commands will not refresh the DHCP configuration.
On a computer with the Microsoft Windows operating system, the ipconfig command can be used to display all current TCP/IP network configuration values at the command line. Using various parameters, the command can also be used to refresh DHCP and DNS settings. The /release parameter sends a DHCPRELEASE message to the DHCP server. This will release the current DHCP configuration and discard the IP address configuration for all of the adapters that are configured to obtain an IP address automatically. The /renew parameter renews the DHCP configuration for all of the adapters that are configured to obtain an IP address automatically.

The other commands will not refresh the DHCP configuration.
On a computer with the Microsoft Windows operating system, the ipconfig command can be used to display all current TCP/IP network configuration values at the command line. Using various parameters, the command can also be used to refresh DHCP and DNS settings. The /release parameter sends a DHCPRELEASE message to the DHCP server. This will release the current DHCP configuration and discard the IP address configuration for all of the adapters that are configured to obtain an IP address automatically. The /renew parameter renews the DHCP configuration for all of the adapters that are configured to obtain an IP address automatically.

The other commands will not refresh the DHCP configuration.

A routing table contains a list of all networks that are known to the router and information about how to reach those networks. Each line, or entry, of the routing table lists a destination network and the interface or next-hop address by which that destination network can be reached. When a router receives information about new or changed routes, it updates its own routing table and, in turn, passes the information to other routers.
A routing table contains a list of all networks that are known to the router and information about how to reach those networks. Each line, or entry, of the routing table lists a destination network and the interface or next-hop address by which that destination network can be reached. When a router receives information about new or changed routes, it updates its own routing table and, in turn, passes the information to other routers.
A routing table contains a list of all networks that are known to the router and information about how to reach those networks. Each line, or entry, of the routing table lists a destination network and the interface or next-hop address by which that destination network can be reached. When a router receives information about new or changed routes, it updates its own routing table and, in turn, passes the information to other routers.