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This chapter describes how to configure the Domain Name Server (DNS) client and enable the Dynamic Host Configuration Protocol version 4 (DHCPv4) client on the Cisco 1000 Series Connected Grid Routers (hereafter referred to as the Cisco CG-OS router). The system software for the Cisco CG-OS router is identified as the Cisco CG-OS software.
This chapter includes the following sections:
•Information About IP Services
This section includes the following topics:
When your network devices require connectivity with devices in networks for which you do not control the name assignment, you can assign device names that uniquely identify your devices within the entire internetwork using the domain name server (DNS). DNS uses a hierarchical scheme for establishing host names for network nodes, which allows local control of the segments of the network through a client-server scheme. The DNS system can locate a network device by translating the hostname of the device into its associated IP address.
On the Internet, a domain is a portion of the naming hierarchy tree that refers to general groupings of networks based on the organization type or geography. Domain names are pieced together with periods (.) as the delimiting characters. For example, Cisco is a commercial organization that the Internet identifies by a com domain, so its domain name is cisco.com. A specific hostname in this domain, the File Transfer Protocol (FTP) system, for example, is identified as ftp.cisco.com.
Name servers keep track of domain names and know the parts of the domain tree for which they have complete information. A name server might also store information about other parts of the domain tree. To map domain names to IP addresses on the Cisco CG-OS router, you must identify the hostnames, specify a name server, and enable the DNS service.
The Cisco CG-OS software allows you to statically map IP addresses to domain names. You can also configure the Cisco CG-OS software to use one or more domain name servers to find an IP address for a host name.
A name server handles client-issued queries to the DNS server for locally defined hosts within a particular zone as follows:
•An authoritative name server responds to DNS user queries for a domain name that is under its zone of authority by using the permanent and cached entries in its own host table. When the query is for a domain name that is under its zone of authority but for which it does not have any configuration information, the authoritative name server replies that no such information exists.
•A name server that is not configured as the authoritative name server responds to DNS user queries by using information that it has cached from previously received query responses. When no
Cisco CG-OS router is configured as the authoritative name server for a zone, queries to the DNS server for locally defined hosts receive nonauthoritative responses.
Name servers answer DNS queries (forward incoming DNS queries or resolve internally generated DNS queries) according to the forwarding and lookup parameters configured for the specific domain.
The Cisco CG-OS router supports stateless restarts for the DNS client. After a system reboot, the
Cisco CG-OS software applies the running configuration.
DHCP client version 4 (DHCPv4) support is enabled on a per interface basis on the Cisco CG-OS router for automatic IPv4 address assignment.
The DHCPv4 server, which supplies the IP addresses to the Cisco CG-OS router interfaces, does not need to be on the same subnet as the Cisco CG-OS router. However, when the DHCPv4 server and
the Cisco CG-OS router are on different subnets, DHCPv4 relay must be active in the network. Generally, DHCPv4 relay is configured on a router in the path between the Cisco CG-OS router and the DHCPv4 server.
DNS
You must have a DNS name server accessible to the Cisco CG-OS router.
DHCPv4
You must have a DHCPv4 server accessible to the Cisco CG-OS router.
When the Cisco CG-OS router and the DHCPv4 server are on different subnets, DHCPv4 relay must be enabled on a router in the path between the Cisco CG-OS router and the DHCPv4 server.
DHCPv4
DHCPv4 server must be active in the network before you install the Cisco CG-OS router when you employ DHCPv4 client for interface IP address assignment.
DNS
DNS Security Extension (DNSSEC) is not supported on the Cisco CG-OS router.
Table 4-1 lists the default settings for IP Services parameters.
|
|
---|---|
DNS client |
Enabled |
DHCPv4 server |
Disabled |
This section includes the following topics:
•Enabling DHCPv4 on Interfaces
You can configure the DNS client to use a DNS server on your network.
Ensure that you have a domain name server on your network.
This example shows how to configure a default domain name and enable DNS lookup.
router# configure terminal
router(config)# ip host cisco-rtp 192.0.2.1
router(config)# ip domain-name myserver.com
router(config)# ip domain-list mycompany.com
router(config)# copy running-config startup-config
Verify that the Cisco CG-OS router has access to the DHCPv4 server.
This example shows how to enable DHCPv4 client on a specific interface.
router# configure terminal
router(config)# interface wimax 3/1
router(config-if)# ip address dhcp
router(config-if)# copy running-config startup-config
To display the DNS client configuration, enter the following command:
DNS Client
This example shows how to establish a domain list with several alternate domain names.
ip domain-list csi.com
ip domain-list telecomprog.edu
ip domain-list merit.edu
This example shows how to locate local name servers, configure the hostname-to-address mapping, configure the addresses of the two name servers, and the default domain name.
ip domain lookup
ip name-server 192.168.1.111 192.168.1.2
ip domain-name cisco.com
DHCPv4 Client
This example shows how to enable DHCPv4 client on a specific interface.
router# configure terminal
router(config)# interface ethernet 3/1
router(config-if)# ip address dhcp
router(config-if)# copy running-config startup-config