Ip addressing: dhcp & dns Chapter 5c

objectives Upon completion of this chapter, you should be able to: Configure IP addresses Identify & select valid IP addresses for networks Configure a DHCP server Configure a host to use DHCP for configuration Troubleshoot & resolve IP addresses configuration and communication issues Configure DNS addresses Configure an IPv6 address

Network+ objectives 1.3 Install and configure the following networking services/applications DHCP Static vs dynamic IP addressing Reservations Scopes Leases Options (DNS servers, suffixes) IP helper/DHCP relay DNS DNS servers DNS records (A, MX, AAAA, CNAME, PTR) Dynamic DNS

Dhcp server configuration 5.3 Dhcp server configuration

DHCP Overview IP configuration used to be manual Assign IP, SM, DG, DNS DHCP takes care of that At home, your router is a DHCP server At work, you may have a dedicated DHCP server Used for general purpose/PC devices Static addressing for routers, switches, printers, Internet-accessible devices DHCP addresses are leased for a time period Discuss wi-fi and when you enter another network, DHCP gets your device an IP address, SM, DG, and DNS server addresses. DHCPv6 (DHCP for IPv6) provides similar services for IPv6 clients. One important difference is that DHCPv6 does not provide a default gateway address. This can only be obtained dynamically from the router's Router Advertisement message.

Dhcp everywhere

Dhcp: how it works Discover: where you at? BROADCAST* of all 255’s goes to everyone but only the DHCP server responds Offer: Do you want to use this address? Request: I’d like to use that one. I’m accepting this offer. BROADCAST* ACK: Thanks for shopping! Your lease is finalized. It’s all yours! DORA!!!!!

activity Watch Professor Messer Video DHCP Addressing Overview 5:15 TestOut 5.3.1- Watch the video/script TestOut 5.3.2- Configure a DHCP Server Lab

Dhcp reservations Dynamic Allocation Static Allocation Sever has a pool of addresses DHCP Servers use dynamic allocation Keeps a list of what MAC addresses used each IP address You’ll usually get the same IP address next time Static Allocation You configure an IP address for a specific device (printers, switches, router ports) via MAC Video is to Professor Messer The DHCP Reservations area is where you would assign the range of addresses to be given out or excluded (like don’t give out these addresses because they belong to servers). DHCP Reservations 3:16

Dhcp scopes The pool of addresses you tell it to give out Along with the SM, DG, DNS server address, lease duration, etc. DHCP Scopes 2:10

Dhcp leases Allocated/assigned a lease time If you reboot, it forgets & then requests an IP Reallocation (remember DHCP server keeps list) Lease starts over Timers T1 Checks in with DHCP server to renew lease (still in use) at 50% of lease time T2 If DHCP server lost, it will check in at 7/8 time to hopefully update the time & renew DHCP Leases 4:09 50% of lease time: Example 4 day lease will check in at 2 days 7/8 time: Example 4 day lease checks in at 2 days and it can’t find the DHCP server. It tries again at 3.5 days.

Dhcp options Stuff in addition to IP SM, DG, DNS, lease time Other options include VoIP settings Such as the Call Server IP address for the phone DHCP Options 2:46

activity TestOut 5.3.3- Watch the video/script TestOut 5.3.4- Configure DHCP Options Lab

activity TestOut 5.3.5- Create DHCP Exclusions Lab TestOut 5.3.6- Create DHCP Client Reservations Lab TestOut 5.3.7- Watch the video/script TestOut 5.3.8- Configure a DHCP Client Lab TestOut 5.3.10- Practice Questions (8Q) Complete this in 2-3 days on their own.

5.4 Dhcp relay

Dhcp relay Your DHCP server may be on another subnet Or a backup DHCP server is on another subnet Broadcasts DO NOT pass routers DHCP uses broadcasts (255.255.255.255) DHCP relay Configured on router to pass these broadcasts Sometimes called IP Helper

activity TestOut 5.4.1- Watch the video/script TestOut 5.4.3- Configure a DHCP Relay Agent Lab TestOut 5.4.4- Add a DHCP Server on Another Subnet Lab TestOut 5.4.5- Practice Questions (3Q) Complete in 1 day.

5.5 Dns name resolution

Dns- the beginning Each host is assigned a number (IP address) It’s easier to remember names though Originally, each device had a simple text hosts file that mapped names to numbers It had to be on each device List got to big Hard to update

Dns- now Servers that translates names to IP addresses Local DNS servers know some, forward rest to higher authority DNS servers The main DNS servers are called Root Servers Other companies & ISPs have their own DNS servers that connect to the Root Servers Your PC connects to a DNS server (usually your ISPs) A list of root servers: http://www.iana.org/domains/root/servers Root Servers

How name servers are organized From within GCIT, you want to get to www.umas.edu (the FULLY QUALIFIED DOMAIN NAME- FQDN) Your PC checks its DNS cache. If not there, it goes to your local DNS server (which could be on the GCIT network or at the ISP) and it communicates its findings back to your local DNS server. The local DNS server queries the root server. Root server responds with IP addresses of the TLD servers for .edu’s. and it communicates it back to your local DNS server. The local DNS server requests the info from one of the TLD servers for .edu’s. The TLD server responds with the IP address of the umass.edu authoritative server. Your local DNS server makes the request to the Umass name server which responds with the IP address of the www.umass.edu web server host. Your local DNS server and the client PC store the info in cache so it doesn’t have to ask again. http://maps.google.com (FQDN) COM- top-level domain (TLD) Google- second-level domain Maps- third-level domain (subdomain)

Dns- where it’s set Go to command prompt & type: ipconfig /displaydns displays all cached DNS If a web admin changes the IP address of a server, it gets set in DNS server, and the user has no idea the IP address changed.

Checking dns Nslookup Ipconfig /displaydns Ipconfig /flushdns Get in the mode and then enter domain Ipconfig /displaydns Displays cached DNS Ipconfig /flushdns Removes all cached DNS entries If DNS is not working, you won’t be able to get to websites by their host name, just their IP address.

activity Use nslookup, displaydns, flushdns DNS Overview 6:28 http://www.learndns.com/pdf/dns101.pdf DNS Overview 6:28

In the dns server database DNS server has many records to resolve names Records include name field (domain name), address, type field (type of resource, usually Internet) Common types of DNS records: Type Description A A host’s IPv4 address AAAA A host’s IPv6 address MX Identifies a Mail Server NS Authoritative Name Server CNAME Holds another name for a host CNAME Example: www.gcit.org/parking points to http://www.gcit.org/apps/pages/index.jsp?uREC_ID=277387&type=d Each record in the database has a TTL that says how long it should keep it in cache. DNS Records 5:53

Configuring dns & using this

Review- 3q .edu, .org, and .gov are all what kind of domains? Top-level domains What kind of server is being used if you have to add an MX record to the DNS settings? Mail server A host has been assigned an IP address of 169.254.0.1. What kind of address is this? APIPA

activity Unit 5c DHCP/DNS Packet Tracer Lab

Packet tracer lab Lab 10.2.2.7 Configure static & dynamic DHCP Configure a DNS Server https://static-course-assets.s3.amazonaws.com/ITN51/en/course/files/10.2.2.7%20Packet%20Tracer%20-%20DNS%20and%20DHCP.pdf

activity TestOut 5.5.1- Watch the video/script TestOut 5.5.4- Configure DNS Addresses Lab TestOut 5.5.5- Create Standard DNS Zones Lab TestOut 5.5.6- Create Host Records Lab TestOut 5.5.7- Create CNAME Records Lab TestOut 5.5.8- Troubleshoot DNS Records Lab TestOut 5.5.9- Practice Questions (5Q) Complete in 2-3 days

Ip addressing: dhcp & dns Chapter 5c