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RE:ddd
.1.3.1. Describe the role of host addresses on a routed network.
A host value of 0 means the wire itself
Routing tables contain entries for networks, it usually contains no info on hosts
An Ip address and a subnet mask on an interface achieve three purposes:
- enable the system to process the receipt and transmiddion of packets
- They specify the devices local addres
- they specify a range of addresees that share tha cable with the device
10.1.4.1. Describe the role of broadcast addresses on a routed network.
Directed broadcasts: Broadcasts directed into a specific network/subnet are allowed and are forwarded by the router. These directred broadcast contain all 1s in the host field (255)(FF)
Flooded broadcasts are not propagated but are considered lovcal broadcasts
10.1.5.1. Explain the assignment of router interface and network IP addresses.
The graphic shows a small network with assigned interface addresses, subnet masks, and resulting subnet numbers. The number of routing bits (network and subnet bits) in each subnet mask can also be indicated by the "/n " format.
Example /8=255.0.0.0 /24=255.255.255.0
/27=255.255.255.224
10.2.1.1. Describe ip address command.
ip address xxx.xxx.xxx.xxx(ip add) xxx.xxx.xxx.xxx (mask)
Use the " term ip netmask-format " command to specify the format of network masks for the current session. Options are:
- bit count
- dotted-decimal (default)
- hexadecimal
10.2.2.1. Describe the ip host command.
The " ip host " command makes a static name to address entry in the router's config file
name= any name you prefer to describe the destination
"tcp-port-number " optional number that idents the TCP port to use when using the host name with an EXEC connect or TELNET command. The default is port23 for telnet
" address" ip addrewss where the device can be reached
In the above example:
ip host tokyo 1.0.0.5 2.0.0.8 defines two network address for the host tokyo
ip host kyoto 1.0.0.4 defines kyoto as a name equivalent for the address 1.0.0.4
10.2.3.1. Describe the ip name-server command.
The " ip name-server" command defines which hosts can provide the name services. You can specify a max of 6 IP addresses as name servers in a single command
To map domain names to IP addresses, you must identify the host names, specify a name server, and enable DNS. Any time the OS software recieves a hostname it does not recognize, it refers to DNS to resolve that ip address oif that device
10.2.4.1. Describe how to enable and disable DNS on a router.
Each unique IP address can have a host name assoc with it. The Cisioc IOS sw maintains a cache of host name-to-address mappings for use by exec commands. This cache speeds the process of converting names to addresses.
Ip defines a na,ming scheme that allows a device to be ident by its location in IP. a name such as ftp.cisco.com idents the domain of FTP for Cisco. To keep track of domain names, IP identifes a name server that manages the name cache.
DNS is enabled by default with a server address of 255.255.255.255 which is local broadcast
The " no ip domain-lookup" command turns off name-to-address translation in the router. This means the router will not generate or forward name system broadcast packets.....
The show hosts command is used to display cached host names and addresses
Show Hosts commands:
host names of learned hosts
flag descriptions of how info was learned and current status
perm statitcally configured
temp dns configured
ok entry is current
EX entry expired
age time in hours since software reffered the entry
type protocol field
addresses logical addresses assoc with hoist name
3 comands used to verify address config
telnet verifies app layer software
ping uses ICMP to verify hardware connection
trace uses TTL values to generate medssagesa from each router on path
PING values ! successful, . timed out , U dest unreach, C congestion-experienced packet, I ping interuppted (e.g. Ctrl-Shjift-6 x), ? packet tpye unknown, & packett TTL exceeded
Extended PING - only avail in EXEC mode - used in extended mode to specify Internet header options. To enter extended mode, type ping and Y at extended command prompt
TRACE Supported by IP,CLNS,VINES, and appl;e talk
responses : !H probe was received by router but not forwarded, usually due to an access list, P protocol was unreachable, N- the network was unreachable, U port was unreachable, * time out
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