computer system administration
DESCRIPTION
Lecture 4 Networking Startup/DNS. Computer System Administration. Networking Initialization: IRIX. Hostname /etc/sys_id IP Address /etc/hosts nsswitch.conf Netmask /etc/config/ifconfig-1.options Default route /etc/config/static-route.options. /etc/config/ifconfig-1.options. - PowerPoint PPT PresentationTRANSCRIPT
2/26/2003Lecture 4
Computer System Administration
Lecture 4Networking Startup/DNS
2/26/2003Lecture 4
Networking Initialization: IRIX
● Hostname– /etc/sys_id
● IP Address– /etc/hosts
● nsswitch.conf
● Netmask– /etc/config/ifconfig-1.options
● Default route– /etc/config/static-route.options
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/etc/config/ifconfig-1.options
● Appended to ifconfig command for first interface– netmask 0xffffff00
● 255.255.255.0● /24
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/etc/config/static-route.options
● Script file, multiple routing commands can be added– $ROUTE $QUIET add default 128.213.30.1
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IRIX: Multiple Interfaces
● Hostname-INTERFACE– /etc/hosts
● irix-1-ec0.sysadmin.cs.rpi.edu
– /etc/config/ifconfig-#.options● Netmasks, etc.. for additional controllers
– /etc/config/static-route.options● Add additional $ROUTE lines
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Solaris: Networking Startup
● Hostname– /etc/hostname.INTERFACE
● Machine hostname from primary interface
● IP Address– /etc/hosts
● /etc/nsswitch.conf
● Netmask– /etc/netmasks
● Default Route– /etc/defaultrouter
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Solaris: Multiple Interfaces
● Hostnames– /etc/hostname.INTERFACE
● Only primary interface sets global hostname
● IP Address– /etc/hosts
● Netmask– /etc/netmasks
● Static routes– Create your own startup script using route(1)
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FreeBSD: Networking Startup
● All in /etc/rc.conf● Hostname
– hostname=”hostname”● IPAddress/Netmask
– ifconfig_INTERFACE=”inet address netmask netmask”
● Default Route– defaultrouter=”address”
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FreeBSD: Multiple Interfaces
● All in /etc/rc.conf– No need to reset hostname
● IP addresses– Additional ifconfig_INTERFACE lines
● Static routes– static_routes=”name1 name2...”– route_name1=”route(8) args”
● route add ${route_name1}
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DNS: Client Configuration
● /etc/nsswitch.conf– IRIX/Solaris/FreeBSD5+/Many Linux Distributions– hosts:
● files– /etc/hosts
● dns– DNS
● nis– YP/NIS
– Man(1)-page!
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DNS: Resolver
● /etc/resolv.conf– domain
● Default appended to end of most requests.
– search● List of possible extensions to requests
– Mutually exclusive– nameserver
● Can be listed multiple times● Adds additional servers to the ones queried
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Libresolv and state
● resolver library is stateless/unshared– Failed nameservers keep being tried, with delay
● Name Service Caching– Keeps state of servers– Solaris
● nscd– Name Service Cache Daemon
– Irix● nsd
– Name Service Daemon
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DNS: 2 Databases
● Name to address (Forward)– Registrars
● Verisign, EDUCause, etc...
– edu/com/net/org/biz/cc/...● Address to name (reverse)
– NICs● ARIN/APNIC/RIPE
– in-addr.arpa.
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DNS Hierarchies (forward)
.
EduCom Arpa
RPI
CS
MITMicrosoft In-addr
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IP Delegations (reverse)
ICANN
IANA
ARIN APNIC RIPE
AOL
You
RPICS
Registrars
Verisign Educause
RPICS
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Forward
● Forward– Delegated on “.” boundaries– Bottom up
● edu is the most broad● then rpi is more specific● then cs● Etc.
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vs. Reverse
● Reverse– Delegated on “.” boundaries– Top down.
● 128.213 is the most broad (classes!)● 30 is more specific● 2 is a given host.
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IP Classes
● Class based IP routing– A
● 127 class A addresses, each address has 16.7million IPs– /8– All addresses begin (bitwise) 0
– B● ~50,000 class B addresses, each address has 65536 Ips
– /16– All Addresses begin (bitwise) 10
– C● Many, 256 Ips, /24, begin “110”
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Classless Routing
● Poor utilization of IP addresses– Class A addresses largely wasted.
● Allows for almost arbitrary sized networks– 24.a.b.c no longer 1 network
● 24.5.7.x/24● 24.6.x.y/16● 24.8.0.0-24.9.255.255/17● 128.213.30.16-128.213.30.31/28
● Much more load on routers
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DNS: Start of Authority
● SOA– Required to delegate a domain– Fields to specify maintainership of a domain
● Authoritative server● Authoritative email (in DNS format)● Serial number● Refresh● Retry● Expire (TTL)● Minimum
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DNS: Other records
● NS: NameServer– IN NS name
● A: Address– IN NS IP_Address
● MX: Mail Exchange– IN MX priority name
● TXT: Text– IN TXT “data”
● RP: Responsible Person, points to a TXT
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DNS: Other Records
● CNAME (alias)– IN CNAME name– Cannot be combined with types other than A and
PTR● PTR (Pointer) (reverse DNS)
– IN PTR name● AAAA/A6
– 2 types of IPv6 address● AAAA: raw, undelegated. A6: delegated
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Reverse Lookup
● Reverse (literally) lookup– IP Address must be reversed so it too is in bottom-up
order.– Name-to-address:
● monica.cs.rpi.edu 128.213.7.2
– Address-to-name:● 2.7.213.128.in-addr.arpa monica.cs.rpi.edu
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DNS: Forward Example@ IN SOA turing.cs.rpi.edu. labstaff.cs.rpi.edu. (
200302253 ;Serial86400
;Refresh3600 ;Retry604800 ;Expire
(TTL)86400 )
;Minimumlabstaff IN TXT “Department of Computer Science”
IN NS turing.cs.rpi.edu.IN NS stumble.cs.rpi.edu.IN NS netserv1.its.rpi.edu.
turing IN A 128.213.1.1IN MX 1 mumble.cs.rpi.edu.
stumble IN A 128.213.8.7IN MX 1 mumble.cs.rpi.edu.
netserv1.its.rpi.edu. IN A 128.113.1.5www IN CNAME stumble
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DNS: Reverse Example
@ IN SOA turing.cs.rpi.edu. labstaff.cs.rpi.edu. (
20030221386400360060480086400 )
IN NS turing.cs.rpi.edu.IN NS stumble.cs.rpi.edu.IN NS netserv1.its.rpi.edu.
2.7 IN PTR monica.cs.rpi.edu.1.1 IN PTR turing.cs.rpi.edu.18.30 IN PTR irix-1.sysadmin.cs.rpi.edu.
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DNS: Forward Delegationdelegate IN NS their.name.server.
IN NS their-secondary.name.server.their.name.server IN A addresstheir-secondary.name.server IN A address
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DNS: Reverse Delegation24 IN NS their.name.server.
;must be in fwdIN NS their-
secondary.name.server. ;must be in fwd
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DNS: Classless Reverse Delegation
● Delegating reverse DNS when not on “.” boundaries– RFC 2317– Clever and painfull use of CNAMEs(aliases)– Create new level of DNS in reverse and alias all
reverse IPs to that.
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DNS: Classless Reverse Delegation, Delegator
; using delegation of 128.213.30.16/28 as an example16/28 IN NS group-1-dns.sysadmin.cs.rpi.edu.
IN NS group-1-secondary-dns.sysadmin.cs.rpi.edu.16 IN CNAME 16.16/28.30.213.128.in-addr.arpa.17 IN CNAME 17.16/28.30.213.128.in-addr.arpa.18 IN CNAME 18.16/28.30.213.128.in-addr.arpa.19 IN CNAME 19.16/28.30.213.128.in-addr.arpa.20 IN CNAME 20.16/28.30.213.128.in-addr.arpa.21 IN CNAME 21.16/28.30.213.128.in-addr.arpa.
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DNS: Classless Reverse Delegation, Delegate-ed
$ORIGIN 16/28.30.213.128.in-addr.arpa16 IN PTR net.group1.sysadmin.cs.rpi.edu.17 IN PTR router.group1.sysadmin.cs.rpi.edu.18 IN PTR irix.group1.sysadmin.cs.rpi.edu.19 IN PTR solaris.group1.sysadmin.cs.rpi.edu.20 IN PTR freebsd.group1.sysadmin.cs.rpi.edu.
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DNS: Server Configuration
● Type of server– Master– Slave– Cache
● Zone Config files– Forward– Reverse– hints
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named.confacl transferers {
128.213.0.0/16; 128.113.0.0/16; 1.2.3.4; };acl local {128.213.0.0/16; 128.113.0.0/16};acl evil {2.3.4.5;};options {
directory “/etc/namedb”;allow-transfer { transferers; };allow-recursion { local; };blackhole { evil; };recursion no;
};zone “vassar.edu” {
type slave;file “slave/vassar.edu”;masters { 143.229.1.6; };
};
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Named.conf (cont)Zone “.” { /* sets the default $ORIGIN */
type hint;file “named.root”; /*file of root “.” name servers.
};zone “213.128.in-addr.arpa” { type master; file “master/cs.rpi.edu.rev”; also-notify { 128.213.8.7; 128.113.1.3; }};zone “cs.rpi.edu” {
type master;file “master/cs.rpi.edu”;also-notify { 128.213.8.7; 128.113.1.3; }
};
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named/bind operations
● $ORIGIN– Changes suffix appended to all unqualified names
● $GENERATE– Used to make series of hosts– Forward
● $GENERATE 100-200 d11-$.dyn IN A 128.213.11.$
– Reverse● $GENERATE 100-200 $.11 IN PTR d11-$.cs.rpi.edu.
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Name-Server Packages● Solaris
– bind8● SUNWcsu
– Core System Utilities– Already installed
– Bind9● http://www.sunfreeware.com/programlistsparc9.html#bind9
● SGI/Irix– Bind8 included– Bind9
● http://www.sunfreeware.com/programlistsparc9.html#bind9
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Name Server Packages(cont)
● FreeBSD– Bind8: Included– Bind9
● pkg_add -r bind9
● Remember to make sure it starts automatically!
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Group Names
● foo.group-name.sysadmin.cs.rpi.edu● Existing names will be going away
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Next Lecutre
● NIS!