Notes on Linux ip Command
iproute2
http://en.wikipedia.org/wiki/Iproute2
iproute2 is a collection of utilities for controlling TCP and UDP IP networking and traffic control in Linux. It is intended to replace an entire suite of legacy Unix networking tools (often called “net-tools”)
Tools replaced by iproute2 are:
* Address and link configuration: ifconfig → ip addr, ip link
* Routing tables: route → ip route
* Neighbors: arp → ip neigh
* Tunnels: iptunnel → ip tunnel
* Multicast: ipmaddr → ip maddr
* netstat → ss
Network Confguration: "ip" Tool
The ip tool provides most of the networking confguration a Linux box needs. You can confgure interfaces, ARP, policy routing, tunnels, etc.
Exploring your current configuration
ip help
ip route add help
ip shows us our links
ip link list
Usage: ip link set DEVICE { up | down | arp { on | off } |
dynamic { on | off } | multicast { on | off } | txqueuelen PACKETS |
name NEWNAME | address LLADDR | broadcast LLADDR | mtu MTU }
ip link show [ DEVICE ]
ip shows us our IP addresses
ip address show
Usage: ip addr {add|del} IFADDR dev STRING
ip addr {show|flush} [ dev STRING ] [ scope SCOPE-ID ]
[ to PREFIX ] [ FLAG-LIST ] [ label PATTERN ]
IFADDR := PREFIX | ADDR peer PREFIX
[ broadcast ADDR ] [ anycast ADDR ]
[ label STRING ] [ scope SCOPE-ID ]
SCOPE-ID := [ host | link | global | NUMBER ]
FLAG-LIST := [ FLAG-LIST ] FLAG
FLAG := [ permanent | dynamic | secondary | primary |
tentative | deprecated ]
With the -statistics option, ip also prints interface statistics: ip -s link ls eth0
If the -s option is entered twice or more, ip prints more detailed statistics on receiver and transmitter errors: ip -s -s link ls eth0
ip shows us our routes
ip route show
Usage: ip route { list | flush } SELECTOR
ip route get ADDRESS [ from ADDRESS iif STRING ]
[ oif STRING ] [ tos TOS ]
ip route { add | del | replace | change | append | replace | monitor } ROUTE
SELECTOR := [ root PREFIX ] [ match PREFIX ] [ exact PREFIX ]
[ table TABLE_ID ] [ proto RTPROTO ]
[ type TYPE ] [ scope SCOPE ]
ROUTE := NODE_SPEC [ INFO_SPEC ]
NODE_SPEC := [ TYPE ] PREFIX [ tos TOS ]
[ table TABLE_ID ] [ proto RTPROTO ]
[ scope SCOPE ] [ metric METRIC ]
INFO_SPEC := NH OPTIONS FLAGS [ nexthop NH ]...
NH := [ via ADDRESS ] [ dev STRING ] [ weight NUMBER ] NHFLAGS
OPTIONS := FLAGS [ mtu NUMBER ] [ advmss NUMBER ]
[ rtt NUMBER ] [ rttvar NUMBER ]
[ window NUMBER] [ cwnd NUMBER ] [ ssthresh REALM ]
[ realms REALM ]
TYPE := [ unicast | local | broadcast | multicast | throw |
unreachable | prohibit | blackhole | nat ]
TABLE_ID := [ local | main | default | all | NUMBER ]
SCOPE := [ host | link | global | NUMBER ]
FLAGS := [ equalize ]
NHFLAGS := [ onlink | pervasive ]
RTPROTO := [ kernel | boot | static | NUMBER ]
ip route add 192.168.55.0/24 via 192.168.1.254 dev eth1
Alternatively, you can use old good route command:
route add -net 192.168.55.0 netmask 255.255.255.0 gw 192.168.1.254 dev eth1
ip route add default via 192.168.1.254
ip route delete 192.168.1.0/24 dev eth0
Route all traffic via 192.168.1.254 gateway connected via eth0 network interface:
ip route add default gw 192.168.1.254 eth0
under Red Hat/Fedora Linux you can add static router for eth0 network interface by editing /etc/sysconfig/network-scripts/route-eth0 file. Under Debian Linux add static route by editing /etc/network/interface file.
ARP
ip neigh show
Usage: ip neigh { add | del | change | replace } { ADDR [ lladdr LLADDR ]
[ nud { permanent | noarp | stale | reachable } ]
| proxy ADDR } [ dev DEV ]
ip neigh {show|flush} [ to PREFIX ] [ dev DEV ] [ nud STATE ]
ip neigh delete 9.3.76.43 dev eth0
ip monitor and rtmon - state monitoring
Usage: ip monitor [ all | LISTofOBJECTS ]
LISTofOBJECTS may contain link, address and route.
Multicast routing
Add the Multicast virtual network:
ip route add 224.0.0.0/4 dev eth0
Now, tell Linux to forward packets...
echo 1 > /proc/sys/net/ipv4/ip_forward
To test our connection, we ping the default group, 224.0.0.1, to see if anyone is alive. All machines on your LAN with multicasting enabled should respond, but nothing else.
Resources:
http://en.wikipedia.org/wiki/Iproute2
http://www.cyberciti.biz/tips/configuring-static-routes-in-debian-or-red-hat-linux-systems.html
Designing and Implementing Linux Firewalls with QoS using netfilter, iproute2, NAT and L7-filter
