Basic Linux Router I

touch@coe.psu.ac.th

Router, a device that ...

•Working on OSI Layer 3 (Network Layer)

•Connected to more than one networks

•Finding a best path to deliver packets

•Forward packets from one network to another

•Can run on either dedicated device or personal computer

Routing.. How it works.

•Default Gateway

•Routing Table

•Routing mechanism

•Static Routing

•Dynamic Routing

Default Gateway•An address for host to deliver

packet to, if source and destination host are not in the same subnet

•Default Gateway Example...

Routing Tables•Kernel IP routing table

•Destination Gateway Genmask Flags Metric Ref Use Iface

•202.12.74.192 0.0.0.0 255.255.255.192 U 0 0 0 eth1

•192.100.77.0 172.30.0.1 255.255.255.0 UG 0 0 0 eth0

•172.30.0.0 0.0.0.0 255.255.252.0 U 0 0 0 eth0

•192.168.0.0 172.30.0.1 255.255.0.0 UG 0 0 0 eth0

•172.16.0.0 172.30.0.1 255.240.0.0 UG 0 0 0 eth0

•0.0.0.0 202.12.74.193 0.0.0.0 UG 0 0 0 eth1

Routing Mechanism

•Static Routing

•Dynamic Routing

•Interior Routing Protocol

•RIP, OSPF, IGRP

•Exterior Routing Protocol

•BGP, EIGRP

Routing Devices•Dedicated Devices

•Enterprise

•Cisco, 3COM, Juniper, Huawei, etc.

•SOHO

•Various broadband router.

•PC based Devices

•Linux Router

Linux Router command• ifconfig [-v] [-a] [-s] [interface]

• route [-CFvnee]

• route [-v] [-A family] add [-net|-host] target [netmask Nm] [gw Gw] [metric N] [mss M] [window W] [irtt I] [reject] [mod] [dyn] [reinstate] [[dev] If]

• route [-v] [-A family] del [-net|-host] target [gw Gw] [netmask Nm] [metric N] [[dev] If]

• route [-V] [--version] [-h] [--help]

Linux Router command

• ping [ -LRUbdfnqrvVaAB] [ -c count] [ -i interval] [ -l preload] [-p pattern] [ -s packetsize] [ -t ttl] [ -w deadline] [ -F flowlabel] [ -I interface] [ -M hint] [ -Q tos] [ -S sndbuf] [ -T timestamp option] [ -W timeout] [ hop ...] destination

• traceroute [ -dFIlnrvx ] [ -f first_ttl ] [ -g gateway ] [ -i iface ] [ -m max_ttl ] [ -p port ] [ -q nqueries ] [ -s src_addr ] [ -t tos ] [ -w waittime ] [ -z pausemsecs ] host [ packetlen ]